new ast: regular subroutine has just 0 or 1 return type

codeAst/src/prog8/code/ast/AstStatements.kt

@@ -21,7 +21,7 @@ class PtAsmSub(
 class PtSub(
     name: String,
     val parameters: List<PtSubroutineParameter>,
-    val returntypes: List<DataType>,
+    val returntype: DataType?,
     val inline: Boolean,
     position: Position
 ) : PtNamedNode(name, position) {

compiler/src/prog8/compiler/IntermediateAstMaker.kt

@@ -284,7 +284,7 @@ class IntermediateAstMaker(val srcProgram: Program) {
     private fun transformSub(srcSub: Subroutine): PtSub {
         val sub = PtSub(srcSub.name,
             srcSub.parameters.map { PtSubroutineParameter(it.name, it.type, it.position) },
-            srcSub.returntypes,
+            srcSub.returntypes.singleOrNull(),
             srcSub.inline,
             srcSub.position)
 

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

@@ -275,20 +275,15 @@ private fun Prog8ANTLRParser.LabeldefContext.toAst(): Statement =
 private fun Prog8ANTLRParser.SubroutineContext.toAst() : Subroutine {
     // non-asm subroutine
     val inline = inline()!=null
-    val returntypes = sub_return_part()?.toAst() ?: emptyList()
+    val returntype = sub_return_part()?.datatype()?.toAst()
     return Subroutine(identifier().text,
             sub_params()?.toAst()?.toMutableList() ?: mutableListOf(),
-            returntypes,
+            if(returntype==null) emptyList() else listOf(returntype),
             statement_block()?.toAst() ?: mutableListOf(),
             inline,
             toPosition())
 }
 
-private fun Prog8ANTLRParser.Sub_return_partContext.toAst(): List<DataType> {
-    val returns = sub_returns() ?: return emptyList()
-    return returns.datatype().map { it.toAst() }
-}
-
 private fun Prog8ANTLRParser.Sub_paramsContext.toAst(): List<SubroutineParameter> =
         vardecl().map {
             var datatype = it.datatype()?.toAst() ?: DataType.UNDEFINED

examples/test.p8

@@ -31,6 +31,9 @@ main {
         ; test_stack.test()
     }
 
+    sub derp() -> ubyte, ubyte {
+        return 0, 1
+    }
 
     sub find_next_prime() -> ubyte {
 

parser/antlr/Prog8ANTLR.g4

@@ -245,7 +245,7 @@ subroutine :
 	inline? 'sub' identifier '(' sub_params? ')' sub_return_part?  (statement_block EOL)
 	;
 
-sub_return_part : '->' sub_returns  ;
+sub_return_part : '->' datatype  ;
 
 statement_block :
 	'{' EOL
@@ -256,8 +256,6 @@ statement_block :
 
 sub_params :  vardecl (',' EOL? vardecl)* ;
 
-sub_returns :  datatype (',' EOL? datatype)*  ;
-
 asmsubroutine :
     inline? 'asmsub' asmsub_decl  statement_block
     ;