Re-apply "[migrator] migrator: avoid inserting base name while renaming

if users' member access doesn't specify the base name. rdar://40373279"

Previously, we saw that unconditionally omitting type names can lead to
build errors (rdar://40458118). This revised fix omits type names only when
the new member name is identical to the old one.

Author: nkcsgexi

lib/Migrator/APIDiffMigratorPass.cpp

@@ -273,6 +273,21 @@ struct APIDiffMigratorPass : public ASTMigratorPass, public SourceEntityWalker {
       SF->getASTContext().SourceMgr, Range).str() == "nil";
   }
 
+  bool isDotMember(CharSourceRange Range) {
+    auto S = Range.str();
+    return S.startswith(".") && S.substr(1).find(".") == StringRef::npos;
+  }
+
+  bool isDotMember(SourceRange Range) {
+    return isDotMember(Lexer::getCharSourceRangeFromSourceRange(
+      SF->getASTContext().SourceMgr, Range));
+  }
+
+  bool isDotMember(Expr *E) {
+    auto Range = E->getSourceRange();
+    return Range.isValid() && isDotMember(Range);
+  }
+
   std::vector<APIDiffItem*> getRelatedDiffItems(ValueDecl *VD) {
     std::vector<APIDiffItem*> results;
     if (!VD)
@@ -323,11 +338,13 @@ struct APIDiffMigratorPass : public ASTMigratorPass, public SourceEntityWalker {
   }
 
 
-  bool isSimpleReplacement(APIDiffItem *Item, std::string &Text) {
+  bool isSimpleReplacement(APIDiffItem *Item, bool isDotMember, std::string &Text) {
     if (auto *MD = dyn_cast<TypeMemberDiffItem>(Item)) {
       if (MD->Subkind == TypeMemberDiffItemSubKind::SimpleReplacement) {
-        Text = (llvm::Twine(MD->newTypeName) + "." + MD->getNewName().base()).
-          str();
+        bool NeedNoTypeName = isDotMember &&
+          MD->oldPrintedName == MD->newPrintedName;
+        Text = (llvm::Twine(NeedNoTypeName ? "" : MD->newTypeName) + "." +
+          MD->getNewName().base()).str();
         return true;
       }
     }
@@ -423,7 +440,7 @@ struct APIDiffMigratorPass : public ASTMigratorPass, public SourceEntityWalker {
                           Type T, ReferenceMetaData Data) override {
     for (auto *Item: getRelatedDiffItems(CtorTyRef ? CtorTyRef: D)) {
       std::string RepText;
-      if (isSimpleReplacement(Item, RepText)) {
+      if (isSimpleReplacement(Item, isDotMember(Range), RepText)) {
         Editor.replace(Range, RepText);
         return true;
       }
@@ -498,8 +515,11 @@ struct APIDiffMigratorPass : public ASTMigratorPass, public SourceEntityWalker {
       for (auto *I: getRelatedDiffItems(VD)) {
         if (auto *Item = dyn_cast<TypeMemberDiffItem>(I)) {
           if (Item->Subkind == TypeMemberDiffItemSubKind::QualifiedReplacement) {
-            Editor.replace(ToReplace, (llvm::Twine(Item->newTypeName) + "." +
-              Item->getNewName().base()).str());
+            bool NeedNoTypeName = isDotMember(ToReplace) &&
+              Item->oldPrintedName == Item->newPrintedName;
+            Editor.replace(ToReplace,
+              (llvm::Twine(NeedNoTypeName ? "" : Item->newTypeName) + "." +
+               Item->getNewName().base()).str());
             return true;
           }
         }
@@ -773,7 +793,7 @@ struct APIDiffMigratorPass : public ASTMigratorPass, public SourceEntityWalker {
     StringRef LeftComment;
     StringRef RightComment;
     for (auto *Item: getRelatedDiffItems(RD)) {
-      if (isSimpleReplacement(Item, Rename)) {
+      if (isSimpleReplacement(Item, isDotMember(Reference), Rename)) {
       } else if (auto *CI = dyn_cast<CommonDiffItem>(Item)) {
         if (CI->isStringRepresentableChange() &&
             CI->NodeKind == SDKNodeKind::DeclVar) {

test/Migrator/Inputs/qualified.json

@@ -38,5 +38,13 @@
     "OldTypeName": "",
     "NewPrintedName": "internalType",
     "NewTypeName": "ToplevelWrapper"
-  }
+  },
+  {
+    "DiffItemKind": "TypeMemberDiffItem",
+    "Usr": "c:@E@FooComparisonResult@FooOrderedMemberSame",
+    "OldPrintedName": "orderedMemberSame",
+    "OldTypeName": "FooComparisonResult",
+    "NewPrintedName": "orderedMemberSame",
+    "NewTypeName": "NewFooComparisonResult.Nested"
+  },
 ]

test/Migrator/mock-sdk/Bar.framework/Headers/Bar.h

@@ -53,7 +53,8 @@ typedef SomeItemSet SomeEnvironment;
 typedef NS_ENUM(long, FooComparisonResult) {
   FooOrderedAscending = -1L,
   FooOrderedSame,
-  FooOrderedDescending
+  FooOrderedDescending,
+  FooOrderedMemberSame,
 };
 
 @interface BarBase

test/Migrator/qualified-replacement.swift

@@ -14,6 +14,11 @@ func foo() {
   _ = Cities.CityKind.Town
   _ = ToplevelType()
   _ = ToplevelType(recordName: "")
+  bar(.orderedSame)
+  bar(.orderedMemberSame)
+  bar(FooComparisonResult.orderedSame)
+  bar(FooComparisonResult.orderedMemberSame)
 }
 
 func foo(_: ToplevelType) {}
+func bar(_ : FooComparisonResult) {}

test/Migrator/qualified-replacement.swift.expected

@@ -14,6 +14,11 @@ func foo() {
   _ = NewCityKind.NewTown
   _ = ToplevelWrapper.internalType()
   _ = ToplevelWrapper.internalType(recordName: "")
+  bar(NewFooComparisonResult.NewFooOrderedSame)
+  bar(.orderedMemberSame)
+  bar(NewFooComparisonResult.NewFooOrderedSame)
+  bar(NewFooComparisonResult.Nested.orderedMemberSame)
 }
 
 func foo(_: ToplevelWrapper.internalType) {}
+func bar(_ : FooComparisonResult) {}