From 8c741c617c5e8feac1324b34fc990c8a0850ab22 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Thu, 15 May 2025 09:36:16 +0200
Subject: [PATCH] Variable aliases of aliases would not resolve correctly.
 #2131 Variable aliases could not be assigned to.

---
 releasenotes.md                        |  2 ++
 src/compiler/ast.c                     |  4 ++--
 src/compiler/compiler_internal.h       |  4 ++--
 src/compiler/context.c                 |  4 ++--
 src/compiler/copying.c                 |  2 +-
 src/compiler/enums.h                   |  4 ++--
 src/compiler/json_output.c             |  2 +-
 src/compiler/llvm_codegen.c            |  2 +-
 src/compiler/parse_global.c            |  2 +-
 src/compiler/sema_decls.c              | 15 ++++++++++-----
 src/compiler/sema_expr.c               |  7 ++++---
 src/compiler/sema_liveness.c           |  2 +-
 src/compiler/sema_types.c              |  2 +-
 src/compiler/semantic_analyser.c       |  2 +-
 test/test_suite/define/alias_alias.c3t | 21 +++++++++++++++++++++
 15 files changed, 52 insertions(+), 23 deletions(-)
 create mode 100644 test/test_suite/define/alias_alias.c3t

diff --git a/releasenotes.md b/releasenotes.md
index 98f01711d..1867a9b2b 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -19,6 +19,8 @@
 - attrdef with any invalid name causes compiler assert #2128.
 - Correctly error on `@attrdef Foo = ;`.
 - Contract on trying to use Object without initializing it.
+- Variable aliases of aliases would not resolve correctly. #2131
+- Variable aliases could not be assigned to.
 
 ### Stdlib changes
 - Added `String.quick_ztr` and `String.is_zstr`
diff --git a/src/compiler/ast.c b/src/compiler/ast.c
index 965ddfadd..8ec7d81bf 100644
--- a/src/compiler/ast.c
+++ b/src/compiler/ast.c
@@ -112,7 +112,7 @@ const char *decl_to_a_name(Decl *decl)
 		case DECL_CT_EXEC: return "compile time exec include";
 		case DECL_CT_INCLUDE: return "an include";
 		case DECL_DECLARRAY: return "a declarray";
-		case DECL_DEFINE: case DECL_TYPEDEF: return "a define";
+		case DECL_ALIAS: case DECL_TYPEDEF: return "an alias";
 		case DECL_DISTINCT: return "a distinct type";
 		case DECL_ENUM: return "an enum";
 		case DECL_ENUM_CONSTANT: return "an enum value";
@@ -401,7 +401,7 @@ bool decl_needs_prefix(Decl *decl)
 	switch (decl->decl_kind)
 	{
 		case DECL_VAR:
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 		case DECL_FUNC:
 		case DECL_MACRO:
 		case DECL_FAULT:
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index 37804792d..32f3997b8 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -3200,7 +3200,7 @@ INLINE bool decl_poison(Decl *decl)
 
 static inline Decl *decl_raw(Decl *decl)
 {
-	while (decl->decl_kind == DECL_DEFINE)
+	while (decl->decl_kind == DECL_ALIAS)
 	{
 		decl = decl->define_decl.alias;
 	}
@@ -3227,7 +3227,7 @@ INLINE bool decl_is_user_defined_type(Decl *decl)
 
 INLINE Decl *decl_flatten(Decl *decl)
 {
-	if (decl->decl_kind == DECL_DEFINE)
+	if (decl->decl_kind == DECL_ALIAS)
 	{
 		return decl->define_decl.alias;
 	}
diff --git a/src/compiler/context.c b/src/compiler/context.c
index 4de2311ab..47c8d541d 100644
--- a/src/compiler/context.c
+++ b/src/compiler/context.c
@@ -175,7 +175,7 @@ void decl_register(Decl *decl)
 		case DECL_STRUCT:
 		case DECL_TYPEDEF:
 		case DECL_UNION:
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 		case DECL_FUNC:
 		case DECL_MACRO:
 		case DECL_VAR:
@@ -248,7 +248,7 @@ void unit_register_global_decl(CompilationUnit *unit, Decl *decl)
 			vec_add(unit->faults, decl);
 			decl_register(decl);
 			break;
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 			ASSERT(decl->name);
 			vec_add(unit->generic_defines, decl);
 			decl_register(decl);
diff --git a/src/compiler/copying.c b/src/compiler/copying.c
index e9d2992ac..78ba9808b 100644
--- a/src/compiler/copying.c
+++ b/src/compiler/copying.c
@@ -1103,7 +1103,7 @@ Decl *copy_decl(CopyStruct *c, Decl *decl)
 			MACRO_COPY_DECL_LIST(decl->attr_decl.params);
 			decl->attr_decl.attrs = copy_attributes(c, decl->attr_decl.attrs);
 			break;
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 			if (decl->resolve_status == RESOLVE_DONE)
 			{
 				fixup_decl(c, &decl->define_decl.alias);
diff --git a/src/compiler/enums.h b/src/compiler/enums.h
index 7bba26579..961214ed3 100644
--- a/src/compiler/enums.h
+++ b/src/compiler/enums.h
@@ -659,7 +659,7 @@ typedef enum
 	DECL_CT_EXEC,
 	DECL_CT_INCLUDE,
 	DECL_DECLARRAY,
-	DECL_DEFINE,
+	DECL_ALIAS,
 	DECL_DISTINCT,
 	DECL_ENUM,
 	DECL_ENUM_CONSTANT,
@@ -1630,7 +1630,7 @@ typedef enum
 // -- Decl helper macros
 #define NON_TYPE_DECLS DECL_IMPORT: case DECL_MACRO: \
 	case DECL_DECLARRAY: case DECL_ATTRIBUTE: case DECL_LABEL: \
-	case DECL_DEFINE: case DECL_CT_ASSERT: case DECL_CT_EXEC: case DECL_FAULT: \
+	case DECL_ALIAS: case DECL_CT_ASSERT: case DECL_CT_EXEC: case DECL_FAULT: \
 	case DECL_CT_ECHO: case DECL_CT_INCLUDE: case DECL_GROUP: \
 	case DECL_BODYPARAM: case DECL_VAR: case DECL_ENUM_CONSTANT: \
 	case DECL_POISONED
diff --git a/src/compiler/json_output.c b/src/compiler/json_output.c
index 2767e7236..3cb44d0cf 100644
--- a/src/compiler/json_output.c
+++ b/src/compiler/json_output.c
@@ -87,7 +87,7 @@ static inline const char *decl_type_to_string(Decl *type)
 		case DECL_CT_ECHO: return "$echo";
 		case DECL_CT_EXEC: return "$exec";
 		case DECL_CT_INCLUDE: return "$include";
-		case DECL_DEFINE: return "def";
+		case DECL_ALIAS: return "alias";
 		case DECL_DISTINCT: return "typedef";
 		case DECL_ENUM: return "enum";
 		case DECL_ENUM_CONSTANT: return "enum_const";
diff --git a/src/compiler/llvm_codegen.c b/src/compiler/llvm_codegen.c
index 0eb945899..9be75411d 100644
--- a/src/compiler/llvm_codegen.c
+++ b/src/compiler/llvm_codegen.c
@@ -1345,7 +1345,7 @@ LLVMValueRef llvm_get_ref(GenContext *c, Decl *decl)
 			llvm_append_function_attributes(c, decl);
 			llvm_set_decl_linkage(c, decl);
 			return backend_ref;
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 			return llvm_get_ref(c, decl->define_decl.alias);
 		case DECL_FAULT:
 			return llvm_create_fault(c, decl);
diff --git a/src/compiler/parse_global.c b/src/compiler/parse_global.c
index 04266984b..e7f55f029 100644
--- a/src/compiler/parse_global.c
+++ b/src/compiler/parse_global.c
@@ -2174,7 +2174,7 @@ static inline Decl *parse_alias_ident(ParseContext *c)
 	}
 
 	// 3. Set up the "define".
-	Decl *decl = decl_new(DECL_DEFINE, symstr(c), c->span);
+	Decl *decl = decl_new(DECL_ALIAS, symstr(c), c->span);
 
 	if (decl->name == kw_main)
 	{
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index 4e54e01dd..81560d008 100755
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -53,7 +53,7 @@ static Decl *sema_find_exact_typed_operator_in_list(Decl **methods, OperatorOver
 
 static inline bool sema_analyse_typedef(SemaContext *context, Decl *decl, bool *erase_decl);
 static bool sema_analyse_variable_type(SemaContext *context, Type *type, SourceSpan span);
-static inline bool sema_analyse_define(SemaContext *context, Decl *decl, bool *erase_decl);
+static inline bool sema_analyse_alias(SemaContext *context, Decl *decl, bool *erase_decl);
 static inline bool sema_analyse_distinct(SemaContext *context, Decl *decl, bool *erase_decl);
 
 static CompilationUnit *unit_copy(Module *module, CompilationUnit *unit);
@@ -4965,7 +4965,7 @@ static inline bool sema_analyse_attribute_decl(SemaContext *context, SemaContext
 	return true;
 }
 
-static inline bool sema_analyse_define(SemaContext *context, Decl *decl, bool *erase_decl)
+static inline bool sema_analyse_alias(SemaContext *context, Decl *decl, bool *erase_decl)
 {
 	if (!sema_analyse_attributes(context, decl, decl->attributes, ATTR_ALIAS, erase_decl)) return decl_poison(decl);
 	if (*erase_decl) return true;
@@ -4981,7 +4981,12 @@ static inline bool sema_analyse_define(SemaContext *context, Decl *decl, bool *e
 		RETURN_SEMA_ERROR(expr, "A global variable or function name was expected here.");
 	}
 	Decl *symbol = expr->ident_expr;
-	if (!sema_analyse_decl(context, symbol)) return false;
+	while (true)
+	{
+		if (!sema_analyse_decl(context, symbol)) return false;
+		if (symbol->decl_kind != DECL_ALIAS) break;
+		symbol = symbol->define_decl.alias;
+	}
 	bool should_be_const = char_is_upper(decl->name[0]);
 	if (should_be_const)
 	{
@@ -5136,8 +5141,8 @@ bool sema_analyse_decl(SemaContext *context, Decl *decl)
 		case DECL_FAULT:
 			if (!sema_analyse_fault(context, decl, &erase_decl)) goto FAILED;
 			break;
-		case DECL_DEFINE:
-			if (!sema_analyse_define(context, decl, &erase_decl)) goto FAILED;
+		case DECL_ALIAS:
+			if (!sema_analyse_alias(context, decl, &erase_decl)) goto FAILED;
 			break;
 		case DECL_POISONED:
 		case DECL_IMPORT:
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index a14c3a550..2ef5bce52 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -798,7 +798,7 @@ static inline bool sema_cast_ident_rvalue(SemaContext *context, Expr *expr)
 		case DECL_IMPORT:
 		case DECL_ATTRIBUTE:
 		case DECL_CT_ASSERT:
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 		case DECL_CT_ECHO:
 			UNREACHABLE
 		case DECL_POISONED:
@@ -1065,7 +1065,7 @@ static inline bool sema_expr_analyse_identifier(SemaContext *context, Type *to,
 				case DECL_MACRO:
 					message = "Macros from other modules must be prefixed with the module name.";
 					break;
-				case DECL_DEFINE:
+				case DECL_ALIAS:
 					message = "Aliases from other modules must be prefixed with the module name.";
 					break;
 				case DECL_FAULT:
@@ -1085,6 +1085,7 @@ static inline bool sema_expr_analyse_identifier(SemaContext *context, Type *to,
 	sema_display_deprecated_warning_on_use(decl, expr->span);
 
 	unit_register_external_symbol(context, decl);
+	decl = decl_flatten(decl);
 	if (decl->decl_kind == DECL_VAR)
 	{
 		decl->var.is_read = true;
@@ -9089,7 +9090,7 @@ static inline bool sema_expr_analyse_ct_nameof(SemaContext *context, Expr *expr)
 			case DECL_IMPORT:
 			case DECL_LABEL:
 			case DECL_MACRO:
-			case DECL_DEFINE:
+			case DECL_ALIAS:
 				RETURN_SEMA_ERROR(main_var, "'%s' does not have an external name.", decl->name);
 			case DECL_FAULT:
 				goto RETURN_CT;
diff --git a/src/compiler/sema_liveness.c b/src/compiler/sema_liveness.c
index 62f0cb5f8..93cdc13c1 100644
--- a/src/compiler/sema_liveness.c
+++ b/src/compiler/sema_liveness.c
@@ -594,7 +594,7 @@ RETRY:
 		case DECL_TYPEDEF:
 			sema_trace_type_liveness(decl->type);
 			return;
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 			decl = decl->define_decl.alias;
 			goto RETRY;
 		case DECL_ENUM:
diff --git a/src/compiler/sema_types.c b/src/compiler/sema_types.c
index feb0b4089..c7bdafe68 100644
--- a/src/compiler/sema_types.c
+++ b/src/compiler/sema_types.c
@@ -256,7 +256,7 @@ static bool sema_resolve_type_identifier(SemaContext *context, TypeInfo *type_in
 				return true;
 			}
 			FALLTHROUGH;
-		case DECL_DEFINE:
+		case DECL_ALIAS:
 		case DECL_FUNC:
 		case DECL_ENUM_CONSTANT:
 		case DECL_IMPORT:
diff --git a/src/compiler/semantic_analyser.c b/src/compiler/semantic_analyser.c
index e710fa7bc..fd32f7d5c 100644
--- a/src/compiler/semantic_analyser.c
+++ b/src/compiler/semantic_analyser.c
@@ -240,7 +240,7 @@ static void register_generic_decls(CompilationUnit *unit, Decl **decls)
 			case DECL_BODYPARAM:
 			case DECL_GROUP:
 				UNREACHABLE
-			case DECL_DEFINE:
+			case DECL_ALIAS:
 			case DECL_DISTINCT:
 			case DECL_ENUM:
 			case DECL_STRUCT:
diff --git a/test/test_suite/define/alias_alias.c3t b/test/test_suite/define/alias_alias.c3t
new file mode 100644
index 000000000..71f075c94
--- /dev/null
+++ b/test/test_suite/define/alias_alias.c3t
@@ -0,0 +1,21 @@
+// #target: macos-x64
+module test;
+int x = 0;
+alias y = x;
+alias z = y;
+alias w = z;
+fn int main()
+{
+	z = 4;
+	w = 3;
+	return 0;
+}
+
+/* #expect: test.ll
+
+entry:
+  store i32 4, ptr @test.x, align 4
+  store i32 3, ptr @test.x, align 4
+  ret i32 0
+}
+