[clang] [clang-tools-extra] [Clang] Retain the angle loci for invented template parameters of constraints (PR #92104)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 created https://github.com/llvm/llvm-project/pull/92104

Clangd uses it to determine whether the argument is within the selection range.

Fixes https://github.com/clangd/clangd/issues/2033

>From d9c0121067162ffb68bc70b9a0a3f10e0b05674c Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Tue, 14 May 2024 19:46:20 +0800
Subject: [PATCH] [Clang] Retain the angle loci for invented template
 parameters of constraints

Clangd uses it to determine whether the argument is within the selection range.

Fixes https://github.com/clangd/clangd/issues/2033
---
 .../clangd/unittests/SelectionTests.cpp             |  5 +++++
 clang/lib/Sema/SemaType.cpp                         |  3 ++-
 clang/test/AST/ast-dump-concepts.cpp                | 13 +++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clangd/unittests/SelectionTests.cpp b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
index db516a1f62a35..706286e22cf74 100644
--- a/clang-tools-extra/clangd/unittests/SelectionTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
@@ -589,6 +589,11 @@ TEST(SelectionTest, CommonAncestor) {
         auto x = [[ns::^C<int>]];
       )cpp",
        "ConceptReference"},
+      {R"cpp(
+        template <typename T, typename K>
+        concept D = true;
+        template <typename T> void g(D<[[^T]]> auto abc) {}
+      )cpp", "TemplateTypeParmTypeLoc"},
   };
 
   for (const Case &C : Cases) {
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index fddc3545ecb61..7eb7cda63a61f 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -3516,7 +3516,8 @@ InventTemplateParameter(TypeProcessingState &state, QualType T,
       // The 'auto' appears in the decl-specifiers; we've not finished forming
       // TypeSourceInfo for it yet.
       TemplateIdAnnotation *TemplateId = D.getDeclSpec().getRepAsTemplateId();
-      TemplateArgumentListInfo TemplateArgsInfo;
+      TemplateArgumentListInfo TemplateArgsInfo(TemplateId->LAngleLoc,
+                                                TemplateId->RAngleLoc);
       bool Invalid = false;
       if (TemplateId->LAngleLoc.isValid()) {
         ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
diff --git a/clang/test/AST/ast-dump-concepts.cpp b/clang/test/AST/ast-dump-concepts.cpp
index 5bb174e3548ed..a5e0673c241ef 100644
--- a/clang/test/AST/ast-dump-concepts.cpp
+++ b/clang/test/AST/ast-dump-concepts.cpp
@@ -107,3 +107,16 @@ auto FooFunc(C auto V) -> C decltype(auto) {
 }
 
 }
+
+namespace constraint_auto_params {
+
+template <class T, class K>
+concept C = true;
+
+template<class T>
+void g(C<T> auto Foo) {}
+
+// CHECK: TemplateTypeParmDecl {{.*}} depth 0 index 1 Foo:auto
+// CHECK-NEXT: `-ConceptSpecializationExpr {{.*}} <col:8, col:11>
+
+}