This revision was automatically updated to reflect the committed changes.
Closed by commit rGb0ed5bea8812: [Clangd] Fixed ExtractVariable for certain 
types of Exprs (authored by SureYeaah).

Changed prior to commit:
  https://reviews.llvm.org/D64717?vs=210803&id=211423#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64717/new/

https://reviews.llvm.org/D64717

Files:
  clang-tools-extra/clangd/refactor/tweaks/ExtractVariable.cpp
  clang-tools-extra/clangd/unittests/TweakTests.cpp

Index: clang-tools-extra/clangd/unittests/TweakTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/TweakTests.cpp
+++ clang-tools-extra/clangd/unittests/TweakTests.cpp
@@ -291,18 +291,23 @@
   const char *Input = "struct ^X { int x; int y; }";
   EXPECT_THAT(getMessage(ID, Input), ::testing::HasSubstr("0 |   int x"));
 }
+
 TEST(TweakTest, ExtractVariable) {
   llvm::StringLiteral ID = "ExtractVariable";
   checkAvailable(ID, R"cpp(
-    int xyz() {
+    int xyz(int a = 1) {
+      struct T {
+        int bar(int a = 1);
+        int z;
+      } t;
       // return statement
-      return [[1]];
+      return [[[[t.b[[a]]r]](t.z)]];
     }
     void f() {
       int a = [[5 +]] [[4 * [[[[xyz]]()]]]];
       // multivariable initialization
       if(1)
-        int x = [[1]], y = [[a]] + 1, a = [[1]], z = a + 1;
+        int x = [[1]], y = [[a + 1]], a = [[1]], z = a + 1;
       // if without else
       if([[1]])
         a = [[1]];
@@ -316,13 +321,13 @@
         a = [[4]];
       else
         a = [[5]];
-      // for loop 
+      // for loop
       for(a = [[1]]; a > [[[[3]] + [[4]]]]; a++)
         a = [[2]];
-      // while 
+      // while
       while(a < [[1]])
-        [[a]]++;
-      // do while 
+        [[a++]];
+      // do while
       do
         a = [[1]];
       while(a < [[3]]);
@@ -332,18 +337,19 @@
   checkNotAvailable(ID, R"cpp(
     template<typename T, typename ...Args>
     struct Test<T, Args...> {
-    Test(const T &v) :val(^) {}
+    Test(const T &v) :val[[(^]]) {}
       T val;
     };
   )cpp");
   checkNotAvailable(ID, R"cpp(
     int xyz(int a = [[1]]) {
-      return 1;
-      class T {
-        T(int a = [[1]]) {};
-        int xyz = [[1]];
-      };
+      struct T {
+        int bar(int a = [[1]]);
+        int z = [[1]];
+      } t;
+      return [[t]].bar([[[[t]].z]]);
     }
+    void v() { return; }
     // function default argument
     void f(int b = [[1]]) {
       // empty selection
@@ -351,17 +357,26 @@
       // void expressions
       auto i = new int, j = new int;
       [[[[delete i]], delete j]];
+      [[v]]();
       // if
       if(1)
         int x = 1, y = a + 1, a = 1, z = [[a + 1]];
       if(int a = 1)
-        if([[a]] == 4)
+        if([[a + 1]] == 4)
           a = [[[[a]] +]] 1;
-      // for loop 
-      for(int a = 1, b = 2, c = 3; [[a]] > [[b + c]]; [[a]]++)
+      // for loop
+      for(int a = 1, b = 2, c = 3; a > [[b + c]]; [[a++]])
         a = [[a + 1]];
-      // lambda 
+      // lambda
       auto lamb = [&[[a]], &[[b]]](int r = [[1]]) {return 1;}
+      // assigment
+      [[a = 5]];
+      // Variable DeclRefExpr
+      a = [[b]];
+      // label statement
+      goto label;
+      label:
+        a = [[1]];
     }
   )cpp");
   // vector of pairs of input and output strings
@@ -397,6 +412,15 @@
                              break;
                        }
                  })cpp"},*/
+          // Macros
+          {R"cpp(#define PLUS(x) x++
+                 void f(int a) {
+                   PLUS([[1+a]]);
+                 })cpp",
+           R"cpp(#define PLUS(x) x++
+                 void f(int a) {
+                   auto dummy = PLUS(1+a); dummy;
+                 })cpp"},
           // ensure InsertionPoint isn't inside a macro
           {R"cpp(#define LOOP(x) while (1) {a = x;}
                  void f(int a) {
@@ -425,25 +449,35 @@
                    auto dummy = 3; if(1)
                     LOOP(5 + dummy)
                  })cpp"},
-          // label and attribute testing
+          // attribute testing
           {R"cpp(void f(int a) {
-                    label: [ [gsl::suppress("type")] ] for (;;) a = [[1]];
+                    [ [gsl::suppress("type")] ] for (;;) a = [[1]];
                  })cpp",
            R"cpp(void f(int a) {
-                    auto dummy = 1; label: [ [gsl::suppress("type")] ] for (;;) a = dummy;
+                    auto dummy = 1; [ [gsl::suppress("type")] ] for (;;) a = dummy;
                  })cpp"},
-          // macro testing
-          {R"cpp(#define PLUS(x) x++
-                 void f(int a) {
-                   PLUS([[a]]);
+          // MemberExpr
+          {R"cpp(class T {
+                   T f() {
+                     return [[T().f()]].f();
+                   }
+                 };)cpp",
+           R"cpp(class T {
+                   T f() {
+                     auto dummy = T().f(); return dummy.f();
+                   }
+                 };)cpp"},
+          // Function DeclRefExpr
+          {R"cpp(int f() {
+                   return [[f]]();
                  })cpp",
-           R"cpp(#define PLUS(x) x++
-                 void f(int a) {
-                   auto dummy = a; PLUS(dummy);
+           R"cpp(int f() {
+                   auto dummy = f(); return dummy;
                  })cpp"},
-          // FIXME: Doesn't work correctly for \[\[clang::uninitialized\]\] int
-          // b = [[1]]; since the attr is inside the DeclStmt and the bounds of
-          // DeclStmt don't cover the attribute
+          
+          // FIXME: Wrong result for \[\[clang::uninitialized\]\] int b = [[1]];
+          // since the attr is inside the DeclStmt and the bounds of
+          // DeclStmt don't cover the attribute.
       };
   for (const auto &IO : InputOutputs) {
     checkTransform(ID, IO.first, IO.second);
Index: clang-tools-extra/clangd/refactor/tweaks/ExtractVariable.cpp
===================================================================
--- clang-tools-extra/clangd/refactor/tweaks/ExtractVariable.cpp
+++ clang-tools-extra/clangd/refactor/tweaks/ExtractVariable.cpp
@@ -13,6 +13,7 @@
 #include "refactor/Tweak.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
 #include "clang/AST/OperationKinds.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/Stmt.h"
@@ -77,29 +78,15 @@
   return Visitor.ReferencedDecls;
 }
 
-// An expr is not extractable if it's null or an expression of type void
-// FIXME: Ignore assignment (a = 1) Expr since it is extracted as dummy = a =
-static bool isExtractableExpr(const clang::Expr *Expr) {
-  if (Expr) {
-    const Type *ExprType = Expr->getType().getTypePtrOrNull();
-    // FIXME: check if we need to cover any other types
-    if (ExprType)
-      return !ExprType->isVoidType();
-  }
-  return false;
-}
-
 ExtractionContext::ExtractionContext(const SelectionTree::Node *Node,
                                      const SourceManager &SM,
                                      const ASTContext &Ctx)
     : ExprNode(Node), SM(SM), Ctx(Ctx) {
   Expr = Node->ASTNode.get<clang::Expr>();
-  if (isExtractableExpr(Expr)) {
-    ReferencedDecls = computeReferencedDecls(Expr);
-    InsertionPoint = computeInsertionPoint();
-    if (InsertionPoint)
-      Extractable = true;
-  }
+  ReferencedDecls = computeReferencedDecls(Expr);
+  InsertionPoint = computeInsertionPoint();
+  if (InsertionPoint)
+    Extractable = true;
 }
 
 // checks whether extracting before InsertionPoint will take a
@@ -121,9 +108,9 @@
 // the current Stmt. We ALWAYS insert before a Stmt whose parent is a
 // CompoundStmt
 //
-
-// FIXME: Extraction from switch and case statements
+// FIXME: Extraction from label, switch and case statements
 // FIXME: Doens't work for FoldExpr
+// FIXME: Ensure extraction from loops doesn't change semantics.
 const clang::Stmt *ExtractionContext::computeInsertionPoint() const {
   // returns true if we can extract before InsertionPoint
   auto CanExtractOutside =
@@ -141,8 +128,7 @@
       return isa<AttributedStmt>(Stmt) || isa<CompoundStmt>(Stmt) ||
              isa<CXXForRangeStmt>(Stmt) || isa<DeclStmt>(Stmt) ||
              isa<DoStmt>(Stmt) || isa<ForStmt>(Stmt) || isa<IfStmt>(Stmt) ||
-             isa<LabelStmt>(Stmt) || isa<ReturnStmt>(Stmt) ||
-             isa<WhileStmt>(Stmt);
+             isa<ReturnStmt>(Stmt) || isa<WhileStmt>(Stmt);
     }
     if (InsertionPoint->ASTNode.get<VarDecl>())
       return true;
@@ -209,6 +195,9 @@
     return "Extract subexpression to variable";
   }
   Intent intent() const override { return Refactor; }
+  // Compute the extraction context for the Selection
+  bool computeExtractionContext(const SelectionTree::Node *N,
+                                const SourceManager &SM, const ASTContext &Ctx);
 
 private:
   // the expression to extract
@@ -216,14 +205,13 @@
 };
 REGISTER_TWEAK(ExtractVariable)
 bool ExtractVariable::prepare(const Selection &Inputs) {
+  // we don't trigger on empty selections for now
+  if (Inputs.SelectionBegin == Inputs.SelectionEnd)
+    return false;
   const ASTContext &Ctx = Inputs.AST.getASTContext();
   const SourceManager &SM = Inputs.AST.getSourceManager();
   const SelectionTree::Node *N = Inputs.ASTSelection.commonAncestor();
-  // we don't trigger on empty selections for now
-  if (!N || Inputs.SelectionBegin == Inputs.SelectionEnd)
-    return false;
-  Target = llvm::make_unique<ExtractionContext>(N, SM, Ctx);
-  return Target->isExtractable();
+  return computeExtractionContext(N, SM, Ctx);
 }
 
 Expected<Tweak::Effect> ExtractVariable::apply(const Selection &Inputs) {
@@ -239,6 +227,75 @@
   return Effect::applyEdit(Result);
 }
 
+// Find the CallExpr whose callee is an ancestor of the DeclRef
+const SelectionTree::Node *getCallExpr(const SelectionTree::Node *DeclRef) {
+  // we maintain a stack of all exprs encountered while traversing the
+  // selectiontree because the callee of the callexpr can be an ancestor of the
+  // DeclRef. e.g. Callee can be an ImplicitCastExpr.
+  std::vector<const clang::Expr *> ExprStack;
+  for (auto *CurNode = DeclRef; CurNode; CurNode = CurNode->Parent) {
+    const Expr *CurExpr = CurNode->ASTNode.get<Expr>();
+    if (const CallExpr *CallPar = CurNode->ASTNode.get<CallExpr>()) {
+      // check whether the callee of the callexpr is present in Expr stack.
+      if (std::find(ExprStack.begin(), ExprStack.end(), CallPar->getCallee()) !=
+          ExprStack.end())
+        return CurNode;
+      return nullptr;
+    }
+    ExprStack.push_back(CurExpr);
+  }
+  return nullptr;
+}
+
+// check if Expr can be assigned to a variable i.e. is non-void type
+bool canBeAssigned(const SelectionTree::Node *ExprNode) {
+  const clang::Expr *Expr = ExprNode->ASTNode.get<clang::Expr>();
+  if (const Type *ExprType = Expr->getType().getTypePtrOrNull())
+    // FIXME: check if we need to cover any other types
+    return !ExprType->isVoidType();
+  return true;
+}
+
+// Find the node that will form our ExtractionContext.
+// We don't want to trigger for assignment expressions and variable/field
+// DeclRefs. For function/member function, we want to extract the entire
+// function call.
+bool ExtractVariable::computeExtractionContext(const SelectionTree::Node *N,
+                                               const SourceManager &SM,
+                                               const ASTContext &Ctx) {
+  if (!N)
+    return false;
+  const clang::Expr *SelectedExpr = N->ASTNode.get<clang::Expr>();
+  const SelectionTree::Node *TargetNode = N;
+  if (!SelectedExpr)
+    return false;
+  // Extracting Exprs like a = 1 gives dummy = a = 1 which isn't useful.
+  if (const BinaryOperator *BinOpExpr =
+          dyn_cast_or_null<BinaryOperator>(SelectedExpr)) {
+    if (BinOpExpr->getOpcode() == BinaryOperatorKind::BO_Assign)
+      return false;
+  }
+  // For function and member function DeclRefs, we look for a parent that is a
+  // CallExpr
+  if (const DeclRefExpr *DeclRef =
+          dyn_cast_or_null<DeclRefExpr>(SelectedExpr)) {
+    // Extracting just a variable isn't that useful.
+    if (!isa<FunctionDecl>(DeclRef->getDecl()))
+      return false;
+    TargetNode = getCallExpr(N);
+  }
+  if (const MemberExpr *Member = dyn_cast_or_null<MemberExpr>(SelectedExpr)) {
+    // Extracting just a field member isn't that useful.
+    if (!isa<CXXMethodDecl>(Member->getMemberDecl()))
+      return false;
+    TargetNode = getCallExpr(N);
+  }
+  if (!TargetNode || !canBeAssigned(TargetNode))
+    return false;
+  Target = llvm::make_unique<ExtractionContext>(TargetNode, SM, Ctx);
+  return Target->isExtractable();
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang
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