[clang] [Clang] Fix the order of addInstantiatedParameters in LambdaScopeForCallOperatorInstantiationRAII (PR #97215)

[Yupei Liu via cfe-commits]

https://github.com/LYP951018 updated https://github.com/llvm/llvm-project/pull/97215

>From a997ae70f86230200b1082c9bdc0bdf56e30b7c4 Mon Sep 17 00:00:00 2001
From: letrec <liuyupei951018 at hotmail.com>
Date: Sun, 30 Jun 2024 21:03:23 +0800
Subject: [PATCH 1/2] Fix the order of addInstantiatedParameters in
 LambdaScopeForCallOperatorInstantiationRAII.

---
 clang/lib/Sema/SemaLambda.cpp               | 37 +++++++++++++--------
 clang/test/SemaTemplate/concepts-lambda.cpp | 14 ++++++++
 2 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index ca9c7cb9faadf..b6344f53861f4 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -2379,23 +2379,32 @@ Sema::LambdaScopeForCallOperatorInstantiationRAII::
 
   SemaRef.RebuildLambdaScopeInfo(cast<CXXMethodDecl>(FD));
 
-  FunctionDecl *Pattern = getPatternFunctionDecl(FD);
-  if (Pattern) {
-    SemaRef.addInstantiatedCapturesToScope(FD, Pattern, Scope, MLTAL);
+  FunctionDecl *FDPattern = getPatternFunctionDecl(FD);
+  if (!FDPattern)
+    return;
 
-    FunctionDecl *ParentFD = FD;
-    while (ShouldAddDeclsFromParentScope) {
+  SemaRef.addInstantiatedCapturesToScope(FD, FDPattern, Scope, MLTAL);
 
-      ParentFD =
-          dyn_cast<FunctionDecl>(getLambdaAwareParentOfDeclContext(ParentFD));
-      Pattern =
-          dyn_cast<FunctionDecl>(getLambdaAwareParentOfDeclContext(Pattern));
+  if (!ShouldAddDeclsFromParentScope)
+    return;
 
-      if (!ParentFD || !Pattern)
-        break;
+  llvm::SmallVector<std::pair<FunctionDecl *, FunctionDecl *>, 4>
+      ParentInstantiations;
+  std::pair<FunctionDecl *, FunctionDecl *> Current = {FDPattern, FD};
+  while (true) {
+    Current.first = dyn_cast<FunctionDecl>(
+        getLambdaAwareParentOfDeclContext(Current.first));
+    Current.second = dyn_cast<FunctionDecl>(
+        getLambdaAwareParentOfDeclContext(Current.second));
 
-      SemaRef.addInstantiatedParametersToScope(ParentFD, Pattern, Scope, MLTAL);
-      SemaRef.addInstantiatedLocalVarsToScope(ParentFD, Pattern, Scope);
-    }
+    if (!Current.first || !Current.second)
+      break;
+
+    ParentInstantiations.push_back(Current);
+  }
+
+  for (const auto &[Pattern, Inst] : llvm::reverse(ParentInstantiations)) {
+    SemaRef.addInstantiatedParametersToScope(Inst, Pattern, Scope, MLTAL);
+    SemaRef.addInstantiatedLocalVarsToScope(Inst, Pattern, Scope);
   }
 }
diff --git a/clang/test/SemaTemplate/concepts-lambda.cpp b/clang/test/SemaTemplate/concepts-lambda.cpp
index 280be71284f97..252ef08549a48 100644
--- a/clang/test/SemaTemplate/concepts-lambda.cpp
+++ b/clang/test/SemaTemplate/concepts-lambda.cpp
@@ -237,3 +237,17 @@ concept D = []<C T = int>() { return true; }();
 D auto x = 0;
 
 } // namespace GH93821
+
+namespace dependent_param_concept {
+template <typename... Ts> void sink(Ts...) {}
+void dependent_param() {
+  auto L = [](auto... x) {
+    return [](decltype(x)... y) {
+      return [](int z)
+        requires requires { sink(y..., z); }
+      {};
+    };
+  };
+  L(0, 1)(1, 2)(1);
+}
+} // namespace dependent_param_concept

>From 85730ed7829d0a327e9b9ba9efa95e0b6dce9761 Mon Sep 17 00:00:00 2001
From: letrec <liuyupei951018 at hotmail.com>
Date: Sun, 7 Jul 2024 02:27:53 +0800
Subject: [PATCH 2/2] CR comments

---
 clang/docs/ReleaseNotes.rst   |  1 +
 clang/lib/Sema/SemaLambda.cpp | 25 +++++++++++++++----------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c720e47dbe35b..8f6c8b98b1322 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -929,6 +929,7 @@ Bug Fixes to C++ Support
 - Fix a crash caused by improper use of ``__array_extent``. (#GH80474)
 - Fixed several bugs in capturing variables within unevaluated contexts. (#GH63845), (#GH67260), (#GH69307),
   (#GH88081), (#GH89496), (#GH90669) and (#GH91633).
+- Fixed a crash in constraint instantiation under nested lambdas with dependent parameters.
 - Fixed handling of brace ellison when building deduction guides. (#GH64625), (#GH83368).
 - Clang now instantiates local constexpr functions eagerly for constant evaluators. (#GH35052), (#GH94849)
 - Fixed a failed assertion when attempting to convert an integer representing the difference
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index b6344f53861f4..e461827be1e9d 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -2390,21 +2390,26 @@ Sema::LambdaScopeForCallOperatorInstantiationRAII::
 
   llvm::SmallVector<std::pair<FunctionDecl *, FunctionDecl *>, 4>
       ParentInstantiations;
-  std::pair<FunctionDecl *, FunctionDecl *> Current = {FDPattern, FD};
   while (true) {
-    Current.first = dyn_cast<FunctionDecl>(
-        getLambdaAwareParentOfDeclContext(Current.first));
-    Current.second = dyn_cast<FunctionDecl>(
-        getLambdaAwareParentOfDeclContext(Current.second));
+    FDPattern =
+        dyn_cast<FunctionDecl>(getLambdaAwareParentOfDeclContext(FDPattern));
+    FD = dyn_cast<FunctionDecl>(getLambdaAwareParentOfDeclContext(FD));
 
-    if (!Current.first || !Current.second)
+    if (!FDPattern || !FD)
       break;
 
-    ParentInstantiations.push_back(Current);
+    ParentInstantiations.emplace_back(FDPattern, FD);
   }
 
-  for (const auto &[Pattern, Inst] : llvm::reverse(ParentInstantiations)) {
-    SemaRef.addInstantiatedParametersToScope(Inst, Pattern, Scope, MLTAL);
-    SemaRef.addInstantiatedLocalVarsToScope(Inst, Pattern, Scope);
+  // Add instantiated parameters and local vars to scopes, starting from the
+  // outermost lambda to the innermost lambda. This ordering ensures that
+  // parameters in inner lambdas can correctly depend on those defined
+  // in outer lambdas, e.g. auto L = [](auto... x) {
+  //   return [](decltype(x)... y) { }; // `y` depends on `x`
+  // };
+
+  for (const auto &[FDPattern, FD] : llvm::reverse(ParentInstantiations)) {
+    SemaRef.addInstantiatedParametersToScope(FD, FDPattern, Scope, MLTAL);
+    SemaRef.addInstantiatedLocalVarsToScope(FD, FDPattern, Scope);
   }
 }