[clangd] Don't add inlay hints on std::move/forward

[upsj]

Summary

This removes parameter inlay hints from a few builtin functions like std::move/std::forward

[nridge]

Thanks!

clang-tools-extra/clangd/InlayHints.cpp

 //===--- InlayHints.cpp ------------------------------------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 #include "InlayHints.h"
 #include "AST.h"
 #include "Config.h"
 #include "HeuristicResolver.h"
 #include "ParsedAST.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclarationName.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Basic/Builtins.h"
 #include "clang/Basic/SourceManager.h"
 #include "llvm/ADT/ScopeExit.h"
 
 namespace clang {
 namespace clangd {
 namespace {
 
 // For now, inlay hints are always anchored at the left or right of their range.
void processCall(SourceLocation Anchor, const FunctionDecl *Callee,
     // Don't show hints for variadic parameters.
     size_t FixedParamCount = getFixedParamCount(Callee);
     size_t ArgCount = std::min(FixedParamCount, Args.size());
     auto Params = Callee->parameters();
 
     NameVec ParameterNames = chooseParameterNames(Callee, ArgCount);
 
     // Exclude setters (i.e. functions with one argument whose name begins with
-    // "set"), as their parameter name is also not likely to be interesting.
-    if (isSetter(Callee, ParameterNames))
+    // "set"), and builtins like std::move/forward/... as their parameter name
+    // is also not likely to be interesting.
+    if (isSetter(Callee, ParameterNames) || isSimpleBuiltin(Callee))
       return;
 
     for (size_t I = 0; I < ArgCount; ++I) {
       StringRef Name = ParameterNames[I];
       bool NameHint = shouldHintName(Args[I], Name);
       bool ReferenceHint = shouldHintReference(Params[I]);
 
       if (NameHint || ReferenceHint) {
static bool isSetter(const FunctionDecl *Callee, const NameVec &ParamNames) {
     // and functions don't, e.g.
     //   void setExceptionHandler(EHFunc exception_handler);
     // We could improve this by replacing `equals_insensitive` with some
     // `sloppy_equals` which ignores case and also skips underscores.
     StringRef WhatItIsSetting = Name.substr(3).ltrim("_");
     return WhatItIsSetting.equals_insensitive(ParamNames[0]);
   }
 
+  // Checks if the callee is one of the builtins
+  // addressof, as_const, forward, move(_if_noexcept)
+  static bool isSimpleBuiltin(const FunctionDecl *Callee) {
+    switch (Callee->getBuiltinID()) {
+    case Builtin::BIaddressof:
+    case Builtin::BIas_const:
+    case Builtin::BIforward:
+    case Builtin::BImove:
+    case Builtin::BImove_if_noexcept:
+      return true;
+    default:
+      return false;
+    }
+  }
+
   bool shouldHintName(const Expr *Arg, StringRef ParamName) {
     if (ParamName.empty())
       return false;
 
     // If the argument expression is a single name and it matches the
     // parameter name exactly, omit the name hint.
     if (ParamName == getSpelledIdentifier(Arg))
       return false;

clang-tools-extra/clangd/unittests/InlayHintTests.cpp

void bar() {
       // FIXME: Ideally we'd want to omit this.
       s.setTimeoutMillis($timeout_millis[[120]]);
     }
   )cpp",
                        ExpectedHint{"timeoutMillis: ", "timeoutMillis"},
                        ExpectedHint{"timeout_millis: ", "timeout_millis"});
 }
 
+TEST(ParameterHints, BuiltinFunctions) {
+  // This prototype of std::forward is sufficient for clang to recognize it
+  assertParameterHints(R"cpp(
+    namespace std { template <typename T> T&& forward(T&); }
+    void foo() {
+      int i;
+      std::forward(i);
+    }
+  )cpp");
+}
+
 TEST(ParameterHints, IncludeAtNonGlobalScope) {
   Annotations FooInc(R"cpp(
     void bar() { foo(42); }
   )cpp");
   Annotations FooCC(R"cpp(
     struct S {
       void foo(int param);
       #include "foo.inc"