From 776caaf99927181a2bb135afa9b502014782691c Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Sun, 28 Aug 2022 13:37:38 +0300
Subject: [PATCH] Sema: fix handling of non-standard int types in empty
 non-exhaustive enums

Closes #12649
---
 src/Sema.zig           | 15 +++------------
 src/print_zir.zig      | 10 +++++-----
 test/behavior/enum.zig |  5 +++++
 3 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index 17d3b02da3..586f1b2ee8 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -2497,18 +2497,6 @@ fn zirEnumDecl(
     extra_index = try mod.scanNamespace(&enum_obj.namespace, extra_index, decls_len, new_decl);
 
     const body = sema.code.extra[extra_index..][0..body_len];
-    if (fields_len == 0) {
-        assert(body.len == 0);
-        if (tag_type_ref != .none) {
-            const ty = try sema.resolveType(block, tag_ty_src, tag_type_ref);
-            if (ty.zigTypeTag() != .Int and ty.zigTypeTag() != .ComptimeInt) {
-                return sema.fail(block, tag_ty_src, "expected integer tag type, found '{}'", .{ty.fmt(sema.mod)});
-            }
-            enum_obj.tag_ty = try ty.copy(new_decl_arena_allocator);
-            enum_obj.tag_ty_inferred = false;
-        }
-        return decl_val;
-    }
     extra_index += body.len;
 
     const bit_bags_count = std.math.divCeil(usize, fields_len, 32) catch unreachable;
@@ -2566,6 +2554,9 @@ fn zirEnumDecl(
             }
             enum_obj.tag_ty = try ty.copy(decl_arena_allocator);
             enum_obj.tag_ty_inferred = false;
+        } else if (fields_len == 0) {
+            enum_obj.tag_ty = try Type.Tag.int_unsigned.create(decl_arena_allocator, 0);
+            enum_obj.tag_ty_inferred = true;
         } else {
             const bits = std.math.log2_int_ceil(usize, fields_len);
             enum_obj.tag_ty = try Type.Tag.int_unsigned.create(decl_arena_allocator, bits);
diff --git a/src/print_zir.zig b/src/print_zir.zig
index 579a7970b7..f315d7f014 100644
--- a/src/print_zir.zig
+++ b/src/print_zir.zig
@@ -1721,13 +1721,13 @@ const Writer = struct {
         const body = self.code.extra[extra_index..][0..body_len];
         extra_index += body.len;
 
+        const prev_parent_decl_node = self.parent_decl_node;
+        if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
+        try self.writeBracedDecl(stream, body);
         if (fields_len == 0) {
-            assert(body.len == 0);
-            try stream.writeAll("{}, {})");
+            try stream.writeAll(", {})");
+            self.parent_decl_node = prev_parent_decl_node;
         } else {
-            const prev_parent_decl_node = self.parent_decl_node;
-            if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
-            try self.writeBracedDecl(stream, body);
             try stream.writeAll(", {\n");
 
             self.indent += 2;
diff --git a/test/behavior/enum.zig b/test/behavior/enum.zig
index 9e96163cc0..517414780b 100644
--- a/test/behavior/enum.zig
+++ b/test/behavior/enum.zig
@@ -1170,3 +1170,8 @@ test "switch on an extern enum with negative value" {
         Foo.Bar => return,
     }
 }
+
+test "Non-exhaustive enum with nonstandard int size behaves correctly" {
+    const E = enum(u15) { _ };
+    try expect(@sizeOf(E) == @sizeOf(u15));
+}