[clangd] fix extract function tweak signature spelling out lambda types

[5chmidti]

Summary

Fixes the signature of the extracted function when the signature contains a lambda.
Previously spelled out the type (i.e. loc, ...) of the lambda, now specifies auto.

[5chmidti]

Nvmd, Wrapped</*lambda type*/> won't work. I'll look into this some more.

clang-tools-extra/clangd/AST.cpp

public:
     }
 
   private:
     const DeclContext *CurContext;
   };
   PrintCB PCB(&CurContext);
   PP.Callbacks = &PCB;
 
+  if (const auto *const RDecl = QT->getAsCXXRecordDecl();
+      RDecl && RDecl->isLambda()) {
+    return "auto";
+  }
+
   QT.print(OS, PP, Placeholder);
   return OS.str();
 }
 
 bool hasReservedName(const Decl &D) {
   if (const auto *ND = llvm::dyn_cast<NamedDecl>(&D))
     if (const auto *II = ND->getIdentifier())
       return isReservedName(II->getName());

clang-tools-extra/clangd/unittests/tweaks/ExtractFunctionTests.cpp

F (extracted();)
   EXPECT_EQ(apply("void f(int a = [[1]]);"), "unavailable");
   // Don't extract if we select the entire function body (CompoundStmt).
   std::string CompoundFailInput = R"cpp(
     void f() [[{
       int a;
     }]]
   )cpp";
   EXPECT_EQ(apply(CompoundFailInput), "unavailable");
+
+  std::string LambdaInput = R"cpp(
+auto bar() {
+  int x = 10;
+  auto lambda = [x]() { return x; };
+  [[int y = 42;
+  int z = lambda();]]
+
+  return lambda();
+}
+  )cpp";
+
+  std::string LambdaOutput = R"cpp(
+void extracted(auto &lambda) {
+int y = 42;
+  int z = lambda();
+}
+auto bar() {
+  int x = 10;
+  auto lambda = [x]() { return x; };
+  extracted(lambda);
+
+  return lambda();
+}
+  )cpp";
+  EXPECT_EQ(apply(LambdaInput), LambdaOutput);
 }
 
 TEST_F(ExtractFunctionTest, DifferentHeaderSourceTest) {
   Header = R"cpp(
     class SomeClass {
       void f();
     };
   )cpp";

clang-tools-extra/docs/ReleaseNotes.rst

 ^^^^^^^^^^^^^^^^
 
 Objective-C
 ^^^^^^^^^^^
 
 Miscellaneous
 ^^^^^^^^^^^^^
 
+- Fixed extracted function signatures spelling out lambda types.
+
 Improvements to clang-doc
 -------------------------
 
 - The default executor was changed to standalone to match other tools.
 
 Improvements to clang-query
 ---------------------------