From 0a9d6956e7cac96c870ad062b4125b0a0a3b0143 Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Sun, 12 Jun 2022 17:52:30 +0300
Subject: [PATCH] Sema: add missing set_union_tag

---
 lib/std/io/stream_source.zig  |  1 -
 lib/std/json.zig              |  1 -
 lib/std/os/linux/io_uring.zig |  2 --
 src/Sema.zig                  |  4 +++-
 test/behavior/union.zig       | 18 ++++++++++++++++++
 5 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/lib/std/io/stream_source.zig b/lib/std/io/stream_source.zig
index 2345a97855..ce5256028c 100644
--- a/lib/std/io/stream_source.zig
+++ b/lib/std/io/stream_source.zig
@@ -114,7 +114,6 @@ test "StreamSource (mutable buffer)" {
 }
 
 test "StreamSource (const buffer)" {
-    if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest;
     const buffer: [64]u8 = "Hello, World!".* ++ ([1]u8{0xAA} ** 51);
     var source = StreamSource{ .const_buffer = std.io.fixedBufferStream(&buffer) };
 
diff --git a/lib/std/json.zig b/lib/std/json.zig
index 2e09818b6f..cc82c1d0a5 100644
--- a/lib/std/json.zig
+++ b/lib/std/json.zig
@@ -1355,7 +1355,6 @@ pub const Value = union(enum) {
 };
 
 test "Value.jsonStringify" {
-    if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest; // TODO
     {
         var buffer: [10]u8 = undefined;
         var fbs = std.io.fixedBufferStream(&buffer);
diff --git a/lib/std/os/linux/io_uring.zig b/lib/std/os/linux/io_uring.zig
index e7ac17a1af..144927771f 100644
--- a/lib/std/os/linux/io_uring.zig
+++ b/lib/std/os/linux/io_uring.zig
@@ -2154,7 +2154,6 @@ test "timeout (after a number of completions)" {
 }
 
 test "timeout_remove" {
-    if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest; // TODO
     if (builtin.os.tag != .linux) return error.SkipZigTest;
 
     var ring = IO_Uring.init(2, 0) catch |err| switch (err) {
@@ -2951,7 +2950,6 @@ test "provide_buffers: read" {
 }
 
 test "remove_buffers" {
-    if (@import("builtin").zig_backend != .stage1) return error.SkipZigTest; // TODO
     if (builtin.os.tag != .linux) return error.SkipZigTest;
 
     var ring = IO_Uring.init(1, 0) catch |err| switch (err) {
diff --git a/src/Sema.zig b/src/Sema.zig
index f0eb67ec26..5ad9cacff9 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -13757,10 +13757,10 @@ fn zirStructInit(
         const field_type_extra = sema.code.extraData(Zir.Inst.FieldType, field_type_data.payload_index).data;
         const field_name = sema.code.nullTerminatedString(field_type_extra.name_start);
         const field_index = try sema.unionFieldIndex(block, resolved_ty, field_name, field_src);
+        const tag_val = try Value.Tag.enum_field_index.create(sema.arena, field_index);
 
         const init_inst = try sema.resolveInst(item.data.init);
         if (try sema.resolveMaybeUndefVal(block, field_src, init_inst)) |val| {
-            const tag_val = try Value.Tag.enum_field_index.create(sema.arena, field_index);
             return sema.addConstantMaybeRef(
                 block,
                 src,
@@ -13779,6 +13779,8 @@ fn zirStructInit(
             const alloc = try block.addTy(.alloc, alloc_ty);
             const field_ptr = try sema.unionFieldPtr(block, field_src, alloc, field_name, field_src, resolved_ty);
             try sema.storePtr(block, src, field_ptr, init_inst);
+            const new_tag = try sema.addConstant(resolved_ty.unionTagTypeHypothetical(), tag_val);
+            _ = try block.addBinOp(.set_union_tag, alloc, new_tag);
             return alloc;
         }
 
diff --git a/test/behavior/union.zig b/test/behavior/union.zig
index 4daa9c1ee5..caa5d26aea 100644
--- a/test/behavior/union.zig
+++ b/test/behavior/union.zig
@@ -1183,3 +1183,21 @@ test "comptime equality of extern unions with same tag" {
     const b = S.U{ .a = 1234 };
     try expect(S.foo(a) == S.foo(b));
 }
+
+test "union tag is set when initiated as a temporary value at runtime" {
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+
+    const U = union(enum) {
+        a,
+        b: u32,
+        c,
+
+        fn doTheTest(u: @This()) !void {
+            try expect(u == .b);
+        }
+    };
+    var b: u32 = 1;
+    try (U{ .b = b }).doTheTest();
+}