From 7afc96112b56499c92dcaeace0750583c947037a Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sun, 23 Jan 2022 02:23:30 +0100
Subject: [PATCH] now correctly requires using & (address-of) when assigning
 the address of a label or subroutine, used to generate invalid code when it
 was omitted

---
 .../compiler/astprocessing/AstChecker.kt      |  2 +-
 compiler/test/TestAstChecks.kt                | 26 +++++++++++++++++++
 .../prog8/ast/expressions/AstExpressions.kt   |  1 -
 docs/source/todo.rst                          |  2 +-
 examples/test.p8                              | 12 +++++++--
 5 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/compiler/src/prog8/compiler/astprocessing/AstChecker.kt b/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
index ae1ede7d1..2db3c8c0d 100644
--- a/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
+++ b/compiler/src/prog8/compiler/astprocessing/AstChecker.kt
@@ -497,7 +497,7 @@ internal class AstChecker(private val program: Program,
                     val sourceDatatype = assignment.value.inferType(program)
                     if (sourceDatatype.isUnknown) {
                         if (assignment.value !is FunctionCallExpression)
-                            errors.err("assignment value is invalid or has no proper datatype", assignment.value.position)
+                            errors.err("assignment value is invalid or has no proper datatype, maybe forgot '&' (address-of)", assignment.value.position)
                     } else {
                         checkAssignmentCompatible(targetDatatype.getOr(DataType.BYTE),
                                 sourceDatatype.getOr(DataType.BYTE), assignment.value)
diff --git a/compiler/test/TestAstChecks.kt b/compiler/test/TestAstChecks.kt
index dad3afbc0..8c8e9532f 100644
--- a/compiler/test/TestAstChecks.kt
+++ b/compiler/test/TestAstChecks.kt
@@ -5,6 +5,7 @@ import io.kotest.matchers.shouldBe
 import io.kotest.matchers.string.shouldContain
 import prog8.codegen.target.C64Target
 import prog8tests.helpers.ErrorReporterForTests
+import prog8tests.helpers.assertFailure
 import prog8tests.helpers.assertSuccess
 import prog8tests.helpers.compileText
 
@@ -30,4 +31,29 @@ class TestAstChecks: FunSpec({
         errors.warnings[0] shouldContain "converted to float"
         errors.warnings[1] shouldContain "converted to float"
     }
+
+    test("can't assign label or subroutine without using address-of") {
+        val text = """
+            main {
+                sub start() {
+            
+            label:
+                    uword @shared addr
+                    addr = label
+                    addr = thing
+                    addr = &label
+                    addr = &thing
+                }
+            
+                sub thing() {
+                }
+            }
+            """
+        val errors = ErrorReporterForTests()
+        compileText(C64Target, true, text, writeAssembly = true, errors=errors).assertFailure()
+        errors.errors.size shouldBe 2
+        errors.warnings.size shouldBe 0
+        errors.errors[0] shouldContain ":7:28) assignment value is invalid"
+        errors.errors[1] shouldContain ":8:28) assignment value is invalid"
+    }
 })
diff --git a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
index 497c55ef2..8cf270e14 100644
--- a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
+++ b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
@@ -896,7 +896,6 @@ data class IdentifierReference(val nameInSource: List<String>, override val posi
     override fun inferType(program: Program): InferredTypes.InferredType {
         return when (val targetStmt = targetStatement(program)) {
             is VarDecl -> InferredTypes.knownFor(targetStmt.datatype)
-            is Label -> InferredTypes.InferredType.known(DataType.UWORD)
             else -> InferredTypes.InferredType.unknown()
         }
     }
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index c70b607b1..53c792054 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,7 +3,6 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
-- Fix:  uword addr = label    ; addr will be 0!  required to use &label!
 - Fix compiler stack overflow crash:
     sub sprite_y_for_row(ubyte row) -> word {
         return (8-row as byte)
@@ -44,6 +43,7 @@ Blocked by an official Commander-x16 r39 release
 
 Future Things and Ideas
 ^^^^^^^^^^^^^^^^^^^^^^^
+- Fix: don't report as recursion if code assign address of its own subroutine to something, rather than calling it
 - allow "xxx" * constexpr  (where constexpr is not a number literal, now gives expression error not same type)
 - can we promise a left-to-right function call argument evaluation? without sacrificing performance
 - unify FunctioncallExpression + FunctioncallStatement and PipeExpression + Pipe statement, may require moving Expression/Statement into interfaces instead of abstract base classes
diff --git a/examples/test.p8 b/examples/test.p8
index cb9f40973..22fe9c3d9 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -3,7 +3,15 @@
 
 main {
     sub start() {
-        uword @shared qq = $2ff33
-        cx16.r0 = $1fc0f
+
+label:
+        uword @shared addr
+        addr = label
+        addr = thing
+        addr = &label
+        addr = &thing
+    }
+
+    sub thing() {
     }
 }