NFC: introduce isAddingConformanceToInvertible

Removes duplicated code between Sema and the ASTPrinter.

(cherry picked from commit 80c9997)

Author: kavon

include/swift/AST/Decl.h

@@ -1912,6 +1912,10 @@ class ExtensionDecl final : public GenericContext, public Decl,
   /// \endcode
   bool isWrittenWithConstraints() const;
 
+  /// Does this extension add conformance to an invertible protocol for the
+  /// extended type?
+  bool isAddingConformanceToInvertible() const;
+
   /// Returns the name of the category specified by the \c \@_objcImplementation
   /// attribute, or \c None if the name is invalid or
   /// \c isObjCImplementation() is false.

lib/AST/ASTPrinter.cpp

@@ -2913,20 +2913,6 @@ void PrintAST::printExtendedTypeName(TypeLoc ExtendedTypeLoc) {
   printTypeLoc(TypeLoc(ExtendedTypeLoc.getTypeRepr(), Ty));
 }
 
-/// If an extension adds a conformance for an invertible protocol, then we
-/// should not print inverses for its generic signature, because no conditional
-/// requirements are inferred by default for such an extension.
-static bool isExtensionAddingInvertibleConformance(const ExtensionDecl *ext) {
-  auto conformances = ext->getLocalConformances();
-  for (auto *conf : conformances) {
-    if (conf->getProtocol()->getInvertibleProtocolKind()) {
-      assert(conformances.size() == 1 && "expected solo conformance");
-      return true;
-    }
-  }
-  return false;
-}
-
 void PrintAST::printSynthesizedExtension(Type ExtendedType,
                                          ExtensionDecl *ExtDecl) {
   if (Options.PrintCompatibilityFeatureChecks &&
@@ -3058,7 +3044,7 @@ void PrintAST::printExtension(ExtensionDecl *decl) {
       // for an invertible protocol itself, as we do not infer any requirements
       // in such an extension. We need to print the whole signature:
       //     extension S: Copyable where T: Copyable
-      if (isExtensionAddingInvertibleConformance(decl)) {
+      if (decl->isAddingConformanceToInvertible()) {
         genSigFlags &= ~PrintInverseRequirements;
         genSigFlags &= ~IncludeOuterInverses;
       }

lib/AST/Decl.cpp

@@ -1894,6 +1894,30 @@ Type ExtensionDecl::getExtendedType() const {
   return ErrorType::get(ctx);
 }
 
+bool ExtensionDecl::isAddingConformanceToInvertible() const {
+  const unsigned numEntries = getInherited().size();
+  for (unsigned i = 0; i < numEntries; ++i) {
+    InheritedTypeRequest request{this, i, TypeResolutionStage::Structural};
+    auto result = evaluateOrDefault(getASTContext().evaluator, request,
+                                    InheritedTypeResult::forDefault());
+    Type inheritedTy;
+    switch (result) {
+    case InheritedTypeResult::Inherited:
+      inheritedTy = result.getInheritedType();
+      break;
+    case InheritedTypeResult::Suppressed:
+    case InheritedTypeResult::Default:
+      continue;
+    }
+
+    if (inheritedTy)
+      if (auto kp = inheritedTy->getKnownProtocol())
+        if (getInvertibleProtocolKind(*kp))
+          return true;
+  }
+  return false;
+}
+
 bool Decl::isObjCImplementation() const {
   return getAttrs().hasAttribute<ObjCImplementationAttr>(/*AllowInvalid=*/true);
 }

lib/Sema/TypeCheckGeneric.cpp

@@ -785,34 +785,10 @@ GenericSignatureRequest::evaluate(Evaluator &evaluator,
   } else if (auto *ext = dyn_cast<ExtensionDecl>(GC)) {
     loc = ext->getLoc();
 
-    // The inherited entries influence the generic signature of the extension,
-    // because if it introduces conformance to invertible protocol IP, we do not
-    // we do not infer any requirements that the generic parameters to conform
+    // If the extension introduces conformance to invertible protocol IP, do not
+    // infer any conditional requirements that the generic parameters to conform
     // to invertible protocols. This forces people to write out the conditions.
-    const unsigned numEntries = ext->getInherited().size();
-    for (unsigned i = 0; i < numEntries; ++i) {
-      InheritedTypeRequest request{ext, i, TypeResolutionStage::Structural};
-      auto result = evaluateOrDefault(ctx.evaluator, request,
-                                      InheritedTypeResult::forDefault());
-      Type inheritedTy;
-      switch (result) {
-      case InheritedTypeResult::Inherited:
-        inheritedTy = result.getInheritedType();
-        break;
-      case InheritedTypeResult::Suppressed:
-      case InheritedTypeResult::Default:
-        continue;
-      }
-
-      if (inheritedTy) {
-        if (auto kp = inheritedTy->getKnownProtocol()) {
-          if (getInvertibleProtocolKind(*kp)) {
-            inferInvertibleReqs = false;
-            break;
-          }
-        }
-      }
-    }
+    inferInvertibleReqs = !ext->isAddingConformanceToInvertible();
 
     collectAdditionalExtensionRequirements(ext->getExtendedType(), extraReqs);