From 1f64f4707e14636a160bc695dc0c4add154bb4e2 Mon Sep 17 00:00:00 2001
From: dimgigov <gigov@gigov.org>
Date: Fri, 5 Jun 2026 22:47:37 +0300
Subject: [PATCH] fix: algebraic enum C backend and sema field type resolution

- Fix sema.nim: use objType.name instead of obj.name for algebraic enum
  tag/data field types (was generating _Tag instead of EnumName_Tag)
- Fix c_backend.nim: emit enum definitions before struct definitions
  to allow structs to reference algebraic enum types
---
 compiler/bootstrap/c_backend.nim | 16 ++++++++++++----
 compiler/bootstrap/sema.nim      |  6 +++---
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/compiler/bootstrap/c_backend.nim b/compiler/bootstrap/c_backend.nim
index 1344b99..430016c 100644
--- a/compiler/bootstrap/c_backend.nim
+++ b/compiler/bootstrap/c_backend.nim
@@ -616,14 +616,22 @@ proc emitModule*(be: var CBackend, module: HirModule): string =
         be.emitLine(&"/* const {c.name} (complex expression) */")
     be.emitLine("")
 
+  # Forward declarations for all structs
+  for s in module.structs:
+    be.emitLine(&"typedef struct {s.name} {s.name};")
+  if module.structs.len > 0:
+    be.emitLine("")
+
+  # Enum definitions (must come before structs that reference them)
+  for e in module.enums:
+    be.emitEnum(e.name, e.variants)
+  if module.enums.len > 0:
+    be.emitLine("")
+
   # Struct definitions
   for s in module.structs:
     be.emitStruct(s.name, s.fields)
 
-  # Enum definitions
-  for e in module.enums:
-    be.emitEnum(e.name, e.variants)
-
   # Slice fat-pointer typedefs
   if sliceTypes.len > 0:
     be.emitLine("/* Slice types */")
diff --git a/compiler/bootstrap/sema.nim b/compiler/bootstrap/sema.nim
index 7d78f98..f608698 100644
--- a/compiler/bootstrap/sema.nim
+++ b/compiler/bootstrap/sema.nim
@@ -1086,11 +1086,11 @@ proc checkExpr(sema: var Sema, expr: Expr, scope: Scope): Type =
           elif sym.decl.kind == dkEnum:
             # Algebraic enum fields
             if expr.exprFieldName == "tag":
-              return makeNamed(obj.name & "_Tag")
+              return makeNamed(objType.name & "_Tag")
             elif expr.exprFieldName == "data":
-              return makeNamed(obj.name & "_Data")
+              return makeNamed(objType.name & "_Data")
             else:
-              sema.emitError(expr.loc, &"enum '{obj.name}' has no field '{expr.exprFieldName}'")
+              sema.emitError(expr.loc, &"enum '{objType.name}' has no field '{expr.exprFieldName}'")
           elif sym.decl.kind == dkUnion:
             # Union fields
             for f in sym.decl.declUnionFields: