From d71f339395f8a3a3c09bbb2d51e6f35cb5295d14 Mon Sep 17 00:00:00 2001
From: Tadeo Kondrak <me@tadeo.ca>
Date: Fri, 25 Sep 2020 17:14:13 -0600
Subject: [PATCH] stage1: disallow fields in opaque types

---
 src/stage1/analyze.cpp  | 16 ++++++++++++----
 test/compile_errors.zig | 10 ++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/stage1/analyze.cpp b/src/stage1/analyze.cpp
index 6008496fe2..b22f0ef393 100644
--- a/src/stage1/analyze.cpp
+++ b/src/stage1/analyze.cpp
@@ -3457,10 +3457,18 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
 }
 
 static Error resolve_opaque_type(CodeGen *g, ZigType *opaque_type) {
-    opaque_type->abi_align = UINT32_MAX;
-    opaque_type->abi_size = SIZE_MAX;
-    opaque_type->size_in_bits = SIZE_MAX;
-    return ErrorNone;
+    Error err = ErrorNone;
+    AstNode *container_node = opaque_type->data.opaque.decl_node;
+    if (container_node != nullptr) {
+        assert(container_node->type == NodeTypeContainerDecl);
+        AstNodeContainerDecl *container_decl = &container_node->data.container_decl;
+        for (int i = 0; i < container_decl->fields.length; i++) {
+            AstNode *field_node = container_decl->fields.items[i];
+            add_node_error(g, field_node, buf_create_from_str("opaque types cannot have fields"));
+            err = ErrorSemanticAnalyzeFail;
+        }
+    }
+    return err;
 }
 
 void append_namespace_qualification(CodeGen *g, Buf *buf, ZigType *container_type) {
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index f19e3c44c1..6c2e96fc5e 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -125,6 +125,16 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
         "tmp.zig:15:23: error: enum field missing: 'arst'",
         "tmp.zig:27:24: note: referenced here",
     });
+
+    cases.add("opaque type with field",
+        \\const Opaque = opaque { foo: i32 };
+        \\export fn entry() void {
+        \\    const foo: ?*Opaque = null;
+        \\}
+    , &[_][]const u8{
+        "tmp.zig:1:25: error: opaque types cannot have fields",
+    });
+
     cases.add("@Type(.Fn) with is_generic = true",
         \\const Foo = @Type(.{
         \\    .Fn = .{