From 9195b36a6c55c2f2084d8a2edfd9a98c2e077e8c Mon Sep 17 00:00:00 2001
From: Kendall Condon <goon.pri.low@gmail.com>
Date: Tue, 19 May 2026 19:18:43 -0400
Subject: [PATCH] AstGen: move error capture asserts outside loop

---
 lib/std/zig/AstGen.zig                        |  8 ++--
 .../error_set_cannot_capture_by_reference.zig | 13 -------
 .../switch_capture_error_by_ref.zig           | 25 -------------
 .../switch_on_error_bad_captures_astgen.zig   | 37 +++++++++++++++++++
 .../switch_on_error_bad_captures_sema.zig     | 21 +++++++++++
 ...tch_on_error_with_capture_by_reference.zig | 22 -----------
 6 files changed, 62 insertions(+), 64 deletions(-)
 delete mode 100644 test/cases/compile_errors/error_set_cannot_capture_by_reference.zig
 delete mode 100644 test/cases/compile_errors/switch_capture_error_by_ref.zig
 create mode 100644 test/cases/compile_errors/switch_on_error_bad_captures_astgen.zig
 create mode 100644 test/cases/compile_errors/switch_on_error_bad_captures_sema.zig
 delete mode 100644 test/cases/compile_errors/switch_on_error_with_capture_by_reference.zig

diff --git a/lib/std/zig/AstGen.zig b/lib/std/zig/AstGen.zig
index 6a6bd0ed217906f84cebe87c1d063fbf4f2d2db8..d0e5a6b8a2325f48e00cb2ecc7da74cd0df5b401 100644
--- a/lib/std/zig/AstGen.zig
+++ b/lib/std/zig/AstGen.zig
@@ -7735,10 +7735,6 @@ fn switchExpr(
         };
 
         if (capture != .none) assert(any_has_payload_capture);
-        if (is_err_switch) {
-            assert(!any_payload_is_ref); // should have failed by now
-            assert(!any_has_tag_capture); // should have failed by now
-        }
 
         prong_body: {
             scratch_scope.instructions_top = parent_gz.instructions.items.len;
@@ -7845,6 +7841,10 @@ fn switchExpr(
             }
         }
     }
+    if (is_err_switch) {
+        assert(!any_payload_is_ref); // should have failed by now
+        assert(!any_has_tag_capture); // should have failed by now
+    }
     assert(scalar_case_index + multi_case_index + @intFromBool(has_else) == case_nodes.len);
     assert(multi_items_infos_start + multi_item_offset == bodies_start);
 
diff --git a/test/cases/compile_errors/error_set_cannot_capture_by_reference.zig b/test/cases/compile_errors/error_set_cannot_capture_by_reference.zig
deleted file mode 100644
index d13f85d066983081dd6c2b02f48f1164c2162bde..0000000000000000000000000000000000000000
--- a/test/cases/compile_errors/error_set_cannot_capture_by_reference.zig
+++ /dev/null
@@ -1,13 +0,0 @@
-export fn entry() void {
-    const err: error{Foo} = error.Foo;
-
-    switch (err) {
-        error.Foo => |*foo| {
-            foo catch {};
-        },
-    }
-}
-
-// error
-//
-// :5:23: error: error set cannot be captured by reference
diff --git a/test/cases/compile_errors/switch_capture_error_by_ref.zig b/test/cases/compile_errors/switch_capture_error_by_ref.zig
deleted file mode 100644
index e432159d2c7fbf9f919c0539c6ee75fdd7f08cb5..0000000000000000000000000000000000000000
--- a/test/cases/compile_errors/switch_capture_error_by_ref.zig
+++ /dev/null
@@ -1,25 +0,0 @@
-export fn entry1() void {
-    switch (@as(anyerror, error.MyError)) {
-        error.MyError, error.MyOtherError => |*err| _ = err,
-        else => {},
-    }
-}
-
-export fn entry2() void {
-    switch (@as(anyerror, error.MyError)) {
-        inline error.MyError, error.MyOtherError => |*err| _ = err,
-        else => {},
-    }
-}
-
-export fn entry3() void {
-    switch (@as(anyerror, error.MyError)) {
-        else => |*err| _ = err,
-    }
-}
-
-// error
-//
-// :3:47: error: error set cannot be captured by reference
-// :10:54: error: error set cannot be captured by reference
-// :17:18: error: error set cannot be captured by reference
diff --git a/test/cases/compile_errors/switch_on_error_bad_captures_astgen.zig b/test/cases/compile_errors/switch_on_error_bad_captures_astgen.zig
new file mode 100644
index 0000000000000000000000000000000000000000..97abfcd55fec648f62ccce83c932a461c78c97eb
--- /dev/null
+++ b/test/cases/compile_errors/switch_on_error_bad_captures_astgen.zig
@@ -0,0 +1,37 @@
+const Error = error {OutOfMemory, ReadFailed};
+const result: Error!u64 = error.OutOfMemory;
+
+test {
+    _ = result catch |err| switch (err) {
+        error.ReadFailed => 2,
+        error.OutOfMemory => |*val| 1,
+    };
+}
+
+test {
+    _ = result catch |err| switch (err) {
+        error.ReadFailed => 2,
+        error.OutOfMemory => |_, tag| 1,
+    };
+}
+
+test {
+    _ = if (result) |n| n else |err| switch (err) {
+        error.ReadFailed => 2,
+        error.OutOfMemory => |*val| 1,
+    };
+}
+
+test {
+    _ = if (result) |n| n else |err| switch (err) {
+        error.ReadFailed => 2,
+        error.OutOfMemory => |_, tag| 1,
+    };
+}
+
+// error
+//
+// :7:32: error: error set cannot be captured by reference
+// :14:34: error: cannot capture tag of error union
+// :21:32: error: error set cannot be captured by reference
+// :28:34: error: cannot capture tag of error union
diff --git a/test/cases/compile_errors/switch_on_error_bad_captures_sema.zig b/test/cases/compile_errors/switch_on_error_bad_captures_sema.zig
new file mode 100644
index 0000000000000000000000000000000000000000..6a5ff43818a2905d4ed50ac1b0e2eefdc4c8248d
--- /dev/null
+++ b/test/cases/compile_errors/switch_on_error_bad_captures_sema.zig
@@ -0,0 +1,21 @@
+const Error = error{ OutOfMemory, ReadFailed };
+const err: Error = error.OutOfMemory;
+
+export fn a() void {
+    _ = switch (err) {
+        error.ReadFailed => 2,
+        error.OutOfMemory => |*val| @intFromError(val.*),
+    };
+}
+
+export fn b() void {
+    _ = switch (err) {
+        error.ReadFailed => 2,
+        error.OutOfMemory => |_, tag| @intFromEnum(tag),
+    };
+}
+
+// error
+//
+// :7:31: error: error set cannot be captured by reference
+// :14:34: error: cannot capture tag of non-union type 'error{OutOfMemory,ReadFailed}'
diff --git a/test/cases/compile_errors/switch_on_error_with_capture_by_reference.zig b/test/cases/compile_errors/switch_on_error_with_capture_by_reference.zig
deleted file mode 100644
index d3206d02fe12f024513fcd5d19261251ae32c4f2..0000000000000000000000000000000000000000
--- a/test/cases/compile_errors/switch_on_error_with_capture_by_reference.zig
+++ /dev/null
@@ -1,22 +0,0 @@
-comptime {
-    const e: error{Foo}!u32 = error.Foo;
-    e catch |err| switch (err) {
-        error.Foo => |*foo| {
-            foo catch {};
-        },
-    };
-}
-
-comptime {
-    const e: error{Foo}!u32 = error.Foo;
-    if (e) {} else |err| switch (err) {
-        error.Foo => |*foo| {
-            foo catch {};
-        },
-    }
-}
-
-// error
-//
-// :4:24: error: error set cannot be captured by reference
-// :13:24: error: error set cannot be captured by reference
-- 
2.54.0