[Serialization] Drop overriding relationship in constructors when safe

lib/Serialization/Deserialization.cpp

@@ -3094,7 +3094,7 @@ class DeclDeserializer {
     GenericSignatureID genericSigID;
     uint8_t storedInitKind, rawAccessLevel;
     DeclID overriddenID;
-    bool needsNewVTableEntry, firstTimeRequired;
+    bool overriddenAffectsABI, needsNewVTableEntry, firstTimeRequired;
     unsigned numArgNames;
     ArrayRef<uint64_t> argNameAndDependencyIDs;
 
@@ -3104,6 +3104,7 @@ class DeclDeserializer {
                                                async, throws, storedInitKind,
                                                genericSigID,
                                                overriddenID,
+                                               overriddenAffectsABI,
                                                rawAccessLevel,
                                                needsNewVTableEntry,
                                                firstTimeRequired,
@@ -3130,15 +3131,25 @@ class DeclDeserializer {
       attrs.setRawAttributeChain(DAttrs);
     }
 
-    auto overridden = MF.getDeclChecked(overriddenID);
-    if (!overridden) {
-      // Pass through deserialization errors.
-      if (overridden.errorIsA<FatalDeserializationError>())
-        return overridden.takeError();
+    Expected<Decl *> overriddenOrError = MF.getDeclChecked(overriddenID);
+    Decl *overridden;
+    if (overriddenOrError) {
+      overridden = overriddenOrError.get();
+    } else if (overriddenOrError.errorIsA<FatalDeserializationError>()) {
+      // Pass through fatal deserialization errors.
+      return overriddenOrError.takeError();
+    } else if (MF.allowCompilerErrors()) {
+      // Drop overriding relationship when allowing errors.
+      llvm::consumeError(overriddenOrError.takeError());
+      overridden = nullptr;
+    } else {
+      llvm::consumeError(overriddenOrError.takeError());
+      if (overriddenAffectsABI || !ctx.LangOpts.EnableDeserializationRecovery) {
+        return llvm::make_error<OverrideError>(name, errorFlags,
+                                               numVTableEntries);
+      }
 
-      llvm::consumeError(overridden.takeError());
-      return llvm::make_error<OverrideError>(
-          name, errorFlags, numVTableEntries);
+      overridden = nullptr;
     }
 
     for (auto dependencyID : argNameAndDependencyIDs.slice(numArgNames)) {
@@ -3198,7 +3209,7 @@ class DeclDeserializer {
     ctx.evaluator.cacheOutput(NeedsNewVTableEntryRequest{ctor},
                               std::move(needsNewVTableEntry));
 
-    ctor->setOverriddenDecl(cast_or_null<ConstructorDecl>(overridden.get()));
+    ctor->setOverriddenDecl(cast_or_null<ConstructorDecl>(overridden));
     if (auto *overridden = ctor->getOverriddenDecl()) {
       if (!attributeChainContains<RequiredAttr>(DAttrs) ||
           !overridden->isRequired()) {

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 741; // SIL pack types
+const uint16_t SWIFTMODULE_VERSION_MINOR = 742; // Constructor affects ABI
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -1455,6 +1455,7 @@ namespace decls_block {
     CtorInitializerKindField,  // initializer kind
     GenericSignatureIDField, // generic environment
     DeclIDField, // overridden decl
+    BCFixed<1>,   // whether the overridden decl affects ABI
     AccessLevelField, // access level
     BCFixed<1>,   // requires a new vtable slot
     BCFixed<1>,   // 'required' but overridden is not (used for recovery)

lib/Serialization/Serialization.cpp

@@ -3535,17 +3535,20 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
     // its overrides after they've been compiled: if the declaration is '@objc'
     // and 'dynamic'. In that case, all accesses to the method or property will
     // go through the Objective-C method tables anyway.
-    if (overridden->hasClangNode() || overridden->shouldUseObjCDispatch())
+    if (!isa<ConstructorDecl>(override) &&
+        (overridden->hasClangNode() || overridden->shouldUseObjCDispatch()))
       return false;
 
     // In a public-override-internal case, the override doesn't have ABI
-    // implications.
+    // implications. This corresponds to hiding the override keyword from the
+    // module interface.
     auto isPublic = [](const ValueDecl *VD) {
       return VD->getFormalAccessScope(VD->getDeclContext(),
                                       /*treatUsableFromInlineAsPublic*/true)
                .isPublic();
     };
-    if (isPublic(override) && !isPublic(overridden))
+    if (override->getDeclContext()->getParentModule()->isResilient() &&
+        isPublic(override) && !isPublic(overridden))
       return false;
 
     return true;
@@ -4499,9 +4502,12 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
     uint8_t rawAccessLevel = getRawStableAccessLevel(ctor->getFormalAccess());
 
     bool firstTimeRequired = ctor->isRequired();
-    if (auto *overridden = ctor->getOverriddenDecl())
+    auto *overridden = ctor->getOverriddenDecl();
+    if (overridden) {
       if (firstTimeRequired && overridden->isRequired())
         firstTimeRequired = false;
+    }
+    bool overriddenAffectsABI = overriddenDeclAffectsABI(ctor, overridden);
 
     unsigned abbrCode = S.DeclTypeAbbrCodes[ConstructorLayout::Code];
     ConstructorLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode,
@@ -4517,7 +4523,8 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
                                     ctor->getInitKind()),
                                   S.addGenericSignatureRef(
                                                  ctor->getGenericSignature()),
-                                  S.addDeclRef(ctor->getOverriddenDecl()),
+                                  S.addDeclRef(overridden),
+                                  overriddenAffectsABI,
                                   rawAccessLevel,
                                   ctor->needsNewVTableEntry(),
                                   firstTimeRequired,

test/Serialization/Safety/override-internal-func.swift

@@ -19,6 +19,8 @@
 //--- Lib.swift
 
 open class Base {
+  internal init() {}
+
   public func publicMethod() -> Int {
     return 1
   }
@@ -33,6 +35,10 @@ open class Base {
 }
 
 open class Derived : Base {
+  public override init() {
+      super.init()
+  }
+
   open override func publicMethod() -> Int {
     return super.publicMethod() + 1
   }
@@ -63,3 +69,7 @@ public class OtherFinalDerived : Derived {
     return super.internalMethod() + 1
   }
 }
+
+func foo() {
+    let a = Derived()
+}