From fc1c3c68085775f1ff420d53f1c9da0ba26f10e1 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sun, 27 Feb 2022 16:27:02 +0100
Subject: [PATCH] working on altered pipe syntax

---
 .../src/prog8/codegen/cpu6502/AsmGen.kt       | 100 +++--
 .../codegen/cpu6502/FunctionCallAsmGen.kt     |  58 ---
 .../src/prog8/codegen/target/Encoder.kt       |   6 +-
 .../optimizer/ConstantIdentifierReplacer.kt   |   3 +-
 .../prog8/optimizer/ExpressionSimplifier.kt   |  60 +--
 compiler/src/prog8/compiler/Compiler.kt       |   2 +-
 compiler/src/prog8/compiler/ErrorReporter.kt  |   7 +-
 .../compiler/astprocessing/AstChecker.kt      | 121 ++----
 .../compiler/astprocessing/AstExtensions.kt   |   4 +-
 .../astprocessing/AstIdentifiersChecker.kt    |  15 +-
 .../compiler/astprocessing/AstPreprocessor.kt |  83 +++--
 .../astprocessing/BeforeAsmAstChanger.kt      |  10 +-
 .../astprocessing/VerifyFunctionArgTypes.kt   | 143 +++++++-
 compiler/test/ModuleImporterTests.kt          |   4 +-
 compiler/test/TestAstChecks.kt                |   4 +-
 compiler/test/TestCompilerOnRanges.kt         |   4 +-
 compiler/test/TestPipes.kt                    | 343 ++++++++++++++----
 compiler/test/TestSubroutines.kt              |   8 +-
 .../src/prog8/ast/AstToSourceTextConverter.kt |   2 +-
 compilerAst/src/prog8/ast/AstToplevel.kt      |   2 +-
 compilerAst/src/prog8/ast/base/Base.kt        |   4 +-
 .../prog8/ast/expressions/AstExpressions.kt   |  13 +-
 .../src/prog8/ast/statements/AstStatements.kt |   5 +-
 docs/source/syntaxreference.rst               |  29 +-
 docs/source/todo.rst                          |   3 +-
 examples/test.p8                              |  35 +-
 26 files changed, 654 insertions(+), 414 deletions(-)

diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
index 9c60c2a0e..22f0f01fd 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
@@ -2837,44 +2837,39 @@ $repeatLabel    lda  $counterVar
         }
     }
 
-    internal fun translatePipeExpression(source: Expression, segments: Iterable<FunctionCallExpression>, scope: Node, isStatement: Boolean, pushResultOnEstack: Boolean) {
+    internal fun translatePipeExpression(source: Expression, segments: List<Expression>, scope: Node, isStatement: Boolean, pushResultOnEstack: Boolean) {
 
         // TODO more efficient code generation to avoid needless assignments to the temp var
 
-        TODO("translatePipeExpression")
+        // the source: an expression (could be anything) producing a value.
+        // one or more segment expressions, all are a IFunctionCall node, and LACKING the implicit first argument.
+        // when 'isStatement'=true, the last segment expression should be treated as a funcion call statement (discarding any result value if there is one)
 
-
-/*
-        // the first term: an expression (could be anything) producing a value.
         val subroutine = scope.definingSubroutine!!
-        val firstTerm = expressions.first()
-        var valueDt = firstTerm.inferType(program).getOrElse { throw FatalAstException("invalid dt") }
+        var valueDt = source.inferType(program).getOrElse { throw FatalAstException("invalid dt") }
         var valueSource: AsmAssignSource =
-            if(firstTerm is IFunctionCall) {
-                val resultReg = returnRegisterOfFunction(firstTerm.target, listOf(valueDt))
-                assignExpressionToRegister(firstTerm, resultReg, valueDt in listOf(DataType.BYTE, DataType.WORD, DataType.FLOAT))
+            if(source is IFunctionCall) {
+                val resultReg = returnRegisterOfFunction(source.target, listOf(valueDt))
+                assignExpressionToRegister(source, resultReg, valueDt in listOf(DataType.BYTE, DataType.WORD, DataType.FLOAT))
                 AsmAssignSource(SourceStorageKind.REGISTER, program, this, valueDt, register = resultReg)
             } else {
-                AsmAssignSource.fromAstSource(firstTerm, program, this)
+                AsmAssignSource.fromAstSource(source, program, this)
             }
 
-        // the 2nd to N-1 terms: unary function calls taking a single param and producing a value.
+        // the segments (except the last one): unary function calls taking a single param and producing a value.
         //   directly assign their argument from the previous call's returnvalue.
-        expressions.drop(1).dropLast(1).forEach {
-            valueDt = functioncallAsmGen.translateUnaryFunctionCallWithArgSource(it as IdentifierReference, valueSource, false, subroutine)
-            val resultReg = returnRegisterOfFunction(it, listOf(valueDt))
+        segments.dropLast(1).forEach {
+            it as IFunctionCall
+            valueDt = translateUnaryFunctionCallWithArgSource(it.target, valueSource, false, subroutine)
+            val resultReg = returnRegisterOfFunction(it.target, listOf(valueDt))
             valueSource = AsmAssignSource(SourceStorageKind.REGISTER, program, this, valueDt, register = resultReg)
         }
-
-        // the last term: unary function call taking a single param and optionally producing a result value.
+        // the last segment: unary function call taking a single param and optionally producing a result value.
+        val lastCall = segments.last() as IFunctionCall
         if(isStatement) {
-            // the last term in the pipe, don't care about return var:
-            functioncallAsmGen.translateUnaryFunctionCallWithArgSource(
-                expressions.last() as IdentifierReference, valueSource, true, subroutine)
+            translateUnaryFunctionCallWithArgSource(lastCall.target, valueSource, true, subroutine)
         } else {
-            // the last term in the pipe, regular function call with returnvalue:
-            valueDt = functioncallAsmGen.translateUnaryFunctionCallWithArgSource(
-                expressions.last() as IdentifierReference, valueSource, false, subroutine)
+            valueDt = translateUnaryFunctionCallWithArgSource(lastCall.target, valueSource, false, subroutine)
             if(pushResultOnEstack) {
                 when (valueDt) {
                     in ByteDatatypes -> {
@@ -2890,7 +2885,64 @@ $repeatLabel    lda  $counterVar
                 }
             }
         }
-*/
+    }
+
+    private fun translateUnaryFunctionCallWithArgSource(target: IdentifierReference, arg: AsmAssignSource, isStatement: Boolean, scope: Subroutine): DataType {
+        when(val targetStmt = target.targetStatement(program)!!) {
+            is BuiltinFunctionPlaceholder -> {
+                return if(isStatement) {
+                    translateBuiltinFunctionCallStatement(targetStmt.name, listOf(arg), scope)
+                    DataType.UNDEFINED
+                } else {
+                    translateBuiltinFunctionCallExpression(targetStmt.name, listOf(arg), scope)
+                }
+            }
+            is Subroutine -> {
+                val argDt = targetStmt.parameters.single().type
+                if(targetStmt.isAsmSubroutine) {
+                    // argument via registers
+                    val argRegister = targetStmt.asmParameterRegisters.single().registerOrPair!!
+                    val assignArgument = AsmAssignment(
+                        arg,
+                        AsmAssignTarget.fromRegisters(argRegister, argDt in SignedDatatypes, scope, program, this),
+                        false, program.memsizer, target.position
+                    )
+                    translateNormalAssignment(assignArgument)
+                } else {
+                    val assignArgument: AsmAssignment =
+                        if(functioncallAsmGen.optimizeIntArgsViaRegisters(targetStmt)) {
+                            // argument goes via registers as optimization
+                            val paramReg: RegisterOrPair = when(argDt) {
+                                in ByteDatatypes -> RegisterOrPair.A
+                                in WordDatatypes -> RegisterOrPair.AY
+                                DataType.FLOAT -> RegisterOrPair.FAC1
+                                else -> throw AssemblyError("invalid dt")
+                            }
+                            AsmAssignment(
+                                arg,
+                                AsmAssignTarget(TargetStorageKind.REGISTER, program, this, argDt, scope, register = paramReg),
+                                false, program.memsizer, target.position
+                            )
+                        } else {
+                            // arg goes via parameter variable
+                            val argVarName = asmVariableName(targetStmt.scopedName + targetStmt.parameters.single().name)
+                            AsmAssignment(
+                                arg,
+                                AsmAssignTarget(TargetStorageKind.VARIABLE, program, this, argDt, scope, argVarName),
+                                false, program.memsizer, target.position
+                            )
+                        }
+                    translateNormalAssignment(assignArgument)
+                }
+                if(targetStmt.shouldSaveX())
+                    saveRegisterLocal(CpuRegister.X, scope)
+                out("  jsr  ${asmSymbolName(target)}")
+                if(targetStmt.shouldSaveX())
+                    restoreRegisterLocal(CpuRegister.X)
+                return if(isStatement) DataType.UNDEFINED else targetStmt.returntypes.single()
+            }
+            else -> throw AssemblyError("invalid call target")
+        }
     }
 
     internal fun popCpuStack(dt: DataType, target: VarDecl, scope: Subroutine?) {
diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/FunctionCallAsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/FunctionCallAsmGen.kt
index 028b2a602..a4628c57d 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/FunctionCallAsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/FunctionCallAsmGen.kt
@@ -129,64 +129,6 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
         // remember: dealing with the X register and/or dealing with return values is the responsibility of the caller
     }
 
-    internal fun translateUnaryFunctionCallWithArgSource(target: IdentifierReference, arg: AsmAssignSource, isStatement: Boolean, scope: Subroutine): DataType {
-        when(val targetStmt = target.targetStatement(program)!!) {
-            is BuiltinFunctionPlaceholder -> {
-                return if(isStatement) {
-                    asmgen.translateBuiltinFunctionCallStatement(targetStmt.name, listOf(arg), scope)
-                    DataType.UNDEFINED
-                } else {
-                    asmgen.translateBuiltinFunctionCallExpression(targetStmt.name, listOf(arg), scope)
-                }
-            }
-            is Subroutine -> {
-                val argDt = targetStmt.parameters.single().type
-                if(targetStmt.isAsmSubroutine) {
-                    // argument via registers
-                    val argRegister = targetStmt.asmParameterRegisters.single().registerOrPair!!
-                    val assignArgument = AsmAssignment(
-                        arg,
-                        AsmAssignTarget.fromRegisters(argRegister, argDt in SignedDatatypes, scope, program, asmgen),
-                        false, program.memsizer, target.position
-                    )
-                    asmgen.translateNormalAssignment(assignArgument)
-                } else {
-                    val assignArgument: AsmAssignment =
-                        if(optimizeIntArgsViaRegisters(targetStmt)) {
-                            // argument goes via registers as optimization
-                            val paramReg: RegisterOrPair = when(argDt) {
-                                in ByteDatatypes -> RegisterOrPair.A
-                                in WordDatatypes -> RegisterOrPair.AY
-                                DataType.FLOAT -> RegisterOrPair.FAC1
-                                else -> throw AssemblyError("invalid dt")
-                            }
-                            AsmAssignment(
-                                arg,
-                                AsmAssignTarget(TargetStorageKind.REGISTER, program, asmgen, argDt, scope, register = paramReg),
-                                false, program.memsizer, target.position
-                            )
-                        } else {
-                            // arg goes via parameter variable
-                            val argVarName = asmgen.asmVariableName(targetStmt.scopedName + targetStmt.parameters.single().name)
-                            AsmAssignment(
-                                arg,
-                                AsmAssignTarget(TargetStorageKind.VARIABLE, program, asmgen, argDt, scope, argVarName),
-                                false, program.memsizer, target.position
-                            )
-                        }
-                    asmgen.translateNormalAssignment(assignArgument)
-                }
-                if(targetStmt.shouldSaveX())
-                    asmgen.saveRegisterLocal(CpuRegister.X, scope)
-                asmgen.out("  jsr  ${asmgen.asmSymbolName(target)}")
-                if(targetStmt.shouldSaveX())
-                    asmgen.restoreRegisterLocal(CpuRegister.X)
-                return if(isStatement) DataType.UNDEFINED else targetStmt.returntypes.single()
-            }
-            else -> throw AssemblyError("invalid call target")
-        }
-    }
-
     private fun argumentsViaRegisters(sub: Subroutine, call: IFunctionCall) {
         if(sub.parameters.size==1) {
             argumentViaRegister(sub, IndexedValue(0, sub.parameters.single()), call.args[0])
diff --git a/codeGenTargets/src/prog8/codegen/target/Encoder.kt b/codeGenTargets/src/prog8/codegen/target/Encoder.kt
index 22314b680..5f2aac98a 100644
--- a/codeGenTargets/src/prog8/codegen/target/Encoder.kt
+++ b/codeGenTargets/src/prog8/codegen/target/Encoder.kt
@@ -1,12 +1,12 @@
 package prog8.codegen.target
 
 import com.github.michaelbull.result.fold
-import prog8.ast.base.FatalAstException
 import prog8.codegen.target.cbm.AtasciiEncoding
 import prog8.codegen.target.cbm.IsoEncoding
 import prog8.codegen.target.cbm.PetsciiEncoding
 import prog8.compilerinterface.Encoding
 import prog8.compilerinterface.IStringEncoding
+import prog8.compilerinterface.InternalCompilerException
 
 internal object Encoder: IStringEncoding {
     override fun encodeString(str: String, encoding: Encoding): List<UByte> {
@@ -15,7 +15,7 @@ internal object Encoder: IStringEncoding {
             Encoding.SCREENCODES -> PetsciiEncoding.encodeScreencode(str, true)
             Encoding.ISO -> IsoEncoding.encode(str)
             Encoding.ATASCII -> AtasciiEncoding.encode(str)
-            else -> throw FatalAstException("unsupported encoding $encoding")
+            else -> throw InternalCompilerException("unsupported encoding $encoding")
         }
         return coded.fold(
             failure = { throw it },
@@ -28,7 +28,7 @@ internal object Encoder: IStringEncoding {
             Encoding.SCREENCODES -> PetsciiEncoding.decodeScreencode(bytes, true)
             Encoding.ISO -> IsoEncoding.decode(bytes)
             Encoding.ATASCII -> AtasciiEncoding.decode(bytes)
-            else -> throw FatalAstException("unsupported encoding $encoding")
+            else -> throw InternalCompilerException("unsupported encoding $encoding")
         }
         return decoded.fold(
             failure = { throw it },
diff --git a/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt b/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt
index cec2cc194..6dc325c53 100644
--- a/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt
+++ b/codeOptimizers/src/prog8/optimizer/ConstantIdentifierReplacer.kt
@@ -9,6 +9,7 @@ import prog8.ast.walk.AstWalker
 import prog8.ast.walk.IAstModification
 import prog8.compilerinterface.ICompilationTarget
 import prog8.compilerinterface.IErrorReporter
+import prog8.compilerinterface.InternalCompilerException
 
 // Fix up the literal value's type to match that of the vardecl
 //   (also check range literal operands types before they get expanded into arrays for instance)
@@ -97,7 +98,7 @@ internal class ConstantIdentifierReplacer(private val program: Program, private
                         identifier.parent
                     )
                 )
-                in PassByReferenceDatatypes -> throw FatalAstException("pass-by-reference type should not be considered a constant")
+                in PassByReferenceDatatypes -> throw InternalCompilerException("pass-by-reference type should not be considered a constant")
                 else -> noModifications
             }
         } catch (x: UndefinedSymbolError) {
diff --git a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
index 2082f2374..6e3bdb7af 100644
--- a/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
+++ b/codeOptimizers/src/prog8/optimizer/ExpressionSimplifier.kt
@@ -1,8 +1,6 @@
 package prog8.optimizer
 
-import prog8.ast.IStatementContainer
-import prog8.ast.Node
-import prog8.ast.Program
+import prog8.ast.*
 import prog8.ast.base.DataType
 import prog8.ast.base.FatalAstException
 import prog8.ast.base.IntegerDatatypes
@@ -333,44 +331,26 @@ class ExpressionSimplifier(private val program: Program, private val errors: IEr
         return noModifications
     }
 
-    override fun after(pipeExpr: PipeExpression, parent: Node): Iterable<IAstModification> {
-        require(pipeExpr.segments.isNotEmpty())
-        val segments = pipeExpr.segments
-        if(segments.size==1 && segments[0].isSimple) {
-            // just replace with a normal function call
-            val funcname = segments[1].target
-            val arg = segments[0]
-            val call = FunctionCallExpression(funcname.copy(), mutableListOf(arg), arg.position)
-            return listOf(IAstModification.ReplaceNode(pipeExpr, call, parent))
-        }
-        val firstValue = pipeExpr.source
-        if(firstValue.isSimple) {
-            val funcname = pipeExpr.segments[0].target
-            val first = FunctionCallExpression(funcname.copy(), mutableListOf(firstValue), firstValue.position)
-            val newSegments = mutableListOf(first)
-            newSegments.addAll(pipeExpr.segments.drop(1))
-            return listOf(IAstModification.ReplaceNode(pipeExpr, PipeExpression(first, newSegments, pipeExpr.position), parent))
-        }
-        return noModifications
-    }
+    override fun after(pipeExpr: PipeExpression, parent: Node) = processPipe(pipeExpr, parent)
+    override fun after(pipe: Pipe, parent: Node) = processPipe(pipe, parent)
 
-    override fun after(pipe: Pipe, parent: Node): Iterable<IAstModification> {
-        require(pipe.segments.isNotEmpty())
-        val segments = pipe.segments
-        if(segments.size==1 && segments[0].isSimple) {
-            // just replace with a normal function call
-            val funcname = segments[1].target
-            val arg = segments[0]
-            val call = FunctionCallExpression(funcname.copy(), mutableListOf(arg), arg.position)
-            return listOf(IAstModification.ReplaceNode(pipe, call, parent))
-        }
-        val firstValue = pipe.source
-        if(firstValue.isSimple) {
-            val funcname = pipe.segments[0].target
-            val first = FunctionCallExpression(funcname.copy(), mutableListOf(firstValue), firstValue.position)
-            val newSegments = mutableListOf(first)
-            newSegments.addAll(pipe.segments.drop(1))
-            return listOf(IAstModification.ReplaceNode(pipe, Pipe(first, newSegments, pipe.position), parent))
+    private fun processPipe(pipe: IPipe, parent: Node): Iterable<IAstModification> {
+        if(pipe.source.isSimple) {
+            val segments = pipe.segments
+            if(segments.size==1) {
+                // replace the whole pipe with a normal function call
+                val funcname = (segments[0] as IFunctionCall).target
+                val call = if(pipe is Pipe)
+                    FunctionCallStatement(funcname, mutableListOf(pipe.source), true, pipe.position)
+                else
+                    FunctionCallExpression(funcname, mutableListOf(pipe.source), pipe.position)
+                return listOf(IAstModification.ReplaceNode(pipe as Node, call, parent))
+            } else if(segments.size>1) {
+                // replace source+firstsegment by firstsegment(source) call as the new source
+                val firstSegment = segments.removeAt(0) as IFunctionCall
+                val call = FunctionCallExpression(firstSegment.target, mutableListOf(pipe.source), pipe.position)
+                return listOf(IAstModification.ReplaceNode(pipe.source, call, pipe as Node))
+            }
         }
         return noModifications
     }
diff --git a/compiler/src/prog8/compiler/Compiler.kt b/compiler/src/prog8/compiler/Compiler.kt
index f4dbaa630..c53f22d2d 100644
--- a/compiler/src/prog8/compiler/Compiler.kt
+++ b/compiler/src/prog8/compiler/Compiler.kt
@@ -344,8 +344,8 @@ private fun postprocessAst(program: Program, errors: IErrorReporter, compilerOpt
     program.variousCleanups(errors, compilerOptions)
     val callGraph = CallGraph(program)
     callGraph.checkRecursiveCalls(errors)
+    program.verifyFunctionArgTypes(errors)
     errors.report()
-    program.verifyFunctionArgTypes()
     program.moveMainAndStartToFirst()
     program.checkValid(errors, compilerOptions)          // check if final tree is still valid
     errors.report()
diff --git a/compiler/src/prog8/compiler/ErrorReporter.kt b/compiler/src/prog8/compiler/ErrorReporter.kt
index 2dc864133..5b78b95d5 100644
--- a/compiler/src/prog8/compiler/ErrorReporter.kt
+++ b/compiler/src/prog8/compiler/ErrorReporter.kt
@@ -29,10 +29,10 @@ internal class ErrorReporter: IErrorReporter {
                 MessageSeverity.ERROR -> System.err
             }
             when(it.severity) {
-                MessageSeverity.ERROR -> printer.print("\u001b[91m")  // bright red
-                MessageSeverity.WARNING -> printer.print("\u001b[93m")  // bright yellow
+                MessageSeverity.ERROR -> printer.print("\u001b[91mERROR\u001B[0m ")  // bright red
+                MessageSeverity.WARNING -> printer.print("\u001b[93mWARN\u001B[0m ")  // bright yellow
             }
-            val msg = "${it.severity} ${it.position.toClickableStr()} ${it.message}".trim()
+            val msg = "${it.position.toClickableStr()} ${it.message}".trim()
             if(msg !in alreadyReportedMessages) {
                 printer.println(msg)
                 alreadyReportedMessages.add(msg)
@@ -41,7 +41,6 @@ internal class ErrorReporter: IErrorReporter {
                     MessageSeverity.ERROR -> numErrors++
                 }
             }
-            printer.print("\u001b[0m")      // reset color
         }
         System.out.flush()
         System.err.flush()
diff --git a/compiler/src/prog8/compiler/astprocessing/AstChecker.kt b/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
index fc7f074e7..461b02789 100644
--- a/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
+++ b/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
@@ -546,7 +546,7 @@ internal class AstChecker(private val program: Program,
                 return
             }
             if(decl.value is RangeExpression)
-                throw FatalAstException("range expressions in vardecls should have been converted into array values during constFolding  $decl")
+                throw InternalCompilerException("range expressions in vardecls should have been converted into array values during constFolding  $decl")
         }
 
         when(decl.type) {
@@ -555,7 +555,7 @@ internal class AstChecker(private val program: Program,
                     null -> {
                         // a vardecl without an initial value, don't bother with it
                     }
-                    is RangeExpression -> throw FatalAstException("range expression should have been converted to a true array value")
+                    is RangeExpression -> throw InternalCompilerException("range expression should have been converted to a true array value")
                     is StringLiteral -> {
                         checkValueTypeAndRangeString(decl.datatype, decl.value as StringLiteral)
                     }
@@ -963,7 +963,7 @@ internal class AstChecker(private val program: Program,
 
         val error = VerifyFunctionArgTypes.checkTypes(functionCallExpr, program)
         if(error!=null)
-            errors.err(error, functionCallExpr.position)
+            errors.err(error.first, error.second)
 
         // check the functions that return multiple returnvalues.
         val stmt = functionCallExpr.target.targetStatement(program)
@@ -992,7 +992,14 @@ internal class AstChecker(private val program: Program,
             }
         }
         else if(targetStatement is BuiltinFunctionPlaceholder) {
-            if(builtinFunctionReturnType(targetStatement.name, functionCallExpr.args, program).isUnknown) {
+            val args = if(functionCallExpr.parent is IPipe) {
+                // pipe segment, add implicit first argument
+                val firstArgDt = BuiltinFunctions.getValue(targetStatement.name).parameters.first().possibleDatatypes.first()
+                listOf(defaultZero(firstArgDt, functionCallExpr.position)) + functionCallExpr.args
+            } else {
+                functionCallExpr.args
+            }
+            if(builtinFunctionReturnType(targetStatement.name, args, program).isUnknown) {
                 if(functionCallExpr.parent is Expression || functionCallExpr.parent is Assignment)
                     errors.err("function doesn't return a value", functionCallExpr.position)
             }
@@ -1043,9 +1050,8 @@ internal class AstChecker(private val program: Program,
         }
 
         val error = VerifyFunctionArgTypes.checkTypes(functionCallStatement, program)
-        if(error!=null) {
-            errors.err(error, functionCallStatement.args.firstOrNull()?.position ?: functionCallStatement.position)
-        }
+        if(error!=null)
+            errors.err(error.first, error.second)
 
         super.visit(functionCallStatement)
     }
@@ -1112,6 +1118,19 @@ internal class AstChecker(private val program: Program,
         }
     }
 
+    override fun visit(pipe: PipeExpression) = process(pipe)
+
+    override fun visit(pipe: Pipe) = process(pipe)
+
+    private fun process(pipe: IPipe) {
+        if(pipe.source in pipe.segments)
+            throw InternalCompilerException("pipe source and segments should all be different nodes")
+        if (pipe.segments.isEmpty())
+            throw FatalAstException("pipe is missing one or more expressions")
+        if(pipe.segments.any { it !is IFunctionCall })
+            throw FatalAstException("pipe segments can only be function calls")
+    }
+
     override fun visit(postIncrDecr: PostIncrDecr) {
         if(postIncrDecr.target.identifier != null) {
             val targetName = postIncrDecr.target.identifier!!.nameInSource
@@ -1243,94 +1262,6 @@ internal class AstChecker(private val program: Program,
         super.visit(containment)
     }
 
-    override fun visit(pipe: PipeExpression) {
-        processPipe(pipe.source, pipe.segments, pipe)
-        if(errors.noErrors()) {
-            val last = pipe.segments.last().target
-            when (val target = last.targetStatement(program)!!) {
-                is BuiltinFunctionPlaceholder -> {
-                    if (!BuiltinFunctions.getValue(target.name).hasReturn)
-                        errors.err("invalid pipe expression; last term doesn't return a value", last.position)
-                }
-                is Subroutine -> {
-                    if (target.returntypes.isEmpty())
-                        errors.err("invalid pipe expression; last term doesn't return a value", last.position)
-                    else if (target.returntypes.size != 1)
-                        errors.err("invalid pipe expression; last term doesn't return a single value", last.position)
-                }
-                else -> errors.err("invalid pipe expression; last term doesn't return a value", last.position)
-            }
-            super.visit(pipe)
-        }
-    }
-
-    override fun visit(pipe: Pipe) {
-        processPipe(pipe.source, pipe.segments, pipe)
-        if(errors.noErrors()) {
-            super.visit(pipe)
-        }
-    }
-
-    private fun processPipe(source: Expression, segments: List<FunctionCallExpression>, scope: Node) {
-        // first expression is just any expression producing a value
-        // all other expressions should be the name of a unary function that returns a single value
-        // the last expression should be the name of a unary function whose return value we don't care about.
-        if (segments.isEmpty()) {
-            errors.err("pipe is missing one or more expressions", scope.position)
-        } else {
-            // invalid size and other issues will be handled by the ast checker later.
-            var valueDt = source.inferType(program).getOrElse {
-                throw FatalAstException("invalid dt")
-            }
-
-            for(funccall in segments) {
-                val target = funccall.target.targetStatement(program)
-                if(target!=null) {
-                    when (target) {
-                        is BuiltinFunctionPlaceholder -> {
-                            val func = BuiltinFunctions.getValue(target.name)
-                            if(func.parameters.size!=1)
-                                errors.err("can only use unary function", funccall.position)
-                            else if(!func.hasReturn && funccall !== segments.last())
-                                errors.err("function must return a single value", funccall.position)
-
-                            val paramDts = func.parameters.firstOrNull()?.possibleDatatypes
-                            if(paramDts!=null && !paramDts.any { valueDt isAssignableTo it })
-                                errors.err("pipe value datatype $valueDt incompatible with function argument ${paramDts.toList()}", funccall.position)
-
-                            if(errors.noErrors()) {
-                                // type can depend on the argument(s) of the function. For now, we only deal with unary functions,
-                                // so we know there must be a single argument. Take its type from the previous expression in the pipe chain.
-                                val zero = defaultZero(valueDt, funccall.position)
-                                valueDt = builtinFunctionReturnType(func.name, listOf(zero), program).getOrElse { DataType.UNDEFINED }
-                            }
-                        }
-                        is Subroutine -> {
-                            if(target.parameters.size!=1)
-                                errors.err("can only use unary function", funccall.position)
-                            else if(target.returntypes.size!=1 && funccall !== segments.last())
-                                errors.err("function must return a single value", funccall.position)
-
-                            val paramDt = target.parameters.firstOrNull()?.type
-                            if(paramDt!=null && !(valueDt isAssignableTo paramDt))
-                                errors.err("pipe value datatype $valueDt incompatible with function argument $paramDt", funccall.position)
-
-                            if(target.returntypes.isNotEmpty())
-                                valueDt = target.returntypes.single()
-                        }
-                        is VarDecl -> {
-                            if(!(valueDt isAssignableTo target.datatype))
-                                errors.err("final pipe value datatype can't be stored in pipe ending variable", funccall.position)
-                        }
-                        else -> {
-                            throw FatalAstException("weird function")
-                        }
-                    }
-                }
-            }
-        }
-    }
-
     private fun checkFunctionOrLabelExists(target: IdentifierReference, statement: Statement): Statement? {
         when (val targetStatement = target.targetStatement(program)) {
             is Label, is Subroutine, is BuiltinFunctionPlaceholder -> return targetStatement
diff --git a/compiler/src/prog8/compiler/astprocessing/AstExtensions.kt b/compiler/src/prog8/compiler/astprocessing/AstExtensions.kt
index 27f455edc..4784923a1 100644
--- a/compiler/src/prog8/compiler/astprocessing/AstExtensions.kt
+++ b/compiler/src/prog8/compiler/astprocessing/AstExtensions.kt
@@ -76,8 +76,8 @@ fun Program.desugaring(errors: IErrorReporter): Int {
     return desugar.applyModifications()
 }
 
-internal fun Program.verifyFunctionArgTypes() {
-    val fixer = VerifyFunctionArgTypes(this)
+internal fun Program.verifyFunctionArgTypes(errors: IErrorReporter) {
+    val fixer = VerifyFunctionArgTypes(this, errors)
     fixer.visit(this)
 }
 
diff --git a/compiler/src/prog8/compiler/astprocessing/AstIdentifiersChecker.kt b/compiler/src/prog8/compiler/astprocessing/AstIdentifiersChecker.kt
index 064ac1e5b..a05e47dc9 100644
--- a/compiler/src/prog8/compiler/astprocessing/AstIdentifiersChecker.kt
+++ b/compiler/src/prog8/compiler/astprocessing/AstIdentifiersChecker.kt
@@ -1,6 +1,7 @@
 package prog8.compiler.astprocessing
 
 import prog8.ast.IFunctionCall
+import prog8.ast.IPipe
 import prog8.ast.Node
 import prog8.ast.Program
 import prog8.ast.base.Position
@@ -135,14 +136,24 @@ internal class AstIdentifiersChecker(private val errors: IErrorReporter,
     private fun visitFunctionCall(call: IFunctionCall) {
         when (val target = call.target.targetStatement(program)) {
             is Subroutine -> {
-                if(call.args.size != target.parameters.size) {
+                // if the call is part of a Pipe, the number of arguments in the call should be 1 less than the number of parameters
+                val expectedNumberOfArgs = if(call.parent is IPipe)
+                    target.parameters.size-1
+                else
+                    target.parameters.size
+                if(call.args.size != expectedNumberOfArgs) {
                     val pos = (if(call.args.any()) call.args[0] else (call as Node)).position
                     errors.err("invalid number of arguments", pos)
                 }
             }
             is BuiltinFunctionPlaceholder -> {
                 val func = BuiltinFunctions.getValue(target.name)
-                if(call.args.size != func.parameters.size) {
+                // if the call is part of a Pipe, the number of arguments in the call should be 1 less than the number of parameters
+                val expectedNumberOfArgs = if(call.parent is IPipe)
+                    func.parameters.size-1
+                else
+                    func.parameters.size
+                if(call.args.size != expectedNumberOfArgs) {
                     val pos = (if(call.args.any()) call.args[0] else (call as Node)).position
                     errors.err("invalid number of arguments", pos)
                 }
diff --git a/compiler/src/prog8/compiler/astprocessing/AstPreprocessor.kt b/compiler/src/prog8/compiler/astprocessing/AstPreprocessor.kt
index be6fb552c..2da76e0a4 100644
--- a/compiler/src/prog8/compiler/astprocessing/AstPreprocessor.kt
+++ b/compiler/src/prog8/compiler/astprocessing/AstPreprocessor.kt
@@ -1,15 +1,18 @@
 package prog8.compiler.astprocessing
 
-import prog8.ast.*
+import prog8.ast.IPipe
+import prog8.ast.Node
+import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.*
+import prog8.ast.getTempRegisterName
 import prog8.ast.statements.*
 import prog8.ast.walk.AstWalker
 import prog8.ast.walk.IAstModification
-import prog8.compilerinterface.BuiltinFunctions
 import prog8.compilerinterface.Encoding
 import prog8.compilerinterface.ICompilationTarget
 import prog8.compilerinterface.IErrorReporter
+import prog8.compilerinterface.InternalCompilerException
 
 
 class AstPreprocessor(val program: Program, val errors: IErrorReporter, val compTarget: ICompilationTarget) : AstWalker() {
@@ -112,43 +115,67 @@ class AstPreprocessor(val program: Program, val errors: IErrorReporter, val comp
         return noModifications
     }
 
-    override fun after(pipe: Pipe, parent: Node): Iterable<IAstModification> {
+    override fun before(pipe: Pipe, parent: Node): Iterable<IAstModification> {
+        if(pipe.source is PipeExpression) {
+            // correct Antlr parse tree quirk: turn nested pipe into single flat pipe
+            val psrc = pipe.source as PipeExpression
+            val newSource = psrc.source
+            val newSegments = psrc.segments
+            newSegments += pipe.segments.single()
+            return listOf(IAstModification.ReplaceNode(pipe as Node, Pipe(newSource, newSegments, pipe.position), parent))
+        }
+
         return process(pipe, parent)
     }
 
-    override fun after(pipeExpr: PipeExpression, parent: Node): Iterable<IAstModification> {
+    override fun before(pipeExpr: PipeExpression, parent: Node): Iterable<IAstModification> {
+        if(pipeExpr.source is PipeExpression) {
+            // correct Antlr parse tree quirk; turn nested pipe into single flat pipe
+            val psrc = pipeExpr.source as PipeExpression
+            val newSource = psrc.source
+            val newSegments = psrc.segments
+            newSegments += pipeExpr.segments.single()
+            return listOf(IAstModification.ReplaceNode(pipeExpr as Node, PipeExpression(newSource, newSegments, pipeExpr.position), parent))
+        }
+
         return process(pipeExpr, parent)
     }
 
     private fun process(pipe: IPipe, parent: Node): Iterable<IAstModification> {
+        if(pipe.source is IPipe)
+            throw InternalCompilerException("pipe source should have been adjusted to be a normal expression")
+
+        return noModifications
+
+// TODO don't use artifical inserted args, fix the places that check for arg numbers instead.
         // add the "missing" first argument to each function call in the pipe segments
         // so that all function call related checks just pass
         // might have to remove it again when entering code generation pass, or just replace it there
         // with the proper output value of the previous pipe segment.
-        return pipe.segments.map {
-            val firstArgDt = when (val target = it.target.targetStatement(program)) {
-                is Subroutine -> target.parameters.first().type
-                is BuiltinFunctionPlaceholder -> BuiltinFunctions.getValue(target.name).parameters.first().possibleDatatypes.first()
-                else -> DataType.UNDEFINED
-            }
-            val dummyFirstArg = when (firstArgDt) {
-                in IntegerDatatypes -> {
-                    IdentifierReference(
-                        getTempRegisterName(InferredTypes.InferredType.known(firstArgDt)),
-                        pipe.position
-                    )
-                }
-                DataType.FLOAT -> {
-                    val (name, _) = program.getTempVar(DataType.FLOAT)
-                    IdentifierReference(name, pipe.position)
-                }
-                else -> throw FatalAstException("weird dt")
-            }
 
-            IAstModification.SetExpression(
-                { newexpr -> it.args.add(0, newexpr) },
-                dummyFirstArg, parent
-            )
-        }
+//        val mutations = mutableListOf<IAstModification>()
+//        var valueDt = pipe.source.inferType(program).getOrElse { throw FatalAstException("invalid dt") }
+//        pipe.segments.forEach { call->
+//            val dummyFirstArg = when (valueDt) {
+//                DataType.UBYTE -> FunctionCallExpression(IdentifierReference(listOf("rnd"), pipe.position), mutableListOf(), pipe.position)
+//                DataType.UWORD -> FunctionCallExpression(IdentifierReference(listOf("rndw"), pipe.position), mutableListOf(), pipe.position)
+//                DataType.BYTE, DataType.WORD -> IdentifierReference(
+//                    getTempRegisterName(InferredTypes.InferredType.known(valueDt)),
+//                    pipe.position
+//                ) // there's no builtin function we can abuse that returns a signed byte or word type   // TODO maybe use a typecasted expression around rnd?
+//                DataType.FLOAT -> FunctionCallExpression(IdentifierReference(listOf("rndf"), pipe.position), mutableListOf(), pipe.position)
+//                else -> throw FatalAstException("invalid dt")
+//            }
+//
+//            mutations += IAstModification.SetExpression(
+//                { newexpr -> call.args.add(0, newexpr) },
+//                dummyFirstArg, parent
+//            )
+//
+//            if(call!==pipe.segments.last())
+//                valueDt = call.inferType(program).getOrElse { throw FatalAstException("invalid dt") }
+//        }
+//        return mutations
+
     }
 }
diff --git a/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt b/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt
index af7a001f2..bd44b2146 100644
--- a/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt
+++ b/compiler/src/prog8/compiler/astprocessing/BeforeAsmAstChanger.kt
@@ -16,15 +16,15 @@ internal class BeforeAsmAstChanger(val program: Program,
 ) : AstWalker() {
 
     override fun before(breakStmt: Break, parent: Node): Iterable<IAstModification> {
-        throw FatalAstException("break should have been replaced by goto $breakStmt")
+        throw InternalCompilerException("break should have been replaced by goto $breakStmt")
     }
 
     override fun before(whileLoop: WhileLoop, parent: Node): Iterable<IAstModification> {
-        throw FatalAstException("while should have been converted to jumps")
+        throw InternalCompilerException("while should have been converted to jumps")
     }
 
     override fun before(untilLoop: UntilLoop, parent: Node): Iterable<IAstModification> {
-        throw FatalAstException("do..until should have been converted to jumps")
+        throw InternalCompilerException("do..until should have been converted to jumps")
     }
 
     override fun before(block: Block, parent: Node): Iterable<IAstModification> {
@@ -51,7 +51,7 @@ internal class BeforeAsmAstChanger(val program: Program,
     override fun after(decl: VarDecl, parent: Node): Iterable<IAstModification> {
         if(!options.dontReinitGlobals) {
             if (decl.type == VarDeclType.VAR && decl.value != null && decl.datatype in NumericDatatypes)
-                throw FatalAstException("vardecls for variables, with initial numerical value, should have been rewritten as plain vardecl + assignment $decl")
+                throw InternalCompilerException("vardecls for variables, with initial numerical value, should have been rewritten as plain vardecl + assignment $decl")
         }
 
         return noModifications
@@ -183,7 +183,7 @@ internal class BeforeAsmAstChanger(val program: Program,
 
         if((binExpr.left as? NumericLiteral)?.number==0.0 &&
             (binExpr.right as? NumericLiteral)?.number!=0.0)
-            throw FatalAstException("0==X should have been swapped to if X==0")
+            throw InternalCompilerException("0==X should have been swapped to if X==0")
 
         // simplify the conditional expression, introduce simple assignments if required.
         // NOTE: sometimes this increases code size because additional stores/loads are generated for the
diff --git a/compiler/src/prog8/compiler/astprocessing/VerifyFunctionArgTypes.kt b/compiler/src/prog8/compiler/astprocessing/VerifyFunctionArgTypes.kt
index c6e0d4721..f0055f92d 100644
--- a/compiler/src/prog8/compiler/astprocessing/VerifyFunctionArgTypes.kt
+++ b/compiler/src/prog8/compiler/astprocessing/VerifyFunctionArgTypes.kt
@@ -1,28 +1,35 @@
 package prog8.compiler.astprocessing
 
 import prog8.ast.IFunctionCall
+import prog8.ast.IPipe
+import prog8.ast.Node
 import prog8.ast.Program
 import prog8.ast.base.DataType
+import prog8.ast.base.FatalAstException
+import prog8.ast.base.Position
+import prog8.ast.base.defaultZero
 import prog8.ast.expressions.Expression
 import prog8.ast.expressions.FunctionCallExpression
+import prog8.ast.expressions.PipeExpression
 import prog8.ast.expressions.TypecastExpression
 import prog8.ast.statements.*
 import prog8.ast.walk.IAstVisitor
 import prog8.compilerinterface.BuiltinFunctions
-import prog8.compilerinterface.InternalCompilerException
+import prog8.compilerinterface.IErrorReporter
+import prog8.compilerinterface.builtinFunctionReturnType
 
-internal class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
+internal class VerifyFunctionArgTypes(val program: Program, val errors: IErrorReporter) : IAstVisitor {
 
     override fun visit(functionCallExpr: FunctionCallExpression) {
         val error = checkTypes(functionCallExpr as IFunctionCall, program)
         if(error!=null)
-            throw InternalCompilerException(error)
+            errors.err(error.first, error.second)
     }
 
     override fun visit(functionCallStatement: FunctionCallStatement) {
         val error = checkTypes(functionCallStatement as IFunctionCall, program)
-        if (error!=null)
-            throw InternalCompilerException(error)
+        if(error!=null)
+            errors.err(error.first, error.second)
     }
 
     companion object {
@@ -41,22 +48,27 @@ internal class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
             return false
         }
 
-        fun checkTypes(call: IFunctionCall, program: Program): String? {
+        fun checkTypes(call: IFunctionCall, program: Program): Pair<String, Position>? {
             val argITypes = call.args.map { it.inferType(program) }
             val firstUnknownDt = argITypes.indexOfFirst { it.isUnknown }
             if(firstUnknownDt>=0)
-                return "argument ${firstUnknownDt+1} invalid argument type"
+                return Pair("argument ${firstUnknownDt+1} invalid argument type", call.args[firstUnknownDt].position)
             val argtypes = argITypes.map { it.getOr(DataType.UNDEFINED) }
             val target = call.target.targetStatement(program)
+            val isPartOfPipeSegments = (call.parent as? IPipe)?.segments?.contains(call as Node) == true
             if (target is Subroutine) {
-                if(call.args.size != target.parameters.size)
-                    return "invalid number of arguments (#1)"       // TODO how does this relate to the same error in AstIdentifiersChecker
-                val paramtypes = target.parameters.map { it.type }
-                val mismatch = argtypes.zip(paramtypes).indexOfFirst { !argTypeCompatible(it.first, it.second) }
+                val consideredParamTypes = if(isPartOfPipeSegments) {
+                    target.parameters.drop(1).map { it.type }    // skip first one (the implicit first arg), this is checked elsewhere
+                } else {
+                    target.parameters.map { it.type }
+                }
+                if(argtypes.size != consideredParamTypes.size)
+                    return Pair("invalid number of arguments", call.position)
+                val mismatch = argtypes.zip(consideredParamTypes).indexOfFirst { !argTypeCompatible(it.first, it.second) }
                 if(mismatch>=0) {
                     val actual = argtypes[mismatch].toString()
-                    val expected = paramtypes[mismatch].toString()
-                    return "argument ${mismatch + 1} type mismatch, was: $actual expected: $expected"
+                    val expected = consideredParamTypes[mismatch].toString()
+                    return Pair("argument ${mismatch + 1} type mismatch, was: $actual expected: $expected", call.args[mismatch].position)
                 }
                 if(target.isAsmSubroutine) {
                     if(target.asmReturnvaluesRegisters.size>1) {
@@ -70,7 +82,7 @@ internal class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
                                 else
                                     parent
                             if (checkParent !is Assignment && checkParent !is VarDecl) {
-                                return "can't use subroutine call that returns multiple return values here"
+                                return Pair("can't use subroutine call that returns multiple return values here", call.position)
                             }
                         }
                     }
@@ -78,19 +90,23 @@ internal class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
             }
             else if (target is BuiltinFunctionPlaceholder) {
                 val func = BuiltinFunctions.getValue(target.name)
-                if(call.args.size != func.parameters.size)
-                    return "invalid number of arguments (#2)"    // TODO how does this relate to the same error in AstIdentifiersChecker
-                val paramtypes = func.parameters.map { it.possibleDatatypes }
-                argtypes.zip(paramtypes).forEachIndexed { index, pair ->
+                val consideredParamTypes = if(isPartOfPipeSegments) {
+                    func.parameters.drop(1).map { it.possibleDatatypes }    // skip first one (the implicit first arg), this is checked elsewhere
+                } else {
+                    func.parameters.map { it.possibleDatatypes }
+                }
+                if(argtypes.size != consideredParamTypes.size)
+                    return Pair("invalid number of arguments", call.position)
+                argtypes.zip(consideredParamTypes).forEachIndexed { index, pair ->
                     val anyCompatible = pair.second.any { argTypeCompatible(pair.first, it) }
                     if (!anyCompatible) {
                         val actual = pair.first.toString()
                         return if(pair.second.size==1) {
                             val expected = pair.second[0].toString()
-                            "argument ${index + 1} type mismatch, was: $actual expected: $expected"
+                            Pair("argument ${index + 1} type mismatch, was: $actual expected: $expected", call.args[index].position)
                         } else {
                             val expected = pair.second.toList().toString()
-                            "argument ${index + 1} type mismatch, was: $actual expected one of: $expected"
+                            Pair("argument ${index + 1} type mismatch, was: $actual expected one of: $expected", call.args[index].position)
                         }
                     }
                 }
@@ -99,4 +115,91 @@ internal class VerifyFunctionArgTypes(val program: Program) : IAstVisitor {
             return null
         }
     }
+
+    override fun visit(pipe: PipeExpression) {
+        processPipe(pipe.source, pipe.segments, pipe)
+        if(errors.noErrors()) {
+            val last = (pipe.segments.last() as IFunctionCall).target
+            when (val target = last.targetStatement(program)!!) {
+                is BuiltinFunctionPlaceholder -> {
+                    if (!BuiltinFunctions.getValue(target.name).hasReturn)
+                        errors.err("invalid pipe expression; last term doesn't return a value", last.position)
+                }
+                is Subroutine -> {
+                    if (target.returntypes.isEmpty())
+                        errors.err("invalid pipe expression; last term doesn't return a value", last.position)
+                    else if (target.returntypes.size != 1)
+                        errors.err("invalid pipe expression; last term doesn't return a single value", last.position)
+                }
+                else -> errors.err("invalid pipe expression; last term doesn't return a value", last.position)
+            }
+            super.visit(pipe)
+        }
+    }
+
+    override fun visit(pipe: Pipe) {
+        processPipe(pipe.source, pipe.segments, pipe)
+        if(errors.noErrors()) {
+            super.visit(pipe)
+        }
+    }
+
+    private fun processPipe(source: Expression, segments: List<Expression>, scope: Node) {
+
+        val sourceArg = (source as? IFunctionCall)?.args?.firstOrNull()
+        if(sourceArg!=null && segments.any { (it as IFunctionCall).args.firstOrNull() === sourceArg})
+            throw FatalAstException("some pipe segment first arg is replicated from the source functioncall arg")
+
+        // invalid size and other issues will be handled by the ast checker later.
+        var valueDt = source.inferType(program).getOrElse {
+            throw FatalAstException("invalid dt")
+        }
+
+        for(funccall in segments) {
+            val target = (funccall as IFunctionCall).target.targetStatement(program)
+            if(target!=null) {
+                when (target) {
+                    is BuiltinFunctionPlaceholder -> {
+                        val func = BuiltinFunctions.getValue(target.name)
+                        if(func.parameters.size!=1)
+                            errors.err("can only use unary function", funccall.position)
+                        else if(!func.hasReturn && funccall !== segments.last())
+                            errors.err("function must return a single value", funccall.position)
+
+                        val paramDts = func.parameters.firstOrNull()?.possibleDatatypes
+                        if(paramDts!=null && !paramDts.any { valueDt isAssignableTo it })
+                            errors.err("pipe value datatype $valueDt incompatible with function argument ${paramDts.toList()}", funccall.position)
+
+                        if(errors.noErrors()) {
+                            // type can depend on the argument(s) of the function. For now, we only deal with unary functions,
+                            // so we know there must be a single argument. Take its type from the previous expression in the pipe chain.
+                            val zero = defaultZero(valueDt, funccall.position)
+                            valueDt = builtinFunctionReturnType(func.name, listOf(zero), program).getOrElse { DataType.UNDEFINED }
+                        }
+                    }
+                    is Subroutine -> {
+                        if(target.parameters.size!=1)
+                            errors.err("can only use unary function", funccall.position)
+                        else if(target.returntypes.size!=1 && funccall !== segments.last())
+                            errors.err("function must return a single value", funccall.position)
+
+                        val paramDt = target.parameters.firstOrNull()?.type
+                        if(paramDt!=null && !(valueDt isAssignableTo paramDt))
+                            errors.err("pipe value datatype $valueDt incompatible with function argument $paramDt", funccall.position)
+
+                        if(target.returntypes.isNotEmpty())
+                            valueDt = target.returntypes.single()
+                    }
+                    is VarDecl -> {
+                        if(!(valueDt isAssignableTo target.datatype))
+                            errors.err("final pipe value datatype can't be stored in pipe ending variable", funccall.position)
+                    }
+                    else -> {
+                        throw FatalAstException("weird function")
+                    }
+                }
+            }
+        }
+    }
+
 }
diff --git a/compiler/test/ModuleImporterTests.kt b/compiler/test/ModuleImporterTests.kt
index 55bfa8b31..109fbad0b 100644
--- a/compiler/test/ModuleImporterTests.kt
+++ b/compiler/test/ModuleImporterTests.kt
@@ -204,14 +204,14 @@ class TestModuleImporter: FunSpec({
                     val result = importer.importLibraryModule(filenameNoExt)
                     withClue(count[n] + " call / NO .p8 extension") { result shouldBe null }
                     withClue(count[n] + " call / NO .p8 extension") { errors.noErrors() shouldBe false }
-                    errors.errors.single() shouldContain "0:0) no module found with name i_do_not_exist"
+                    errors.errors.single() shouldContain "0:0: no module found with name i_do_not_exist"
                     errors.report()
                     program.modules.size shouldBe 1
 
                     val result2 = importer.importLibraryModule(filenameWithExt)
                     withClue(count[n] + " call / with .p8 extension") { result2 shouldBe null }
                     withClue(count[n] + " call / with .p8 extension") { importer.errors.noErrors() shouldBe false }
-                    errors.errors.single() shouldContain "0:0) no module found with name i_do_not_exist.p8"
+                    errors.errors.single() shouldContain "0:0: no module found with name i_do_not_exist.p8"
                     errors.report()
                     program.modules.size shouldBe 1
                 }
diff --git a/compiler/test/TestAstChecks.kt b/compiler/test/TestAstChecks.kt
index 46a99b19c..76a2f2211 100644
--- a/compiler/test/TestAstChecks.kt
+++ b/compiler/test/TestAstChecks.kt
@@ -53,8 +53,8 @@ class TestAstChecks: FunSpec({
         compileText(C64Target(), true, text, writeAssembly = true, errors=errors).assertFailure()
         errors.errors.size shouldBe 2
         errors.warnings.size shouldBe 0
-        errors.errors[0] shouldContain ":7:28) assignment value is invalid"
-        errors.errors[1] shouldContain ":8:28) assignment value is invalid"
+        errors.errors[0] shouldContain ":7:28: assignment value is invalid"
+        errors.errors[1] shouldContain ":8:28: assignment value is invalid"
     }
 
     test("can't do str or array expression without using address-of") {
diff --git a/compiler/test/TestCompilerOnRanges.kt b/compiler/test/TestCompilerOnRanges.kt
index 120791b2b..c8b8e09af 100644
--- a/compiler/test/TestCompilerOnRanges.kt
+++ b/compiler/test/TestCompilerOnRanges.kt
@@ -226,8 +226,8 @@ class TestCompilerOnRanges: FunSpec({
             }
         """, errors, false).assertFailure()
         errors.errors.size shouldBe 2
-        errors.errors[0] shouldContain ".p8:5:30) range expression from value must be integer"
-        errors.errors[1] shouldContain ".p8:5:45) range expression to value must be integer"
+        errors.errors[0] shouldContain ".p8:5:30: range expression from value must be integer"
+        errors.errors[1] shouldContain ".p8:5:45: range expression to value must be integer"
     }
 
     test("testForLoopWithIterable_str") {
diff --git a/compiler/test/TestPipes.kt b/compiler/test/TestPipes.kt
index b34715652..f59a790db 100644
--- a/compiler/test/TestPipes.kt
+++ b/compiler/test/TestPipes.kt
@@ -4,20 +4,122 @@ import io.kotest.core.spec.style.FunSpec
 import io.kotest.matchers.shouldBe
 import io.kotest.matchers.string.shouldContain
 import io.kotest.matchers.types.instanceOf
+import prog8.ast.IFunctionCall
+import prog8.ast.Program
+import prog8.ast.base.DataType
+import prog8.ast.base.Position
 import prog8.ast.expressions.*
 import prog8.ast.statements.Assignment
 import prog8.ast.statements.FunctionCallStatement
 import prog8.ast.statements.Pipe
+import prog8.ast.statements.VarDecl
 import prog8.codegen.target.C64Target
-import prog8tests.helpers.ErrorReporterForTests
-import prog8tests.helpers.assertFailure
-import prog8tests.helpers.assertSuccess
-import prog8tests.helpers.compileText
+import prog8.compiler.astprocessing.AstPreprocessor
+import prog8.parser.Prog8Parser.parseModule
+import prog8.parser.SourceCode
+import prog8tests.helpers.*
 
 
 class TestPipes: FunSpec({
 
-    test("correct pipe statements") {
+    test("pipe expression parse tree after preprocessing") {
+        val text = """
+            main {
+                sub start() {
+                    uword xx = 9999 |> func1() |> func2()
+                                    |> func1() |> func2()
+                                    |> func1()
+                }
+                sub func1(uword arg) -> uword {
+                    return arg+1111
+                }
+                sub func2(uword arg) -> uword {
+                    return arg+2222
+                }
+            }
+        """
+        val src = SourceCode.Text(text)
+        val module = parseModule(src)
+        val errors = ErrorReporterForTests()
+        val program = Program("test", DummyFunctions, DummyMemsizer, DummyStringEncoder)
+        program.addModule(module)
+        val preprocess = AstPreprocessor(program, errors, C64Target())
+        preprocess.visit(program)
+        errors.errors.size shouldBe 0
+        preprocess.applyModifications()
+
+        program.entrypoint.statements.size shouldBe 1
+        val pipe = (program.entrypoint.statements.single() as VarDecl).value as PipeExpression
+        pipe.source shouldBe NumericLiteral(DataType.UWORD, 9999.0, Position.DUMMY)
+        pipe.segments.size shouldBe 5
+        var call = pipe.segments[0] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func1")
+        call.args.size shouldBe 0
+        call = pipe.segments[1] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func2")
+        call.args.size shouldBe 0
+        call = pipe.segments[2] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func1")
+        call.args.size shouldBe 0
+        call = pipe.segments[3] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func2")
+        call.args.size shouldBe 0
+        call = pipe.segments[4] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func1")
+        call.args.size shouldBe 0
+    }
+
+    test("pipe statement parse tree after preprocessing") {
+        val text = """
+            main {
+                sub start() {
+                    9999 |> func1() |> func2()
+                             |> func1() |> func2()
+                             |> func3()
+                }
+                sub func1(uword arg) -> uword {
+                    return arg+1111
+                }
+                sub func2(uword arg) -> uword {
+                    return arg+2222
+                }
+                sub func3(uword arg) {
+                    ; nothing
+                }
+            }
+        """
+        val src = SourceCode.Text(text)
+        val module = parseModule(src)
+        val errors = ErrorReporterForTests()
+        val program = Program("test", DummyFunctions, DummyMemsizer, DummyStringEncoder)
+        program.addModule(module)
+        val preprocess = AstPreprocessor(program, errors, C64Target())
+        preprocess.visit(program)
+        errors.errors.size shouldBe 0
+        preprocess.applyModifications()
+
+        program.entrypoint.statements.size shouldBe 1
+        val pipe = program.entrypoint.statements.single() as Pipe
+        pipe.source shouldBe NumericLiteral(DataType.UWORD, 9999.0, Position.DUMMY)
+        pipe.segments.size shouldBe 5
+        var call = pipe.segments[0] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func1")
+        call.args.size shouldBe 0
+        call = pipe.segments[1] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func2")
+        call.args.size shouldBe 0
+        call = pipe.segments[2] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func1")
+        call.args.size shouldBe 0
+        call = pipe.segments[3] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func2")
+        call.args.size shouldBe 0
+        call = pipe.segments[4] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("func3")
+        call.args.size shouldBe 0
+    }
+
+    test("correct pipe statements (no opt)") {
         val text = """
             %import floats
             %import textio
@@ -31,7 +133,6 @@ class TestPipes: FunSpec({
                     9999 |> addword()
                          |> txt.print_uw()
 
-                    ; these are optimized into just the function calls:
                     9999 |> abs() |> txt.print_uw()
                     9999 |> txt.print_uw()
                     99 |> abs() |> txt.print_ub()
@@ -46,20 +147,76 @@ class TestPipes: FunSpec({
                 }
             }
         """
-        val result = compileText(C64Target(), true, text, writeAssembly = true).assertSuccess()
+        val result = compileText(C64Target(), optimize = false, text, writeAssembly = true).assertSuccess()
         val stmts = result.program.entrypoint.statements
         stmts.size shouldBe 7
         val pipef = stmts[0] as Pipe
         pipef.source shouldBe instanceOf<NumericLiteral>()
         pipef.segments.size shouldBe 2
-        pipef.segments[0] shouldBe instanceOf<FunctionCallExpression>()
-        pipef.segments[1] shouldBe instanceOf<IdentifierReference>()
+        var call = pipef.segments[0] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("addfloat")
+        call = pipef.segments[1] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("floats", "print_f")
 
         val pipew = stmts[1] as Pipe
         pipef.source shouldBe instanceOf<NumericLiteral>()
         pipew.segments.size shouldBe 2
-        pipew.segments[0] shouldBe instanceOf<FunctionCallExpression>()
-        pipew.segments[1] shouldBe instanceOf<IdentifierReference>()
+        call = pipew.segments[0] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("addword")
+        call = pipew.segments[1] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("txt", "print_uw")
+
+        stmts[2] shouldBe instanceOf<Pipe>()
+        stmts[3] shouldBe instanceOf<Pipe>()
+        stmts[4] shouldBe instanceOf<Pipe>()
+        stmts[5] shouldBe instanceOf<Pipe>()
+    }
+
+    test("correct pipe statements (with opt)") {
+        val text = """
+            %import floats
+            %import textio
+            
+            main {
+                sub start() {
+
+                    1.234 |> addfloat() 
+                          |> floats.print_f()
+                    
+                    9999 |> addword()
+                         |> txt.print_uw()
+
+                    ; these should be optimized into just the function calls:
+                    9999 |> abs() |> txt.print_uw()
+                    9999 |> txt.print_uw()
+                    99 |> abs() |> txt.print_ub()
+                    99 |> txt.print_ub()
+                }
+
+                sub addfloat(float fl) -> float {
+                    return fl+2.22
+                }
+                sub addword(uword ww) -> uword {
+                    return ww+2222
+                }
+            }
+        """
+        val result = compileText(C64Target(), optimize = true, text, writeAssembly = true).assertSuccess()
+        val stmts = result.program.entrypoint.statements
+        stmts.size shouldBe 7
+        val pipef = stmts[0] as Pipe
+        pipef.source shouldBe instanceOf<FunctionCallExpression>()
+        (pipef.source as IFunctionCall).target.nameInSource shouldBe listOf("addfloat")
+        pipef.segments.size shouldBe 1
+        val callf = pipef.segments[0] as IFunctionCall
+        callf.target.nameInSource shouldBe listOf("floats", "print_f")
+
+        val pipew = stmts[1] as Pipe
+        pipef.source shouldBe instanceOf<FunctionCallExpression>()
+        (pipew.source as IFunctionCall).target.nameInSource shouldBe listOf("addword")
+        pipew.segments.size shouldBe 1
+        val callw = pipew.segments[0] as IFunctionCall
+        callw.target.nameInSource shouldBe listOf("txt", "print_uw")
 
         var stmt = stmts[2] as FunctionCallStatement
         stmt.target.nameInSource shouldBe listOf("txt", "print_uw")
@@ -78,8 +235,8 @@ class TestPipes: FunSpec({
             main {
                 sub start() {
 
-                    1.234 |> addfloat 
-                          |> addword |> addword
+                    1.234 |> addfloat() 
+                          |> addword() |> addword()
                 }
 
                 sub addfloat(float fl) -> float {
@@ -96,21 +253,21 @@ class TestPipes: FunSpec({
         errors.errors[0] shouldContain "incompatible"
     }
 
-    test("correct pipe expressions") {
+    test("correct pipe expressions (no opt)") {
         val text = """
             %import floats
             %import textio
             
             main {
                 sub start() {
-                    float @shared fl = 1.234 |> addfloat 
-                                        |> addfloat
+                    float @shared fl = 1.234 |> addfloat() 
+                                        |> addfloat()
                     
-                    uword @shared ww = 9999 |> addword
-                                        |> addword
+                    uword @shared ww = 9999 |> addword()
+                                        |> addword()
                                         
-                    ubyte @shared cc = 30 |> sin8u |> cos8u     ; will be optimized away into a const number
-                    cc = cc |> sin8u |> cos8u
+                    ubyte @shared cc = 30 |> sin8u() |> cos8u()
+                    cc = cc |> sin8u() |> cos8u()
                 }
 
                 sub addfloat(float fl) -> float {
@@ -119,27 +276,86 @@ class TestPipes: FunSpec({
                 sub addword(uword ww) -> uword {
                     return ww+2222
                 }
-                sub addbyte(ubyte bb) -> ubyte {
-                    return bb+1
-                }
         }
         """
-        val result = compileText(C64Target(), true, text, writeAssembly = true).assertSuccess()
+        val result = compileText(C64Target(), optimize = false, text, writeAssembly = true).assertSuccess()
         val stmts = result.program.entrypoint.statements
         stmts.size shouldBe 8
         val assignf = stmts[1] as Assignment
         val pipef = assignf.value as PipeExpression
         pipef.source shouldBe instanceOf<NumericLiteral>()
         pipef.segments.size shouldBe 2
-        pipef.segments[0] shouldBe instanceOf<FunctionCallExpression>()
-        pipef.segments[1] shouldBe instanceOf<IdentifierReference>()
+        var call = pipef.segments[0] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("addfloat")
+        call = pipef.segments[1] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("addfloat")
+
 
         val assignw = stmts[3] as Assignment
         val pipew = assignw.value as PipeExpression
         pipew.source shouldBe instanceOf<NumericLiteral>()
         pipew.segments.size shouldBe 2
+        call = pipew.segments[0] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("addword")
+        call = pipew.segments[1] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("addword")
+
+        var assigncc = stmts[5] as Assignment
+        val value = assigncc.value as PipeExpression
+        value.source shouldBe NumericLiteral(DataType.UBYTE, 30.0, Position.DUMMY)
+        value.segments.size shouldBe 2
+        call = value.segments[0] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("sin8u")
+        call = value.segments[1] as IFunctionCall
+        call.target.nameInSource shouldBe listOf("cos8u")
+
+        assigncc = stmts[6] as Assignment
+        val pipecc = assigncc.value as PipeExpression
+        pipecc.source shouldBe instanceOf<IdentifierReference>()
+        pipecc.segments.size shouldBe 2
+        pipecc.segments[0] shouldBe instanceOf<BuiltinFunctionCall>()
+        pipecc.segments[1] shouldBe instanceOf<BuiltinFunctionCall>()
+    }
+
+    test("correct pipe expressions (with opt)") {
+        val text = """
+            %import floats
+            %import textio
+            
+            main {
+                sub start() {
+                    float @shared fl = 1.234 |> addfloat() 
+                                        |> addfloat()
+                    
+                    uword @shared ww = 9999 |> addword()
+                                        |> addword()
+                                        
+                    ubyte @shared cc = 30 |> sin8u() |> cos8u()     ; will be optimized away into a const number
+                    cc = cc |> sin8u() |> cos8u()
+                }
+
+                sub addfloat(float fl) -> float {
+                    return fl+2.22
+                }
+                sub addword(uword ww) -> uword {
+                    return ww+2222
+                }
+        }
+        """
+        val result = compileText(C64Target(), optimize = true, text, writeAssembly = true).assertSuccess()
+        val stmts = result.program.entrypoint.statements
+        stmts.size shouldBe 8
+        val assignf = stmts[1] as Assignment
+        val pipef = assignf.value as PipeExpression
+        pipef.source shouldBe instanceOf<FunctionCallExpression>()
+        pipef.segments.size shouldBe 1
+        pipef.segments[0] shouldBe instanceOf<FunctionCallExpression>()
+
+        val assignw = stmts[3] as Assignment
+        val pipew = assignw.value as PipeExpression
+        pipew.source shouldBe instanceOf<FunctionCallExpression>()
+        pipew.segments.size shouldBe 1
         pipew.segments[0] shouldBe instanceOf<FunctionCallExpression>()
-        pipew.segments[1] shouldBe instanceOf<IdentifierReference>()
 
         var assigncc = stmts[5] as Assignment
         val value = assigncc.value as NumericLiteral
@@ -147,43 +363,12 @@ class TestPipes: FunSpec({
 
         assigncc = stmts[6] as Assignment
         val pipecc = assigncc.value as PipeExpression
-        pipecc.source shouldBe instanceOf<NumericLiteral>()
-        pipecc.segments.size shouldBe 2
+        pipecc.source shouldBe instanceOf<BuiltinFunctionCall>()
+        (pipecc.source as BuiltinFunctionCall).target.nameInSource shouldBe listOf("sin8u")
+
+        pipecc.segments.size shouldBe 1
         pipecc.segments[0] shouldBe instanceOf<BuiltinFunctionCall>()
-        pipecc.segments[1] shouldBe instanceOf<IdentifierReference>()
-    }
-
-    test("correct pipe expressions with variables at end") {
-        val text = """
-            %import textio
-            
-            main {
-                sub start() {
-                    uword @shared ww
-                    ubyte @shared cc
-                    
-                    9999 |> addword |> addword |> ww
-                    30 |> sin8u |> cos8u |> cc     ; will be optimized away into a const number
-                }
-                sub addword(uword ww) -> uword {
-                    return ww+2222
-                }
-        }
-        """
-        val result = compileText(C64Target(), true, text, writeAssembly = true).assertSuccess()
-        val stmts = result.program.entrypoint.statements
-        stmts.size shouldBe 7
-
-        val assignw = stmts[4] as Assignment
-        val pipew = assignw.value as PipeExpression
-        pipew.source shouldBe instanceOf<NumericLiteral>()
-        pipew.segments.size shouldBe 2
-        pipew.segments[0] shouldBe instanceOf<FunctionCallExpression>()
-        pipew.segments[1] shouldBe instanceOf<IdentifierReference>()
-
-        val assigncc = stmts[5] as Assignment
-        val value = assigncc.value as NumericLiteral
-        value.number shouldBe 190.0
+        (pipecc.segments[0] as BuiltinFunctionCall).target.nameInSource shouldBe listOf("cos8u")
     }
 
     test("incorrect type in pipe expression") {
@@ -192,8 +377,8 @@ class TestPipes: FunSpec({
             
             main {
                 sub start() {
-                    uword result = 1.234 |> addfloat 
-                                         |> addword |> addword
+                    uword result = 1.234 |> addfloat() 
+                                         |> addword() |> addword()
                 }
 
                 sub addfloat(float fl) -> float {
@@ -218,25 +403,23 @@ class TestPipes: FunSpec({
                 sub start() {
                     uword ww = 9999
                     ubyte bb = 99
-                    ww |> abs |> txt.print_uw
-                    bb |> abs |> txt.print_ub
+                    ww |> abs() |> txt.print_uw()
+                    bb |> abs() |> txt.print_ub()
                 }
             }
         """
         val result = compileText(C64Target(), true, text, writeAssembly = true).assertSuccess()
         val stmts = result.program.entrypoint.statements
         stmts.size shouldBe 7
-        val pipef = stmts[4] as Pipe
-        pipef.source shouldBe instanceOf<NumericLiteral>()
-        pipef.segments.size shouldBe 2
-        pipef.segments[0] shouldBe instanceOf<BuiltinFunctionCall>()
-        pipef.segments[1] shouldBe instanceOf<IdentifierReference>()
+        val pipeww = stmts[4] as Pipe
+        pipeww.source shouldBe instanceOf<BuiltinFunctionCall>()
+        pipeww.segments.size shouldBe 1
+        pipeww.segments[0] shouldBe instanceOf<IFunctionCall>()
 
-        val pipew = stmts[5] as Pipe
-        pipew.source shouldBe instanceOf<NumericLiteral>()
-        pipew.segments.size shouldBe 2
-        pipew.segments[0] shouldBe instanceOf<BuiltinFunctionCall>()
-        pipew.segments[1] shouldBe instanceOf<IdentifierReference>()
+        val pipebb = stmts[5] as Pipe
+        pipebb.source shouldBe instanceOf<BuiltinFunctionCall>()
+        pipebb.segments.size shouldBe 1
+        pipebb.segments[0] shouldBe instanceOf<IFunctionCall>()
     }
 
     test("pipe statement with type errors") {
@@ -246,13 +429,13 @@ class TestPipes: FunSpec({
             main {
                 sub start() {
                     uword ww = 9999
-                    9999 |> abs |> txt.print_ub
-                    ww |> abs |> txt.print_ub
+                    9999 |> abs() |> txt.print_ub()
+                    ww |> abs() |> txt.print_ub()
                 }
             }
         """
         val errors = ErrorReporterForTests()
-        compileText(C64Target(), true, text, writeAssembly = true, errors=errors).assertFailure()
+        compileText(C64Target(), optimize = false, text, writeAssembly = true, errors=errors).assertFailure()
         errors.errors.size shouldBe 2
         errors.errors[0] shouldContain "UWORD incompatible"
         errors.errors[1] shouldContain "UWORD incompatible"
diff --git a/compiler/test/TestSubroutines.kt b/compiler/test/TestSubroutines.kt
index 6b37dbf4d..111bad03e 100644
--- a/compiler/test/TestSubroutines.kt
+++ b/compiler/test/TestSubroutines.kt
@@ -286,8 +286,8 @@ class TestSubroutines: FunSpec({
         val errors = ErrorReporterForTests()
         compileText(C64Target(), false, text, writeAssembly = false, errors=errors).assertFailure()
         errors.errors.size shouldBe 2
-        errors.errors[0] shouldContain "7:25) invalid number of arguments"
-        errors.errors[1] shouldContain "9:25) invalid number of arguments"
+        errors.errors[0] shouldContain "7:25: invalid number of arguments"
+        errors.errors[1] shouldContain "9:25: invalid number of arguments"
     }
 
     test("invalid number of args check on asm subroutine") {
@@ -307,8 +307,8 @@ class TestSubroutines: FunSpec({
         val errors = ErrorReporterForTests()
         compileText(C64Target(), false, text, writeAssembly = false, errors=errors).assertFailure()
         errors.errors.size shouldBe 2
-        errors.errors[0] shouldContain "7:25) invalid number of arguments"
-        errors.errors[1] shouldContain "9:25) invalid number of arguments"
+        errors.errors[0] shouldContain "7:25: invalid number of arguments"
+        errors.errors[1] shouldContain "9:25: invalid number of arguments"
     }
 
     test("invalid number of args check on call to label and builtin func") {
diff --git a/compilerAst/src/prog8/ast/AstToSourceTextConverter.kt b/compilerAst/src/prog8/ast/AstToSourceTextConverter.kt
index 25b80ca5c..21e21b08f 100644
--- a/compilerAst/src/prog8/ast/AstToSourceTextConverter.kt
+++ b/compilerAst/src/prog8/ast/AstToSourceTextConverter.kt
@@ -478,7 +478,7 @@ class AstToSourceTextConverter(val output: (text: String) -> Unit, val program:
         printPipe(pipe.source, pipe.segments)
     }
 
-    private fun printPipe(source: Expression, segments: Iterable<FunctionCallExpression>) {
+    private fun printPipe(source: Expression, segments: Iterable<Expression>) {
         source.accept(this)
         segments.first().accept(this)
         outputln("")
diff --git a/compilerAst/src/prog8/ast/AstToplevel.kt b/compilerAst/src/prog8/ast/AstToplevel.kt
index 557d8eac0..08fd7e926 100644
--- a/compilerAst/src/prog8/ast/AstToplevel.kt
+++ b/compilerAst/src/prog8/ast/AstToplevel.kt
@@ -22,7 +22,7 @@ interface IFunctionCall {
 
 interface IPipe {
     var source: Expression
-    val segments: MutableList<FunctionCallExpression>
+    val segments: MutableList<Expression>       // are all function calls
     val position: Position
     var parent: Node             // will be linked correctly later (late init)
 }
diff --git a/compilerAst/src/prog8/ast/base/Base.kt b/compilerAst/src/prog8/ast/base/Base.kt
index b285f1cde..a8fd66c2d 100644
--- a/compilerAst/src/prog8/ast/base/Base.kt
+++ b/compilerAst/src/prog8/ast/base/Base.kt
@@ -193,8 +193,8 @@ object ParentSentinel : Node {
 data class Position(val file: String, val line: Int, val startCol: Int, val endCol: Int) {
     override fun toString(): String = "[$file: line $line col ${startCol+1}-${endCol+1}]"
     fun toClickableStr(): String {
-        val path = (Path("") / file).absolute().normalize()
-        return "($path:$line:$startCol)"
+        val path = Path(file).absolute().normalize()
+        return "file://$path:$line:$startCol:"
     }
 
     companion object {
diff --git a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
index 954f235a5..1f75449e8 100644
--- a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
+++ b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
@@ -939,6 +939,14 @@ class FunctionCallExpression(override var target: IdentifierReference,
         // lenghts of arrays and strings are constants that are determined at compile time!
         if(target.nameInSource.size>1)
             return null
+
+        // If the function call is part of a Pipe segments, the number of args will be 1 less than the number of parameters required
+        // because of the implicit first argument. We don't know this first argument here. Assume it is not a constant,
+        // which means that this function call cannot be a constant either.
+        val pipeParentSegments = (parent as? IPipe)?.segments ?: emptyList()
+        if(this in pipeParentSegments)
+            return null
+
         val resultValue: NumericLiteral? = program.builtinFunctions.constValue(target.nameInSource[0], args, position)
         if(withDatatypeCheck) {
             val resultDt = this.inferType(program)
@@ -1075,7 +1083,7 @@ class ContainmentCheck(var element: Expression,
 }
 
 class PipeExpression(override var source: Expression,
-                     override val segments: MutableList<FunctionCallExpression>,
+                     override val segments: MutableList<Expression>,        // are all function calls
                      override val position: Position): Expression(), IPipe {
     override lateinit var parent: Node
 
@@ -1099,8 +1107,9 @@ class PipeExpression(override var source: Expression,
         if(node===source) {
             source = replacement
         } else {
+            require(replacement is IFunctionCall)
             val idx = segments.indexOf(node)
-            segments[idx] = replacement as FunctionCallExpression
+            segments[idx] = replacement
         }
     }
 }
diff --git a/compilerAst/src/prog8/ast/statements/AstStatements.kt b/compilerAst/src/prog8/ast/statements/AstStatements.kt
index cb72d4467..fe5780877 100644
--- a/compilerAst/src/prog8/ast/statements/AstStatements.kt
+++ b/compilerAst/src/prog8/ast/statements/AstStatements.kt
@@ -1023,7 +1023,7 @@ class DirectMemoryWrite(var addressExpression: Expression, override val position
 
 
 class Pipe(override var source: Expression,
-           override val segments: MutableList<FunctionCallExpression>,
+           override val segments: MutableList<Expression>,      // are all function calls
            override val position: Position): Statement(), IPipe {
     override lateinit var parent: Node
 
@@ -1043,8 +1043,9 @@ class Pipe(override var source: Expression,
         if(node===source) {
             source = replacement
         } else {
+            require(replacement is IFunctionCall)
             val idx = segments.indexOf(node)
-            segments[idx] = replacement as FunctionCallExpression
+            segments[idx] = replacement
         }
     }
 }
diff --git a/docs/source/syntaxreference.rst b/docs/source/syntaxreference.rst
index e5e69da96..842b2b31c 100644
--- a/docs/source/syntaxreference.rst
+++ b/docs/source/syntaxreference.rst
@@ -528,31 +528,26 @@ containment check:  ``in``
 
 pipe: ``|>``
     Used as an alternative to nesting function calls. The pipe operator is used to 'pipe' the value
-    into the next function. It only works on unary functions (taking a single argument), because you just
-    specify the *name* of the function that the value has to be piped into. The resulting value will be piped
-    into the next function as long as there are chained pipes.
+    into the next function. You write a pipe as a sequence of function calls. You don't write
+    the arguments to the functions though: the value of one segment in the pipe, will be used as the argument
+    for the next function call in the sequence.
+
+    *note:* It only works on unary functions (taking a single argument) for now.
+
     For example, this: ``txt.print_uw(add_bonus(determine_score(get_player(1))))``
     can be rewritten as::
 
         get_player(1)
-            |> determine_score
-            |> add_bonus
-            |> txt.print_uw
+            |> determine_score()
+            |> add_bonus()
+            |> txt.print_uw()
 
-    It also works for expressions that return a value, for example ``uword score = add_bonus(determine_score(get_player(1)))`` ::
+    A pipe can also be written as an expression that returns a value, for example ``uword score = add_bonus(determine_score(get_player(1)))`` ::
 
         uword score = get_player(1)
-                        |> determine_score
-                        |> add_bonus
+                        |> determine_score()
+                        |> add_bonus()
 
-    Finally, if you like the left-to-right flow, it's possible to use the name of a variable as the last term. This just means that the pipe's resulting value is
-    stored in that variable (it's just another way of writing an assignment). So the above can also be written as::
-
-        uword score
-        get_player(1)
-            |> determine_score
-            |> add_bonus
-            |> score
 
 address of:  ``&``
     This is a prefix operator that can be applied to a string or array variable or literal value.
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index bd1368383..444552718 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -23,11 +23,10 @@ Future Things and Ideas
 ^^^^^^^^^^^^^^^^^^^^^^^
 Compiler:
 
+- pipe operator: allow non-unary function calls in the pipe that specify the other argument(s) in the calls.
 - writeAssembly(): make it possible to actually get rid of the VarDecl nodes by fixing the rest of the code mentioned there.
 - make everything an expression? (get rid of Statements. Statements are expressions with void return types?).
 - allow "xxx" * constexpr  (where constexpr is not a number literal), now gives expression error not same type
-- for the pipe operator: recognise a placeholder (``?`` or ``%`` or ``_``) in a non-unary function call to allow non-unary functions in the chain; ``4 |> mkword(?, $44) |> print_uw``
-  OR: change pipe syntax and require function call, but always have implicit first argument added.
 - for the pipe operator: make it 100% syntactic sugar so there's no need for asm codegen like translatePipeExpression
 - make it possible to inline non-asmsub routines that just contain a single statement (return, functioncall, assignment)
   but this requires all identifiers in the inlined expression to be changed to fully scoped names.
diff --git a/examples/test.p8 b/examples/test.p8
index 636f20447..c074a7e1b 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,20 +1,27 @@
 %import textio
+%import floats
+%import test_stack
+%zeropage basicsafe
 
 main {
     sub start() {
-        ubyte xx = 30
-        ubyte cc
-
-        cc=0
-        cc = 30 |> sin8u |> cos8u |> cc
-        txt.print_ub(cc)
-        txt.nl()
-        cc=0
-        cc = xx |> sin8u |> cos8u |> cc
-        txt.print_ub(cc)
-        txt.nl()
-
-        repeat {
-        }
+    get_player(1)
+        |> determine_score()
+        |> add_bonus()
+        |> txt.print_uw()
     }
+
+    sub get_player(ubyte xx) -> ubyte {
+        return xx+33
+    }
+
+    sub determine_score() -> ubyte {
+        return 33
+    }
+
+    sub add_bonus(ubyte qq) {
+        qq++
+    }
+
+
 }