[clang-tools-extra] [clangd] Handle dependent call to function with explicit object parameter in InlayHintVisitor (PR #201264)

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<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clangd

@llvm/pr-subscribers-clang-tools-extra

Author: Nathan Ridge (HighCommander4)

<details>
<summary>Changes</summary>

Dependent calls do not yet have the implicit object argument preprended to the CallExpr's argument list, so the first argument should not be expected to be present and dropped in this case.

Fixes https://github.com/llvm/llvm-project/issues/198588

---
Full diff: https://github.com/llvm/llvm-project/pull/201264.diff


2 Files Affected:

- (modified) clang-tools-extra/clangd/InlayHints.cpp (+2-1) 
- (modified) clang-tools-extra/clangd/unittests/InlayHintTests.cpp (+15) 


``````````diff
diff --git a/clang-tools-extra/clangd/InlayHints.cpp b/clang-tools-extra/clangd/InlayHints.cpp
index 951177e3546f2..5bae4cc040210 100644
--- a/clang-tools-extra/clangd/InlayHints.cpp
+++ b/clang-tools-extra/clangd/InlayHints.cpp
@@ -492,7 +492,8 @@ class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
     // either.
     if (const CXXMethodDecl *Method =
             dyn_cast_or_null<CXXMethodDecl>(Callee.Decl))
-      if (IsFunctor || Method->hasCXXExplicitFunctionObjectParameter())
+      if (IsFunctor || (!E->isTypeDependent() &&
+                        Method->hasCXXExplicitFunctionObjectParameter()))
         Args = Args.drop_front(1);
     processCall(Callee, E->getRParenLoc(), Args);
     return true;
diff --git a/clang-tools-extra/clangd/unittests/InlayHintTests.cpp b/clang-tools-extra/clangd/unittests/InlayHintTests.cpp
index 5552aa178a354..b90f44d102018 100644
--- a/clang-tools-extra/clangd/unittests/InlayHintTests.cpp
+++ b/clang-tools-extra/clangd/unittests/InlayHintTests.cpp
@@ -890,6 +890,21 @@ TEST(ParameterHints, DeducingThis) {
                        ExpectedHint{"Param: ", "3"}, ExpectedHint{"C: ", "4"});
 }
 
+TEST(ParameterHints, DependentDeducingThis) {
+  assertParameterHints(R"cpp(
+   template <typename T>
+   struct S {
+      void f1(this S& obj);
+      void f2(this S& obj, int x, int y);
+      void g(S s) {
+        s.f1();  // no crash
+        s.f2($x[[42]], $y[[43]]);
+      }
+    };
+  )cpp",
+                       ExpectedHint{"x: ", "x"}, ExpectedHint{"y: ", "y"});
+}
+
 TEST(ParameterHints, Macros) {
   // Handling of macros depends on where the call's argument list comes from.
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/201264