[Type checker] Refactor override checking

include/swift/AST/Attr.h

@@ -1385,7 +1385,7 @@ class DeclAttributes {
   /// Retrieve the first attribute of the given attribute class.
   template <typename ATTR>
   const ATTR *getAttribute(bool AllowInvalid = false) const {
-    return const_cast<DeclAttributes *>(this)->getAttribute<ATTR>();
+    return const_cast<DeclAttributes *>(this)->getAttribute<ATTR>(AllowInvalid);
   }
 
   template <typename ATTR>

include/swift/AST/DiagnosticsSema.def

@@ -1976,15 +1976,6 @@ NOTE(overridden_here,none,
 NOTE(overridden_here_can_be_objc,none,
      "add '@objc' to make this declaration overridable", ())
 
-ERROR(override_objc_type_mismatch_method,none,
-      "overriding method with selector %0 has incompatible type %1",
-      (ObjCSelector, Type))
-ERROR(override_objc_type_mismatch_subscript,none,
-      "overriding %select{|indexed |keyed }0subscript with incompatible type "
-      "%1",
-      (unsigned, Type))
-NOTE(overridden_here_with_type,none,
-     "overridden declaration here has type %0", (Type))
 ERROR(missing_override,none,
       "overriding declaration requires an 'override' keyword", ())
 

lib/AST/NameLookup.cpp

@@ -84,13 +84,8 @@ bool swift::removeOverriddenDecls(SmallVectorImpl<ValueDecl*> &decls) {
   if (decls.size() < 2)
     return false;
 
-  auto lazyResolver = decls.front()->getASTContext().getLazyResolver();
   llvm::SmallPtrSet<ValueDecl*, 8> overridden;
   for (auto decl : decls) {
-    // Compute enough information to make the overridden-declaration available.
-    if (lazyResolver)
-      lazyResolver->resolveOverriddenDecl(decl);
-
     while (auto overrides = decl->getOverriddenDecl()) {
       overridden.insert(overrides);
 
@@ -105,10 +100,6 @@ bool swift::removeOverriddenDecls(SmallVectorImpl<ValueDecl*> &decls) {
         ///        cause instead (incomplete circularity detection).
         assert(decl != overrides && "Circular class inheritance?");
         decl = overrides;
-
-        if (lazyResolver)
-          lazyResolver->resolveOverriddenDecl(decl);
-
         continue;
       }
 
@@ -1908,9 +1899,6 @@ bool DeclContext::lookupQualified(Type type,
       // If the declaration has an override, name lookup will also have
       // found the overridden method. Skip this declaration, because we
       // prefer the overridden method.
-      if (typeResolver)
-        typeResolver->resolveOverriddenDecl(decl);
-
       if (decl->getOverriddenDecl())
         continue;
 

lib/ClangImporter/ImportDecl.cpp

@@ -6389,6 +6389,12 @@ ConstructorDecl *SwiftDeclConverter::importConstructor(
 }
 
 void SwiftDeclConverter::recordObjCOverride(AbstractFunctionDecl *decl) {
+  // Make sure that we always set the overriden declarations.
+  SWIFT_DEFER {
+    if (!decl->overriddenDeclsComputed())
+      (void)decl->setOverriddenDecls({ });
+  };
+
   // Figure out the class in which this method occurs.
   if (!decl->getDeclContext()->isTypeContext())
     return;
@@ -6419,6 +6425,7 @@ void SwiftDeclConverter::recordObjCOverride(AbstractFunctionDecl *decl) {
           func->getObjCSelector() != foundFunc->getObjCSelector())
         continue;
       func->setOverriddenDecl(foundFunc);
+      func->getAttrs().add(new (func->getASTContext()) OverrideAttr(true));
       return;
     }
     // Set constructor override.
@@ -6429,6 +6436,8 @@ void SwiftDeclConverter::recordObjCOverride(AbstractFunctionDecl *decl) {
         ctor->getObjCSelector() != memberCtor->getObjCSelector())
       continue;
     ctor->setOverriddenDecl(memberCtor);
+    ctor->getAttrs().add(new (ctor->getASTContext()) OverrideAttr(true));
+
     // Propagate 'required' to subclass initializers.
     if (memberCtor->isRequired() &&
         !ctor->getAttrs().hasAttribute<RequiredAttr>()) {