return statement only has one single possible value

astvm can now more or less run all examples

clean.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env sh
 
 rm *.jar *.asm *.prg *.vm.txt *.vice-mon-list
-rm -r build
+rm -rf build out
 

compiler/res/version.txt

@@ -1 +1 @@
-1.10-dev
+1.10

compiler/src/prog8/ast/antlr/Antr2Kotlin.kt

@@ -246,8 +246,7 @@ private fun prog8Parser.InlineasmContext.toAst() =
 
 
 private fun prog8Parser.ReturnstmtContext.toAst() : Return {
-    val values = expression_list()
-    return Return(values?.toAst() ?: emptyList(), toPosition())
+    return Return(expression()?.toAst(), toPosition())
 }
 
 private fun prog8Parser.UnconditionaljumpContext.toAst(): Jump {

compiler/src/prog8/ast/processing/AstChecker.kt

@@ -90,20 +90,20 @@ internal class AstChecker(private val program: Program,
 
     override fun visit(returnStmt: Return): IStatement {
         val expectedReturnValues = returnStmt.definingSubroutine()?.returntypes ?: emptyList()
-        if(expectedReturnValues.size != returnStmt.values.size) {
-            // if the return value is a function call, check the result of that call instead
-            if(returnStmt.values.size==1 && returnStmt.values[0] is FunctionCall) {
-                val dt = (returnStmt.values[0] as FunctionCall).inferType(program)
-                if(dt!=null && expectedReturnValues.isEmpty())
-                    checkResult.add(SyntaxError("invalid number of return values", returnStmt.position))
-            } else
-                checkResult.add(SyntaxError("invalid number of return values", returnStmt.position))
+        if(expectedReturnValues.size>1) {
+            throw AstException("cannot use a return with one value in a subroutine that has multiple return values: $returnStmt")
         }
 
-        for (rv in expectedReturnValues.withIndex().zip(returnStmt.values)) {
-            val valueDt=rv.second.inferType(program)
-            if(rv.first.value!=valueDt)
-                checkResult.add(ExpressionError("type $valueDt of return value #${rv.first.index + 1} doesn't match subroutine return type ${rv.first.value}", rv.second.position))
+        if(expectedReturnValues.isEmpty() && returnStmt.value!=null) {
+            checkResult.add(SyntaxError("invalid number of return values", returnStmt.position))
+        }
+        if(expectedReturnValues.isNotEmpty() && returnStmt.value==null) {
+            checkResult.add(SyntaxError("invalid number of return values", returnStmt.position))
+        }
+        if(expectedReturnValues.size==1 && returnStmt.value!=null) {
+            val valueDt = returnStmt.value!!.inferType(program)
+            if(expectedReturnValues[0]!=valueDt)
+                checkResult.add(ExpressionError("type $valueDt of return value doesn't match subroutine's return type", returnStmt.value!!.position))
         }
         return super.visit(returnStmt)
     }

compiler/src/prog8/ast/processing/AstIdentifiersChecker.kt

@@ -168,25 +168,23 @@ internal class AstIdentifiersChecker(private val namespace: INameScope) : IAstMo
     }
 
     override fun visit(returnStmt: Return): IStatement {
-        if(returnStmt.values.isNotEmpty()) {
+        if(returnStmt.value!=null) {
             // possibly adjust any literal values returned, into the desired returning data type
             val subroutine = returnStmt.definingSubroutine()!!
-            if(subroutine.returntypes.size!=returnStmt.values.size)
+            if(subroutine.returntypes.size!=1)
                 return returnStmt  // mismatch in number of return values, error will be printed later.
-            val newValues = mutableListOf<IExpression>()
-            for(returnvalue in returnStmt.values.zip(subroutine.returntypes)) {
-                val lval = returnvalue.first as? LiteralValue
-                if(lval!=null) {
-                    val adjusted = lval.cast(returnvalue.second)
-                    if(adjusted!=null && adjusted !== lval)
-                        newValues.add(adjusted)
-                    else
-                        newValues.add(lval)
-                }
+            val newValue: IExpression
+            val lval = returnStmt.value as? LiteralValue
+            if(lval!=null) {
+                val adjusted = lval.cast(subroutine.returntypes.single())
+                if(adjusted!=null && adjusted !== lval)
+                    newValue = adjusted
                 else
-                    newValues.add(returnvalue.first)
-            }
-            returnStmt.values = newValues
+                    newValue = lval
+            } else
+                newValue = returnStmt.value!!
+
+            returnStmt.value = newValue
         }
         return super.visit(returnStmt)
     }

compiler/src/prog8/ast/processing/IAstModifyingVisitor.kt

@@ -149,7 +149,7 @@ interface IAstModifyingVisitor {
     }
 
     fun visit(returnStmt: Return): IStatement {
-        returnStmt.values = returnStmt.values.map { it.accept(this) }
+        returnStmt.value = returnStmt.value?.accept(this)
         return returnStmt
     }
 

compiler/src/prog8/ast/processing/IAstVisitor.kt

@@ -111,7 +111,7 @@ interface IAstVisitor {
     }
 
     fun visit(returnStmt: Return) {
-        returnStmt.values.forEach { it.accept(this) }
+        returnStmt.value?.accept(this)
     }
 
     fun visit(arrayIndexedExpression: ArrayIndexedExpression) {

compiler/src/prog8/ast/processing/StatementReorderer.kt

@@ -89,7 +89,7 @@ internal class StatementReorderer(private val program: Program): IAstModifyingVi
                         && stmtBeforeFirstSub !is Jump
                         && stmtBeforeFirstSub !is Subroutine
                         && stmtBeforeFirstSub !is BuiltinFunctionStatementPlaceholder) {
-                    val ret = Return(emptyList(), stmtBeforeFirstSub.position)
+                    val ret = Return(null, stmtBeforeFirstSub.position)
                     ret.linkParents(block)
                     block.statements.add(block.statements.size - numSubroutinesAtEnd, ret)
                 }
@@ -137,7 +137,7 @@ internal class StatementReorderer(private val program: Program): IAstModifyingVi
             // and if an assembly block doesn't contain a rts/rti
             if(subroutine.asmAddress==null && subroutine.amountOfRtsInAsm()==0) {
                 if (subroutine.statements.lastOrNull {it !is VarDecl } !is Return) {
-                    val returnStmt = Return(emptyList(), subroutine.position)
+                    val returnStmt = Return(null, subroutine.position)
                     returnStmt.linkParents(subroutine)
                     subroutine.statements.add(returnStmt)
                 }

compiler/src/prog8/ast/statements/AstStatements.kt

@@ -84,24 +84,24 @@ data class Label(val name: String, override val position: Position) : IStatement
     val scopedname: String by lazy { makeScopedName(name) }
 }
 
-open class Return(var values: List<IExpression>, override val position: Position) : IStatement {
+open class Return(var value: IExpression?, override val position: Position) : IStatement {
     override lateinit var parent: Node
-    override val expensiveToInline = values.any { it !is LiteralValue }
+    override val expensiveToInline = value!=null && value !is LiteralValue
 
     override fun linkParents(parent: Node) {
         this.parent = parent
-        values.forEach {it.linkParents(this)}
+        value?.linkParents(this)
     }
 
     override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
     override fun accept(visitor: IAstVisitor) = visitor.visit(this)
 
     override fun toString(): String {
-        return "Return(values: $values, pos=$position)"
+        return "Return($value, pos=$position)"
     }
 }
 
-class ReturnFromIrq(override val position: Position) : Return(emptyList(), position) {
+class ReturnFromIrq(override val position: Position) : Return(null, position) {
     override fun accept(visitor: IAstModifyingVisitor) = visitor.visit(this)
     override fun accept(visitor: IAstVisitor) = visitor.visit(this)
 

compiler/src/prog8/compiler/AstToSourceCode.kt

@@ -327,11 +327,7 @@ class AstToSourceCode(val output: (text: String) -> Unit): IAstVisitor {
 
     override fun visit(returnStmt: Return) {
         output("return ")
-        for(v in returnStmt.values) {
-            v.accept(this)
-            if(v!==returnStmt.values.last())
-                output(", ")
-        }
+        returnStmt.value?.accept(this)
     }
 
     override fun visit(arrayIndexedExpression: ArrayIndexedExpression) {

compiler/src/prog8/compiler/Compiler.kt

@@ -1517,9 +1517,8 @@ internal class Compiler(private val program: Program) {
 
     private fun translate(stmt: Return) {
         // put the return values on the stack, in reversed order. The caller will accept them.
-        for(value in stmt.values.reversed()) {
-            translate(value)
-        }
+        if(stmt.value!=null)
+            translate(stmt.value!!)
         prog.line(stmt.position)
         prog.instr(Opcode.RETURN)
     }

compiler/src/prog8/compiler/Main.kt

@@ -88,7 +88,7 @@ fun compileProgram(filepath: Path,
             programAst.checkValid(compilerOptions)          // check if final tree is valid
             programAst.checkRecursion()         // check if there are recursive subroutine calls
 
-            printAst(programAst)
+            // printAst(programAst)
             // namespace.debugPrint()
 
             if(generateVmCode) {

compiler/src/prog8/optimizer/StatementOptimizer.kt

@@ -79,7 +79,6 @@ internal class StatementOptimizer(private val program: Program, private val opti
             }
             val returns = inlined.statements.withIndex().filter { iv -> iv.value is Return }.map { iv -> Pair(iv.index, iv.value as Return)}
             for(returnIdx in returns) {
-                assert(returnIdx.second.values.isEmpty())
                 val jump = Jump(null, IdentifierReference(listOf(endlabel.name), returnIdx.second.position), null, returnIdx.second.position)
                 inlined.statements[returnIdx.first] = jump
                 endLabelUsed = true
@@ -299,8 +298,8 @@ internal class StatementOptimizer(private val program: Program, private val opti
                 optimizationsDone++
                 return FunctionCall(first.identifier, functionCall.arglist, functionCall.position)
             }
-            if(first is Return && first.values.size==1) {
-                val constval = first.values[0].constValue(program)
+            if(first is Return && first.value!=null) {
+                val constval = first.value?.constValue(program)
                 if(constval!=null)
                     return constval
             }

compiler/src/prog8/vm/astvm/AstVm.kt

@@ -261,11 +261,11 @@ class AstVm(val program: Program) {
 
     class LoopControlBreak : Exception()
     class LoopControlContinue : Exception()
-    class LoopControlReturn(val returnvalues: List<RuntimeValue>) : Exception()
+    class LoopControlReturn(val returnvalue: RuntimeValue?) : Exception()
     class LoopControlJump(val identifier: IdentifierReference?, val address: Int?, val generatedLabel: String?) : Exception()
 
 
-    internal fun executeSubroutine(sub: Subroutine, arguments: List<RuntimeValue>, startlabel: Label?=null): List<RuntimeValue> {
+    internal fun executeSubroutine(sub: Subroutine, arguments: List<RuntimeValue>, startlabel: Label?=null): RuntimeValue? {
         if(sub.isAsmSubroutine) {
             return performSyscall(sub, arguments)
         }
@@ -300,7 +300,7 @@ class AstVm(val program: Program) {
                 }
             }
         } catch (r: LoopControlReturn) {
-            return r.returnvalues
+            return r.returnvalue
         }
         throw VmTerminationException("instruction pointer overflow, is a return missing? $sub")
     }
@@ -355,7 +355,14 @@ class AstVm(val program: Program) {
                     }
                 }
             }
-            is Return -> throw LoopControlReturn(stmt.values.map { evaluate(it, evalCtx) })
+            is Return -> {
+                val value =
+                        if(stmt.value==null)
+                            null
+                        else
+                            evaluate(stmt.value!!, evalCtx)
+                throw LoopControlReturn(value)
+            }
             is Continue -> throw LoopControlContinue()
             is Break -> throw LoopControlBreak()
             is Assignment -> {
@@ -430,7 +437,7 @@ class AstVm(val program: Program) {
                 if (sub is Subroutine) {
                     val args = sub.parameters.map { runtimeVariables.get(sub, it.name) }
                     performSyscall(sub, args)
-                    throw LoopControlReturn(emptyList())
+                    throw LoopControlReturn(null)
                 }
                 throw VmExecutionException("can't execute inline assembly in $sub")
             }
@@ -635,8 +642,8 @@ class AstVm(val program: Program) {
 
     private fun evaluate(args: List<IExpression>) = args.map { evaluate(it, evalCtx) }
 
-    private fun performSyscall(sub: Subroutine, args: List<RuntimeValue>): List<RuntimeValue> {
-        val result = mutableListOf<RuntimeValue>()
+    private fun performSyscall(sub: Subroutine, args: List<RuntimeValue>): RuntimeValue? {
+        var result: RuntimeValue? = null
         when (sub.scopedname) {
             "c64scr.print" -> {
                 // if the argument is an UWORD, consider it to be the "address" of the string (=heapId)
@@ -720,7 +727,7 @@ class AstVm(val program: Program) {
                 val origStr = program.heap.get(heapId).str!!
                 val paddedStr=inputStr.padEnd(origStr.length+1, '\u0000').substring(0, origStr.length)
                 program.heap.update(heapId, paddedStr)
-                result.add(RuntimeValue(DataType.UBYTE, paddedStr.indexOf('\u0000')))
+                result = RuntimeValue(DataType.UBYTE, paddedStr.indexOf('\u0000'))
             }
             "c64flt.print_f" -> {
                 dialog.canvas.printText(args[0].floatval.toString(), true)
@@ -736,13 +743,13 @@ class AstVm(val program: Program) {
                     Thread.sleep(10)
                 }
                 val char=dialog.keyboardBuffer.pop()
-                result.add(RuntimeValue(DataType.UBYTE, char.toShort()))
+                result = RuntimeValue(DataType.UBYTE, char.toShort())
             }
             "c64utils.str2uword" -> {
                 val heapId = args[0].wordval!!
                 val argString = program.heap.get(heapId).str!!
                 val numericpart = argString.takeWhile { it.isDigit() }
-                result.add(RuntimeValue(DataType.UWORD, numericpart.toInt() and 65535))
+                result = RuntimeValue(DataType.UWORD, numericpart.toInt() and 65535)
             }
             else -> TODO("syscall  ${sub.scopedname} $sub")
         }

compiler/src/prog8/vm/astvm/Expressions.kt

@@ -16,7 +16,7 @@ import kotlin.math.abs
 class EvalContext(val program: Program, val mem: Memory, val statusflags: StatusFlags,
                   val runtimeVars: RuntimeVariables,
                   val performBuiltinFunction: (String, List<RuntimeValue>, StatusFlags) -> RuntimeValue?,
-                  val executeSubroutine: (sub: Subroutine, args: List<RuntimeValue>, startlabel: Label?) -> List<RuntimeValue>)
+                  val executeSubroutine: (sub: Subroutine, args: List<RuntimeValue>, startlabel: Label?) -> RuntimeValue?)
 
 fun evaluate(expr: IExpression, ctx: EvalContext): RuntimeValue {
     val constval = expr.constValue(ctx.program)
@@ -117,10 +117,9 @@ fun evaluate(expr: IExpression, ctx: EvalContext): RuntimeValue {
             val args = expr.arglist.map { evaluate(it, ctx) }
             return when(sub) {
                 is Subroutine -> {
-                    val results = ctx.executeSubroutine(sub, args, null)
-                    if(results.size!=1)
-                        throw VmExecutionException("expected 1 result from functioncall $expr")
-                    results[0]
+                    val result = ctx.executeSubroutine(sub, args, null)
+                            ?: throw VmExecutionException("expected a result from functioncall $expr")
+                    result
                 }
                 is BuiltinFunctionStatementPlaceholder -> {
                     val result = ctx.performBuiltinFunction(sub.name, args, ctx.statusflags)

examples/numbergame.p8

@@ -32,7 +32,8 @@
             ubyte guess = lsb(c64utils.str2uword(input))
 
             if guess==secretnumber {
-                return ending(true)
+                ending(true)
+                return
             } else {
                 c64scr.print("\n\nThat is too ")
                 if guess<secretnumber
@@ -42,7 +43,8 @@
             }
         }
 
-        return ending(false)        ; @todo error
+        ending(false)
+        return
 
 
         sub ending(ubyte success) {

examples/test.p8

@@ -4,16 +4,18 @@
 ~ main {
 
     sub start() {
-        str  naam = "                               "
 
-        while true {
-            c64scr.print("naam: ")
-            ubyte length = c64scr.input_chars(naam)
-            c64scr.print_ub(length)
-            c64.CHROUT(':')
-            c64scr.print(naam)
-            c64.CHROUT('\n')
-        }
+        foo(42)
+        return
+    }
+
+    sub foo(ubyte arg) -> ubyte {
+        bar(arg)
+        return 33
+    }
+
+    sub bar(ubyte a2) {
+        ;nothing
     }
 
 }

parser/antlr/prog8.g4

@@ -183,7 +183,7 @@ expression_list :
 	expression (',' EOL? expression)*           // you can split the expression list over several lines
 	;
 
-returnstmt : 'return' expression_list? ;
+returnstmt : 'return' expression? ;
 
 breakstmt : 'break';
 

parser/src/prog8/parser/prog8Parser.java

@@ -2265,8 +2265,8 @@ public class prog8Parser extends Parser {
 	}
 
 	public static class ReturnstmtContext extends ParserRuleContext {
-		public Expression_listContext expression_list() {
-			return getRuleContext(Expression_listContext.class,0);
+		public ExpressionContext expression() {
+			return getRuleContext(ExpressionContext.class,0);
 		}
 		public ReturnstmtContext(ParserRuleContext parent, int invokingState) {
 			super(parent, invokingState);
@@ -2288,7 +2288,7 @@ public class prog8Parser extends Parser {
 			case 1:
 				{
 				setState(426);
-				expression_list();
+				expression(0);
 				}
 				break;
 			}
@@ -5147,7 +5147,7 @@ public class prog8Parser extends Parser {
 		"\3\2\2\2\u01a3\u01a4\3\2\2\2\u01a4\u01a5\3\2\2\2\u01a5\u01a7\5&\24\2\u01a6"+
 		"\u01a1\3\2\2\2\u01a7\u01aa\3\2\2\2\u01a8\u01a6\3\2\2\2\u01a8\u01a9\3\2"+
 		"\2\2\u01a9\65\3\2\2\2\u01aa\u01a8\3\2\2\2\u01ab\u01ad\7C\2\2\u01ac\u01ae"+
-		"\5\64\33\2\u01ad\u01ac\3\2\2\2\u01ad\u01ae\3\2\2\2\u01ae\67\3\2\2\2\u01af"+
+		"\5&\24\2\u01ad\u01ac\3\2\2\2\u01ad\u01ae\3\2\2\2\u01ae\67\3\2\2\2\u01af"+
 		"\u01b0\7D\2\2\u01b09\3\2\2\2\u01b1\u01b2\7E\2\2\u01b2;\3\2\2\2\u01b3\u01b4"+
 		"\7t\2\2\u01b4=\3\2\2\2\u01b5\u01ba\7t\2\2\u01b6\u01b7\7F\2\2\u01b7\u01b9"+
 		"\7t\2\2\u01b8\u01b6\3\2\2\2\u01b9\u01bc\3\2\2\2\u01ba\u01b8\3\2\2\2\u01ba"+