antlr grammar now understands underscores in identifier names

compiler/src/prog8/compiler/astprocessing/AstChecker.kt

@@ -52,6 +52,8 @@ internal class AstChecker(private val program: Program,
 
     override fun visit(module: Module) {
         super.visit(module)
+        if(module.name.startsWith('_'))
+            errors.err("module names cannot start with an underscore", module.position)
         val directives = module.statements.filterIsInstance<Directive>().groupBy { it.directive }
         directives.filter { it.value.size > 1 }.forEach{ entry ->
             when(entry.key) {
@@ -62,6 +64,10 @@ internal class AstChecker(private val program: Program,
     }
 
     override fun visit(identifier: IdentifierReference) {
+        if(identifier.nameInSource.any { it.startsWith('_') }) {
+            errors.err("identifiers cannot start with an underscore", identifier.position)
+        }
+
         checkLongType(identifier)
         val stmt = identifier.targetStatement(program)
         if(stmt==null)
@@ -266,6 +272,9 @@ internal class AstChecker(private val program: Program,
     }
 
     override fun visit(block: Block) {
+        if(block.name.startsWith('_'))
+            errors.err("block names cannot start with an underscore", block.position)
+
         val addr = block.address
         if(addr!=null && addr>65535u) {
             errors.err("block memory address must be valid integer 0..\$ffff", block.position)
@@ -295,6 +304,9 @@ internal class AstChecker(private val program: Program,
     }
 
     override fun visit(label: Label) {
+        if(label.name.startsWith('_'))
+            errors.err("labels cannot start with an underscore", label.position)
+
         // scope check
         if(label.parent !is Block && label.parent !is Subroutine && label.parent !is AnonymousScope) {
             errors.err("Labels can only be defined in the scope of a block, a loop body, or within another subroutine", label.position)
@@ -336,6 +348,9 @@ internal class AstChecker(private val program: Program,
     override fun visit(subroutine: Subroutine) {
         fun err(msg: String) = errors.err(msg, subroutine.position)
 
+        if(subroutine.name.startsWith('_'))
+            errors.err("subroutine names cannot start with an underscore", subroutine.position)
+
         if(subroutine.name in BuiltinFunctions)
             err("cannot redefine a built-in function")
 
@@ -474,6 +489,9 @@ internal class AstChecker(private val program: Program,
         // Non-string and non-ubytearray Pass-by-reference datatypes can not occur as parameters to a subroutine directly
         // Instead, their reference (address) should be passed (as an UWORD).
         for(p in subroutine.parameters) {
+            if(p.name.startsWith('_'))
+                errors.err("parameter names cannot start with an underscore", p.position)
+
             if(p.type in PassByReferenceDatatypes && p.type !in listOf(DataType.STR, DataType.ARRAY_UB)) {
                 errors.err("this pass-by-reference type can't be used as a parameter type. Instead, use an uword to receive the address, or access the variable from the outer scope directly.", p.position)
             }

compilerAst/src/prog8/ast/antlr/Antlr2Kotlin.kt

@@ -246,7 +246,8 @@ private fun Asmsub_paramsContext.toAst(): List<AsmSubroutineParameter>
     val identifiers = vardecl.identifier()
     if(identifiers.size>1)
         throw SyntaxError("parameter name must be singular", identifiers[0].toPosition())
-    AsmSubroutineParameter(identifiers[0].NAME().text, datatype, registerorpair, statusregister, toPosition())
+    val identifiername = identifiers[0].NAME() ?: identifiers[0].UNDERSCORENAME() ?: identifiers[0].UNDERSCOREPLACEHOLDER()
+    AsmSubroutineParameter(identifiername.text, datatype, registerorpair, statusregister, toPosition())
 }
 
 private fun Functioncall_stmtContext.toAst(): Statement {
@@ -316,7 +317,8 @@ private fun Sub_paramsContext.toAst(): List<SubroutineParameter> =
             val identifiers = it.identifier()
             if(identifiers.size>1)
                 throw SyntaxError("parameter name must be singular", identifiers[0].toPosition())
-            SubroutineParameter(identifiers[0].NAME().text, datatype, it.toPosition())
+            val identifiername = identifiers[0].NAME() ?: identifiers[0].UNDERSCORENAME() ?: identifiers[0].UNDERSCOREPLACEHOLDER()
+            SubroutineParameter(identifiername.text, datatype, it.toPosition())
         }
 
 private fun Assign_targetContext.toAst() : AssignTarget {
@@ -556,8 +558,9 @@ private fun StringliteralContext.toAst(): StringLiteral {
 
 private fun Expression_listContext.toAst() = expression().map{ it.toAst() }
 
-private fun Scoped_identifierContext.toAst() : IdentifierReference =
-        IdentifierReference(NAME().map { it.text }, toPosition())
+private fun Scoped_identifierContext.toAst() : IdentifierReference {
+    return IdentifierReference(identifier().map { it.text }, toPosition())
+}
 
 private fun FloatliteralContext.toAst() = text.replace("_","").toDouble()
 
@@ -669,7 +672,8 @@ private fun VardeclContext.toAst(type: VarDeclType, value: Expression?): VarDecl
         else -> ZeropageWish.DONTCARE
     }
     val identifiers = identifier()
-    val name = if(identifiers.size==1) identifiers[0].NAME().text else "<multiple>"
+    val identifiername = identifiers[0].NAME() ?: identifiers[0].UNDERSCORENAME() ?: identifiers[0].UNDERSCOREPLACEHOLDER()
+    val name = if(identifiers.size==1) identifiername.text else "<multiple>"
     val isArray = ARRAYSIG() != null || arrayindex() != null
     val split = options.SPLIT().isNotEmpty()
     val origDt = datatype()?.toAst() ?: DataType.UNDEFINED
@@ -690,7 +694,10 @@ private fun VardeclContext.toAst(type: VarDeclType, value: Expression?): VarDecl
             zp,
             arrayindex()?.toAst(),
             name,
-            if(identifiers.size==1) emptyList() else identifiers.map { it.NAME().text },
+            if(identifiers.size==1) emptyList() else identifiers.map {
+                val idname = it.NAME() ?: it.UNDERSCORENAME() ?: it.UNDERSCOREPLACEHOLDER()
+                idname.text
+            },
             value,
             options.SHARED().isNotEmpty(),
             split,

compilerAst/src/prog8/ast/expressions/AstExpressions.kt

@@ -906,12 +906,12 @@ class ArrayLiteral(val type: InferredTypes.InferredType,     // inferred because
             else if(elementType in WordDatatypes && value.all { it is NumericLiteral || it is AddressOf || it is IdentifierReference}) {
                 val castArray = value.map {
                     when(it) {
-                        is AddressOf -> it as Expression
-                        is IdentifierReference -> it as Expression
+                        is AddressOf -> it
+                        is IdentifierReference -> it
                         is NumericLiteral -> {
                             val numcast = it.cast(elementType, true)
                             if(numcast.isValid)
-                                numcast.valueOrZero() as Expression
+                                numcast.valueOrZero()
                             else
                                 return null     // abort
                         }

docs/source/todo.rst

@@ -2,6 +2,7 @@ TODO
 ====
 
 try to replace the variable number of assignment targets by allowing placeholder '_' target
+or try to do this with 'void' instead, is more prog8-like?
 
 
 check souce code of examples and library, for void calls that could now be turned into multi-assign calls.

parser/antlr/Prog8ANTLR.g4

@@ -25,6 +25,8 @@ WS :  [ \t] -> skip ;
 // WS2 : '\\' EOL -> skip;
 VOID: 'void';
 NAME :  [\p{Letter}][\p{Letter}\p{Mark}\p{Digit}_]* ;           // match unicode properties
+UNDERSCORENAME :  '_' NAME ;           // match unicode properties
+UNDERSCOREPLACEHOLDER:  '_' ;
 DEC_INTEGER :  DEC_DIGIT (DEC_DIGIT | '_')* ;
 HEX_INTEGER :  '$' HEX_DIGIT (HEX_DIGIT | '_')* ;
 BIN_INTEGER :  '%' BIN_DIGIT (BIN_DIGIT | '_')* ;
@@ -220,9 +222,9 @@ breakstmt : 'break';
 
 continuestmt: 'continue';
 
-identifier :  NAME ;
+identifier :  NAME | UNDERSCORENAME | UNDERSCOREPLACEHOLDER;
 
-scoped_identifier :  NAME ('.' NAME)* ;
+scoped_identifier :  identifier ('.' identifier)* ;
 
 integerliteral :  intpart=(DEC_INTEGER | HEX_INTEGER | BIN_INTEGER) ;