fix(transformer): emit design:paramtypes when class has static anonymous class expression (#20382)

related https://github.com/rolldown/rolldown/discussions/8684

Fix `design:paramtypes` being silently dropped in release builds when a
decorated class has static properties with anonymous class expression
initializers (`static Foo = class extends Error
  {}`).

`pop_constructor_metadata()` was inside `debug_assert!`, which is a
no-op in release builds, causing stack imbalance and missing metadata.

---------

Co-authored-by: Dunqing <dengqing0821@gmail.com>

crates/oxc_transformer/src/decorator/legacy/mod.rs

@@ -507,10 +507,13 @@ impl<'a> LegacyDecorator<'a> {
             );
         }
 
-        debug_assert!(
-            !self.emit_decorator_metadata || self.metadata.pop_constructor_metadata().is_none(),
-            "`pop_constructor_metadata` should be `None` because there are no class decorators, so no metadata was generated."
-        );
+        if self.emit_decorator_metadata {
+            let metadata = self.metadata.pop_constructor_metadata();
+            debug_assert!(
+                metadata.is_none(),
+                "`pop_constructor_metadata` should be `None` because there are no class decorators, so no metadata was generated."
+            );
+        }
     }
 
     /// Transforms a decorated class declaration and appends the resulting statements. If

tasks/transform_conformance/snapshots/oxc.snap.md

@@ -1,6 +1,6 @@
 commit: 87a048db
 
-Passed: 204/336
+Passed: 204/337
 
 # All Passed:
 * babel-plugin-transform-class-static-block
@@ -555,7 +555,7 @@ x Output mismatch
 x Output mismatch
 
 
-# legacy-decorators (6/87)
+# legacy-decorators (6/88)
 * oxc/class-without-name-with-decorated_class/input.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["dec"]
@@ -854,6 +854,26 @@ Unresolved reference IDs mismatch for "babelHelpers":
 after transform: [ReferenceId(7), ReferenceId(8), ReferenceId(9), ReferenceId(11), ReferenceId(13), ReferenceId(17), ReferenceId(18), ReferenceId(19), ReferenceId(20), ReferenceId(22), ReferenceId(24)]
 rebuilt        : [ReferenceId(0), ReferenceId(3), ReferenceId(5), ReferenceId(6), ReferenceId(8), ReferenceId(9), ReferenceId(12), ReferenceId(14), ReferenceId(16)]
 
+* oxc/metadata/static-anonymous-class-expression/input.ts
+Bindings mismatch:
+after transform: ScopeId(0): ["A", "Foo", "_ref", "dec"]
+rebuilt        : ScopeId(0): ["A", "Foo", "_ref"]
+Symbol reference IDs mismatch for "A":
+after transform: SymbolId(1): [ReferenceId(4), ReferenceId(5), ReferenceId(6)]
+rebuilt        : SymbolId(1): [ReferenceId(7), ReferenceId(8)]
+Symbol span mismatch for "Foo":
+after transform: SymbolId(2): Span { start: 72, end: 75 }
+rebuilt        : SymbolId(2): Span { start: 0, end: 0 }
+Symbol span mismatch for "Foo":
+after transform: SymbolId(5): Span { start: 0, end: 0 }
+rebuilt        : SymbolId(3): Span { start: 72, end: 75 }
+Reference symbol mismatch for "dec":
+after transform: SymbolId(0) "dec"
+rebuilt        : <None>
+Unresolved references mismatch:
+after transform: ["ClassDecorator", "Error", "Object", "babelHelpers"]
+rebuilt        : ["Error", "Object", "babelHelpers", "dec"]
+
 * oxc/metadata/this/input.ts
 Symbol span mismatch for "Example":
 after transform: SymbolId(0): Span { start: 6, end: 13 }

tasks/transform_conformance/tests/legacy-decorators/test/fixtures/oxc/metadata/static-anonymous-class-expression/input.ts

@@ -0,0 +1,10 @@
+declare function dec(): ClassDecorator;
+class A {}
+
+@dec()
+export class Foo {
+  static Error1 = class extends Error {};
+  static Error2 = class extends Error {};
+
+  constructor(a: A) {}
+}

tasks/transform_conformance/tests/legacy-decorators/test/fixtures/oxc/metadata/static-anonymous-class-expression/output.js

@@ -0,0 +1,9 @@
+var _ref;
+class A {}
+let Foo = class Foo {
+  static Error1 = class extends Error {};
+  static Error2 = class extends Error {};
+  constructor(a) {}
+};
+Foo = babelHelpers.decorate([dec(), babelHelpers.decorateMetadata("design:paramtypes", [typeof (_ref = typeof A !== "undefined" && A) === "function" ? _ref : Object])], Foo);
+export { Foo };