[AST Verifier] Don’t ask to compute overridden declarations.

Don’t ask to compute overridden declarations that haven’t already been
computed.

Author: DougGregor

lib/AST/ASTVerifier.cpp

@@ -181,6 +181,16 @@ struct LazyGenericEnvironment {
   }
 };
 
+namespace {
+  /// Retrieve the "overridden" declaration of this declaration, but only if
+  // it's already been computed.
+  template<typename T>
+  T *getOverriddenDeclIfAvailable(T *decl) {
+    if (!decl->overriddenDeclsComputed()) return nullptr;
+
+    return cast_or_null<T>(decl->getOverriddenDecl());
+  }
+}
 class Verifier : public ASTWalker {
   PointerUnion<ModuleDecl *, SourceFile *> M;
   ASTContext &Ctx;
@@ -841,7 +851,7 @@ class Verifier : public ASTWalker {
         }
       }
 
-      if (auto Overridden = D->getOverriddenDecl()) {
+      if (auto Overridden = getOverriddenDeclIfAvailable(D)) {
         if (D->getDeclContext() == Overridden->getDeclContext()) {
           PrettyStackTraceDecl debugStack("verifying overridden", D);
           Out << "cannot override a decl in the same DeclContext";
@@ -2207,38 +2217,40 @@ class Verifier : public ASTWalker {
       }
 
       // Make sure we consistently set accessor overrides.
-      if (auto *baseASD = ASD->getOverriddenDecl()) {
+      if (auto *baseASD = getOverriddenDeclIfAvailable(ASD)) {
         if (ASD->getGetter() && baseASD->getGetter())
-          assert(ASD->getGetter()->getOverriddenDecl() ==
-                 baseASD->getGetter() &&
+          assert(getOverriddenDeclIfAvailable(ASD->getGetter()) ==
+                   baseASD->getGetter() &&
                  "Storage overrides but getter does not");
         if (ASD->getSetter() && baseASD->getSetter() &&
             baseASD->isSetterAccessibleFrom(ASD->getDeclContext()))
-          assert(ASD->getSetter()->getOverriddenDecl() ==
-                 baseASD->getSetter() &&
+          assert(getOverriddenDeclIfAvailable(ASD->getSetter()) ==
+                   baseASD->getSetter() &&
                  "Storage overrides but setter does not");
         if (ASD->getMaterializeForSetFunc() &&
             baseASD->getMaterializeForSetFunc() &&
             baseASD->isSetterAccessibleFrom(ASD->getDeclContext())) {
           if (baseASD->getMaterializeForSetFunc()->hasForcedStaticDispatch()) {
-            assert(ASD->getMaterializeForSetFunc()->getOverriddenDecl() == nullptr
+            assert(getOverriddenDeclIfAvailable(ASD->getMaterializeForSetFunc())
+                     == nullptr
                    && "Forced static dispatch materializeForSet should not be "
                    "overridden");
           } else {
-            assert(ASD->getMaterializeForSetFunc()->getOverriddenDecl() ==
-                   baseASD->getMaterializeForSetFunc() &&
+            assert(getOverriddenDeclIfAvailable(ASD->getMaterializeForSetFunc())
+                     == baseASD->getMaterializeForSetFunc() &&
                    "Storage override but materializeForSet does not");
           }
         }
       } else {
         if (ASD->getGetter())
-          assert(!ASD->getGetter()->getOverriddenDecl() &&
+          assert(!getOverriddenDeclIfAvailable(ASD->getGetter()) &&
                  "Storage does not override but getter does");
         if (ASD->getSetter())
-          assert(!ASD->getSetter()->getOverriddenDecl() &&
+          assert(!getOverriddenDeclIfAvailable(ASD->getSetter()) &&
                  "Storage does not override but setter does");
         if (ASD->getMaterializeForSetFunc())
-          assert(!ASD->getMaterializeForSetFunc()->getOverriddenDecl() &&
+          assert(!getOverriddenDeclIfAvailable(
+                                            ASD->getMaterializeForSetFunc()) &&
                  "Storage does not override but materializeForSet does");
       }