Disallow aliasing of @local symbols with a higher visibility in the alias.

releasenotes.md

@@ -8,7 +8,8 @@
 - Add new builtins `$$str_snakecase` `$$str_replace` and `$$str_pascalcase`.
 - `"build-dir"` option now available for `project.json`, added to project. #2323
 - Allow `..` ranges to use "a..a-1" in order to express zero length.
-
+- Disallow aliasing of `@local` symbols with a higher visibility in the alias.
+ 
 ### Fixes
 - Bug in `io::write_using_write_byte`.
 - Bitstruct value cannot be used to index a const array in compile time. #2512
@@ -16,8 +17,8 @@
 - Bitstruct truncated constant error escapes `$defined` #2515.
 - Compiler segfault when accessing member of number cast to bitstruct #2516.
 - Compiler assert when getting a member of a `bitstruct : char @bigendian` #2517.
-- Incorrect visibility on local globals with public aliases. #2519
 - Add ??? and +++= to list-precedence.
+- Fix issues with linking when using symbol aliases. #2519
 
 ### Stdlib changes
 - Sorting functions correctly took slices by value, but also other types by value. Now, only slices are accepted by value, other containers are always by ref.

src/compiler/context.c

@@ -142,6 +142,7 @@ bool context_is_macro(SemaContext *context)
 
 void unit_register_external_symbol(SemaContext *context, Decl *decl)
 {
+	decl = decl_flatten(decl);
 	if (decl->is_external_visible) return;
 	Module *active_module = context->current_macro ? context->original_module : context->compilation_unit->module;
 	if (decl->unit->module == active_module) return;

src/compiler/sema_decls.c

@@ -5302,6 +5302,11 @@ static inline bool sema_analyse_alias(SemaContext *context, Decl *decl, bool *er
 	}
 	decl->type = symbol->type;
 	decl->define_decl.alias = symbol;
+	if (symbol->visibility == VISIBLE_LOCAL && decl->visibility < VISIBLE_LOCAL)
+	{
+		RETURN_SEMA_ERROR(decl, "A local symbol like '%s' may not be aliased to 'private' or 'public' visibility, please change it to at least be '@private'", symbol->name);
+	}
+	// If the symbol is more hidden than the alias, then we must increase the visibility.
 	if (decl_is_externally_visible(decl) && !decl_is_externally_visible(symbol))
 	{
 		symbol->is_external_visible = true;

src/compiler/sema_expr.c

@@ -10614,7 +10614,7 @@ static inline bool sema_expr_analyse_lambda(SemaContext *context, Type *target_t
 		{
 			decl->var.is_read = true;
 		}
-		decl->is_external_visible = true;
+		decl_flatten(decl)->is_external_visible = true;
 		vec_add(unit->module->lambdas_to_evaluate, decl);
 	}
 	else

src/compiler/sema_name_resolution.c

@@ -830,7 +830,7 @@ INLINE bool sema_resolve_symbol_common(SemaContext *context, NameResolve *name_r
 		SEMA_NOTE(found, "'%s' is defined here.", found->name);
 		return false;
 	}
-	unit_register_external_symbol(context, found);
+	if (found->decl_kind != DECL_ALIAS) unit_register_external_symbol(context, found);
 	if (found->unit->module->is_generic)
 	{
 		if (name_resolve->is_parameterized) return true;

test/test_suite/define/alias_visibility.c3t

@@ -1,20 +1,32 @@
 // #target: macos-x64
 module test1;
 alias x = y;
-int y @local = 1;
+int y @private = 1;
+
+module test2;
+int z @private = 1;
 
 module test;
 import test1;
+import test2 @public;
+
+alias z = test2::z;
 
 fn int main(String[] args)
 {
-	return test1::x;
+	return test1::x + z;
 }
 
+
 /* #expect: test1.ll
 
-@test1.y.10 = local_unnamed_addr global i32 1, align 4
+@test1.y = local_unnamed_addr global i32 1, align 4
+
+/* #expect: test2.ll
+
+@test2.z = local_unnamed_addr global i32 1, align 4
 
 // #expect: test.ll
 
-@test1.y.10 = external global i32, align 4
+@test1.y = external global i32, align 4
+@test2.z = external global i32, align 4

test/test_suite/define/alias_visibility_forbidden.c3

@@ -0,0 +1,2 @@
+alias x @private = y; // #error: A local symbol like
+int y @local = 1;