Remove usage of inline for from print_targets.cmdTargets

This function was one of the biggest zig functions in a debug build of
the compiler.

  $ bloaty stage3-debug/bin/zig -d symbols --tsv -n 10000000 |
      rg -v '(llvm|clang|std|lld|\(anonymous namespace\))::|\[section ' |
      sort -h -k 3

  ...
  translate_c.ast.renderNode                    86168   86219
  main.buildOutputType                         177959  178004
  InfoTable                                    184832  184870
  AArch64SVEIntrinsicMap                       188544  188596
  print_targets.cmdTargets__anon_4735          319156  319216
  __static_initialization_and_destruction_0()  486666  489582
  MatchTable1                                  621884  621997
  OperandMatchTable                           1139622 1139861
  MatchTable0                                 1899764 1900141

1 files changed, 27 insertions, 0 deletions

diff --git a/lib/std/meta.zig b/lib/std/meta.zig
index 33f690f7aa..9940fafba0 100644
--- a/lib/std/meta.zig
+++ b/lib/std/meta.zig
@@ -568,6 +568,33 @@ test "std.meta.fieldNames" {
     try testing.expectEqualSlices(u8, u1names[1], "b");
 }
 
+/// Given an enum or error set type, returns a pointer to an array containing all tags for that
+/// enum or error set.
+pub fn tags(comptime T: type) *const [fields(T).len]T {
+    comptime {
+        const fieldInfos = fields(T);
+        var res: [fieldInfos.len]T = undefined;
+        for (fieldInfos) |field, i| {
+            res[i] = @field(T, field.name);
+        }
+        return &res;
+    }
+}
+
+test "std.meta.tags" {
+    const E1 = enum { A, B };
+    const E2 = error{A};
+
+    const e1_tags = tags(E1);
+    const e2_tags = tags(E2);
+
+    try testing.expect(e1_tags.len == 2);
+    try testing.expectEqual(E1.A, e1_tags[0]);
+    try testing.expectEqual(E1.B, e1_tags[1]);
+    try testing.expect(e2_tags.len == 1);
+    try testing.expectEqual(E2.A, e2_tags[0]);
+}
+
 pub fn FieldEnum(comptime T: type) type {
     const field_infos = fields(T);
     var enumFields: [field_infos.len]std.builtin.Type.EnumField = undefined;