[clang] [Clang] Fix a concept subsumption bug when template depths are adjusted (PR #186735)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Younan Zhang (zyn0217)

<details>
<summary>Changes</summary>

We cannot reuse the cached normalization results if any template depth adjustments (in subsumption checking) are involved.

Fixes https://github.com/llvm/llvm-project/issues/186624

I hope this can be backported without breaking ABI

---
Full diff: https://github.com/llvm/llvm-project/pull/186735.diff


3 Files Affected:

- (modified) clang/include/clang/Sema/SemaConcept.h (+2-1) 
- (modified) clang/lib/Sema/SemaConcept.cpp (+7-4) 
- (modified) clang/test/SemaTemplate/concepts.cpp (+19) 


``````````diff
diff --git a/clang/include/clang/Sema/SemaConcept.h b/clang/include/clang/Sema/SemaConcept.h
index bdd997b18cb08..e6644f1bd1bee 100644
--- a/clang/include/clang/Sema/SemaConcept.h
+++ b/clang/include/clang/Sema/SemaConcept.h
@@ -431,7 +431,8 @@ class SubsumptionChecker {
   std::optional<bool> Subsumes(const NamedDecl *DP,
                                ArrayRef<AssociatedConstraint> P,
                                const NamedDecl *DQ,
-                               ArrayRef<AssociatedConstraint> Q);
+                               ArrayRef<AssociatedConstraint> Q,
+                               bool DepthAdjusted);
 
   bool Subsumes(const NormalizedConstraint *P, const NormalizedConstraint *Q);
 
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 38791940247cb..16cbec22c823b 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -2544,7 +2544,8 @@ bool Sema::IsAtLeastAsConstrained(const NamedDecl *D1,
   }
 
   SubsumptionChecker SC(*this);
-  std::optional<bool> Subsumes = SC.Subsumes(D1, AC1, D2, AC2);
+  std::optional<bool> Subsumes =
+      SC.Subsumes(D1, AC1, D2, AC2, /*DepthAdjusted=*/Depth1 != Depth2);
   if (!Subsumes) {
     // Normalization failed
     return true;
@@ -2778,14 +2779,16 @@ void SubsumptionChecker::AddUniqueClauseToFormula(Formula &F, Clause C) {
 
 std::optional<bool> SubsumptionChecker::Subsumes(
     const NamedDecl *DP, ArrayRef<AssociatedConstraint> P, const NamedDecl *DQ,
-    ArrayRef<AssociatedConstraint> Q) {
+    ArrayRef<AssociatedConstraint> Q, bool DepthAdjusted) {
   const NormalizedConstraint *PNormalized =
-      SemaRef.getNormalizedAssociatedConstraints(DP, P);
+      SemaRef.getNormalizedAssociatedConstraints(DepthAdjusted ? nullptr : DP,
+                                                 P);
   if (!PNormalized)
     return std::nullopt;
 
   const NormalizedConstraint *QNormalized =
-      SemaRef.getNormalizedAssociatedConstraints(DQ, Q);
+      SemaRef.getNormalizedAssociatedConstraints(DepthAdjusted ? nullptr : DQ,
+                                                 Q);
   if (!QNormalized)
     return std::nullopt;
 
diff --git a/clang/test/SemaTemplate/concepts.cpp b/clang/test/SemaTemplate/concepts.cpp
index 1d2ada3e0a398..628499bebea83 100644
--- a/clang/test/SemaTemplate/concepts.cpp
+++ b/clang/test/SemaTemplate/concepts.cpp
@@ -1659,6 +1659,25 @@ void foo() { call(""); }
 
 }
 
+namespace GH186624 {
+
+template <class T>
+concept C = __is_unsigned(T);
+
+template <C T>
+struct encoder_interface {};
+
+template <template <C> class CodecInterface, C T>
+CodecInterface<T>* create_codec() {
+  return nullptr;
+}
+
+encoder_interface<unsigned>* create_encoder() {
+  return create_codec<encoder_interface, unsigned>();
+}
+
+}
+
 namespace GH170856 {
 
 template <unsigned N, unsigned M> struct symbol_text {

``````````

</details>


https://github.com/llvm/llvm-project/pull/186735