Serialization: Skip custom attributes with invalid types.

Prevents a crash during module emission with `-enable-lazy-typechecking` when
the type corresponding to a `CustomAttr` cannot be resolved.

Author: tshortli

include/swift/AST/DiagnosticsSema.def

@@ -811,6 +811,9 @@ ERROR(sema_opening_import,Fatal,
 REMARK(serialization_skipped_invalid_decl,none,
        "serialization skipped invalid %kind0",
        (const Decl *))
+REMARK(serialization_skipped_invalid_type,none,
+       "serialization skipped for invalid type %0",
+       (TypeRepr *))
 ERROR(serialization_failed,none,
       "serialization of module %0 failed due to the errors above",
       (const ModuleDecl *))

lib/Serialization/Serialization.cpp

@@ -3048,12 +3048,12 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
       if (D->getResolvedMacro(const_cast<CustomAttr *>(theAttr)))
         return;
 
-      auto typeID = S.addTypeRef(
-          D->getResolvedCustomAttrType(const_cast<CustomAttr *>(theAttr)));
-      if (!typeID && !S.allowCompilerErrors()) {
-        llvm::PrettyStackTraceString message("CustomAttr has no type");
-        abort();
-      }
+      auto attrType =
+          D->getResolvedCustomAttrType(const_cast<CustomAttr *>(theAttr));
+      if (S.skipTypeIfInvalid(attrType, theAttr->getTypeRepr()))
+        return;
+
+      auto typeID = S.addTypeRef(attrType);
       CustomDeclAttrLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode,
                                        theAttr->isImplicit(),
                                        typeID, theAttr->isArgUnsafe());
@@ -6812,6 +6812,19 @@ bool Serializer::skipDeclIfInvalid(const Decl *decl) {
   return true;
 }
 
+bool Serializer::skipTypeIfInvalid(Type ty, TypeRepr *tyRepr) {
+  if (ty || allowCompilerErrors())
+    return false;
+
+  if (Options.EnableSerializationRemarks) {
+    getASTContext().Diags.diagnose(
+        tyRepr->getLoc(), diag::serialization_skipped_invalid_type, tyRepr);
+  }
+
+  hadError = true;
+  return true;
+}
+
 void serialization::writeToStream(
     raw_ostream &os, ModuleOrSourceFile DC, const SILModule *M,
     const SerializationOptions &options,

lib/Serialization/Serialization.h

@@ -579,6 +579,10 @@ class Serializer : public SerializerBase {
   /// If the declaration is invalid, records that an error occurred and returns
   /// true if the decl should be skipped.
   bool skipDeclIfInvalid(const Decl *decl);
+
+  /// If the type is invalid, records that an error occurred and returns
+  /// true if the type should be skipped.
+  bool skipTypeIfInvalid(Type ty, TypeRepr *tyRepr);
 };
 
 } // end namespace serialization

test/Serialization/lazy-typecheck-errors.swift

@@ -16,3 +16,7 @@ public func returnsInvalidType() -> InvalidType { fatalError() }
 public func takesInvalidType(_ x: InvalidType) {}
 // expected-error@-1 {{cannot find type 'InvalidType' in scope}}
 // expected-serialization-remark@-2 {{serialization skipped invalid global function 'takesInvalidType'}}
+
+@InvalidCustomAttr public struct HasInvalidCustomAttr {}
+// FIXME: An error should be emitted for the invalid attribute
+// expected-serialization-remark@-2 {{serialization skipped for invalid type 'InvalidCustomAttr'}}