[dart2js] Better error messaging around invalid annotation.

Also ignore InvalidExpression since the CFE should surface this error itself.

Bug: #62096
Change-Id: I5da48678ca87cf0eb572c1c1c6700557c752f0ce
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/465080
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Nate Biggs <[email protected]>

Author: natebiggs

pkg/compiler/lib/src/kernel/transformations/modular/late_lowering.dart

@@ -754,8 +754,11 @@ class LateLowering {
           ConstantExpression(annotation.constant, annotation.type)
             ..fileOffset = annotation.fileOffset,
         );
-      } else {
-        throw StateError('Non-constant annotation on $source');
+      } else if (annotation is! InvalidExpression) {
+        throw StateError(
+          'Non-constant annotation on $source (${annotation.runtimeType}): '
+          '$annotation',
+        );
       }
     }
   }