fix syntax error check for missing return statement

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

@@ -322,7 +322,7 @@ internal class AstChecker(private val program: Program,
         checkLongType(numLiteral)
     }
 
-    private fun hasReturnOrJumpOrRts(scope: IStatementContainer): Boolean {
+    private fun hasReturnOrExternalJumpOrRts(scope: IStatementContainer): Boolean {
         class Searcher: IAstVisitor
         {
             var count=0
@@ -331,7 +331,14 @@ internal class AstChecker(private val program: Program,
                 count++
             }
             override fun visit(jump: Jump) {
-                count++
+                val jumpTarget = jump.identifier?.targetStatement(program)
+                if(jumpTarget!=null) {
+                    val sub = jump.definingSubroutine
+                    val targetSub = if(jumpTarget is Subroutine) jumpTarget else jumpTarget.definingSubroutine
+                    if(sub !== targetSub)
+                        count++
+                }
+                else count++
             }
 
             override fun visit(inlineAssembly: InlineAssembly) {
@@ -374,11 +381,11 @@ internal class AstChecker(private val program: Program,
 
         // subroutine must contain at least one 'return' or 'goto'
         // (or if it has an asm block, that must contain a 'rts' or 'jmp' or 'bra')
-        if(!hasReturnOrJumpOrRts(subroutine)) {
+        if(!hasReturnOrExternalJumpOrRts(subroutine)) {
             if (subroutine.returntypes.isNotEmpty()) {
                 // for asm subroutines with an address, no statement check is possible.
                 if (subroutine.asmAddress == null && !subroutine.inline)
-                    err("non-inline subroutine has result value(s) and thus must have at least one 'return' or 'goto' in it (or the assembler equivalent in case of %asm)")
+                    err("non-inline subroutine has result value(s) and thus must have at least one 'return' or external 'goto' in it (or the assembler equivalent in case of %asm)")
             }
         }
 

compiler/test/ast/TestVariousCompilerAst.kt

@@ -638,5 +638,53 @@ main {
         errors.errors[1] shouldEndWith "cannot assign to 'void', perhaps a void function call was intended"
         errors.errors[2] shouldEndWith "cannot assign to 'void', perhaps a void function call was intended"
     }
+
+    test("missing return value is a syntax error") {
+        val src="""
+main {
+    sub start() {
+        cx16.r0 = runit1()
+        cx16.r1 = runit2()
+    }
+
+    sub runit1() -> uword {
+        repeat {
+            cx16.r0++
+            goto runit1
+        }
+    }
+
+    sub runit2() -> uword {
+        cx16.r0++
+    }
+}"""
+        val errors = ErrorReporterForTests()
+        compileText(C64Target(), optimize=false, src, writeAssembly=false, errors = errors) shouldBe null
+        errors.errors.size shouldBe 2
+        errors.errors[0] shouldContain "has result value"
+        errors.errors[1] shouldContain "has result value"
+    }
+
+    test("missing return value is not a syntax error if there's an external goto") {
+        val src="""
+main {
+    sub start() {
+        cx16.r0 = runit1()
+        runit2()
+    }
+
+    sub runit1() -> uword {
+        repeat {
+            cx16.r0++
+            goto runit2
+        }
+    }
+
+    sub runit2() {
+        cx16.r0++
+    }
+}"""
+        compileText(C64Target(), optimize=false, src, writeAssembly=false) shouldNotBe null
+    }
 })
 

compilerAst/src/prog8/ast/AstToSourceTextConverter.kt

@@ -254,7 +254,6 @@ class AstToSourceTextConverter(val output: (text: String) -> Unit, val program:
         output("goto ")
         when {
             jump.address!=null -> output(jump.address!!.toHex())
-            jump.generatedLabel!=null -> output(jump.generatedLabel)
             jump.identifier!=null -> jump.identifier.accept(this)
         }
     }

compilerAst/src/prog8/ast/Program.kt

@@ -158,6 +158,6 @@ class Program(val name: String,
 
     fun jumpLabel(label: Label): Jump {
         val ident = IdentifierReference(listOf(label.name), label.position)
-        return Jump(null, ident, null, label.position)
+        return Jump(null, ident, label.position)
     }
 }

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

@@ -284,7 +284,7 @@ private fun ReturnstmtContext.toAst() : Return {
 private fun UnconditionaljumpContext.toAst(): Jump {
     val address = integerliteral()?.toAst()?.number?.toUInt()
     val identifier = scoped_identifier()?.toAst()
-    return Jump(address, identifier, null, toPosition())
+    return Jump(address, identifier, toPosition())
 }
 
 private fun LabeldefContext.toAst(): Statement =

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

@@ -642,7 +642,6 @@ data class AssignTarget(var identifier: IdentifierReference?,
 
 class Jump(var address: UInt?,
            val identifier: IdentifierReference?,
-           val generatedLabel: String?,             // can be used in code generation scenarios
            override val position: Position) : Statement() {
     override lateinit var parent: Node
 
@@ -658,13 +657,13 @@ class Jump(var address: UInt?,
         else
             throw FatalAstException("can't replace $node")
     }
-    override fun copy() = Jump(address, identifier?.copy(), generatedLabel, position)
+    override fun copy() = Jump(address, identifier?.copy(), position)
     override fun accept(visitor: IAstVisitor) = visitor.visit(this)
     override fun accept(visitor: AstWalker, parent: Node) = visitor.visit(this, parent)
     override fun referencesIdentifier(nameInSource: List<String>): Boolean = identifier?.referencesIdentifier(nameInSource)==true
 
     override fun toString() =
-        "Jump(addr: $address, identifier: $identifier, label: $generatedLabel;  pos=$position)"
+        "Jump(addr: $address, identifier: $identifier, pos=$position)"
 }
 
 class FunctionCallStatement(override var target: IdentifierReference,

docs/source/todo.rst

@@ -1,8 +1,6 @@
 TODO
 ====
 
-Textelite main.start() -> no error when a return value is added but no return statement
-
 Can we move the asm init code that is injected into the start() subroutine, to init_system_phase2 instead?
 
 Doc improvements: some short overview for people coming from other programming languages like C: