void syntax check, fixes #135

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

@@ -570,6 +570,13 @@ internal class AstChecker(private val program: Program,
             checkType(assignment.target, assignment.value, assignment.isAugmentable)
         }
 
+        if(assignment.target.void && assignment.target.multi?.isNotEmpty()!=true) {
+            if(assignment.value is IFunctionCall)
+                errors.err("cannot assign to 'void', perhaps a void function call was intended", assignment.position)
+            else
+                errors.err("cannot assign to 'void'", assignment.position)
+            return
+        }
 
         val fcall = assignment.value as? IFunctionCall
         val fcallTarget = fcall?.target?.targetSubroutine(program)

compiler/test/ast/TestVariousCompilerAst.kt

@@ -4,6 +4,7 @@ import io.kotest.core.spec.style.FunSpec
 import io.kotest.matchers.shouldBe
 import io.kotest.matchers.shouldNotBe
 import io.kotest.matchers.string.shouldContain
+import io.kotest.matchers.string.shouldEndWith
 import io.kotest.matchers.types.instanceOf
 import prog8.ast.IFunctionCall
 import prog8.ast.expressions.*
@@ -612,5 +613,30 @@ main {
 }"""
         compileText(Cx16Target(), false, src) shouldNotBe null
     }
+
+    test("void assignment is invalid") {
+        val src="""
+main {
+    romsub $2000 = multi() -> ubyte @A, ubyte @Y
+    romsub $3000 = single() -> ubyte @A
+    
+    sub start() {
+        void, void = multi()        ; ok
+        cx16.r0L, void = multi()    ; ok
+        void, cx16.r0L = multi()    ; ok
+        void multi()                ; ok
+        void single()               ; ok
+        void = 3333                 ; fail!
+        void = single()             ; fail!
+        void = multi()              ; fail!
+    }
+}"""
+        val errors = ErrorReporterForTests()
+        compileText(C64Target(), optimize=false, src, writeAssembly=true, errors = errors) shouldBe null
+        errors.errors.size shouldBe 3
+        errors.errors[0] shouldEndWith "cannot assign to 'void'"
+        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"
+    }
 })
 

examples/test.p8

@@ -1,10 +1,7 @@
-%import textio
 %zeropage basicsafe
 
 main {
     sub start() {
-    uword workFunc=$2000
-
-    void = call(workFunc)
+        void = call($2000)
     }
 }