1 files changed, 56 insertions, 23 deletions

diff --git a/contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp b/contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp
index df6b40999e64..7f20413c104e 100644
--- a/contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -35,7 +35,6 @@
 #include "clang/Sema/Template.h"
 #include "clang/Sema/TemplateDeduction.h"
 #include "clang/Sema/TemplateInstCallback.h"
-#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/TimeProfiler.h"
@@ -345,15 +344,26 @@ MultiLevelTemplateArgumentList Sema::getTemplateInstantiationArgs(
 
   using namespace TemplateInstArgsHelpers;
   const Decl *CurDecl = ND;
+
+  if (!CurDecl)
+    CurDecl = Decl::castFromDeclContext(DC);
+
   if (Innermost) {
     Result.addOuterTemplateArguments(const_cast<NamedDecl *>(ND),
                                      Innermost->asArray(), Final);
-    CurDecl = Response::UseNextDecl(ND).NextDecl;
+    // Populate placeholder template arguments for TemplateTemplateParmDecls.
+    // This is essential for the case e.g.
+    //
+    // template <class> concept Concept = false;
+    // template <template <Concept C> class T> void foo(T<int>)
+    //
+    // where parameter C has a depth of 1 but the substituting argument `int`
+    // has a depth of 0.
+    if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(CurDecl))
+      HandleDefaultTempArgIntoTempTempParam(TTP, Result);
+    CurDecl = Response::UseNextDecl(CurDecl).NextDecl;
   }
 
-  if (!ND)
-    CurDecl = Decl::castFromDeclContext(DC);
-
   while (!CurDecl->isFileContextDecl()) {
     Response R;
     if (const auto *VarTemplSpec =
@@ -381,10 +391,8 @@ MultiLevelTemplateArgumentList Sema::getTemplateInstantiationArgs(
       R = Response::ChangeDecl(CTD->getLexicalDeclContext());
     } else if (!isa<DeclContext>(CurDecl)) {
       R = Response::DontClearRelativeToPrimaryNextDecl(CurDecl);
-      if (CurDecl->getDeclContext()->isTranslationUnit()) {
-        if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(CurDecl)) {
-          R = HandleDefaultTempArgIntoTempTempParam(TTP, Result);
-        }
+      if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(CurDecl)) {
+        R = HandleDefaultTempArgIntoTempTempParam(TTP, Result);
       }
     } else {
       R = HandleGenericDeclContext(CurDecl);
@@ -1142,8 +1150,7 @@ std::optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
     case CodeSynthesisContext::DeducedTemplateArgumentSubstitution:
       // We're either substituting explicitly-specified template arguments,
       // deduced template arguments. SFINAE applies unless we are in a lambda
-      // expression, see [temp.deduct]p9.
-      [[fallthrough]];
+      // body, see [temp.deduct]p9.
     case CodeSynthesisContext::ConstraintSubstitution:
     case CodeSynthesisContext::RequirementInstantiation:
     case CodeSynthesisContext::RequirementParameterInstantiation:
@@ -1190,6 +1197,7 @@ namespace {
     const MultiLevelTemplateArgumentList &TemplateArgs;
     SourceLocation Loc;
     DeclarationName Entity;
+    // Whether to evaluate the C++20 constraints or simply substitute into them.
     bool EvaluateConstraints = true;
 
   public:
@@ -1444,13 +1452,6 @@ namespace {
       LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
       Sema::ConstraintEvalRAII<TemplateInstantiator> RAII(*this);
 
-      Sema::CodeSynthesisContext C;
-      C.Kind = clang::Sema::CodeSynthesisContext::LambdaExpressionSubstitution;
-      C.PointOfInstantiation = E->getBeginLoc();
-      SemaRef.pushCodeSynthesisContext(C);
-      auto PopCtx =
-          llvm::make_scope_exit([this] { SemaRef.popCodeSynthesisContext(); });
-
       ExprResult Result = inherited::TransformLambdaExpr(E);
       if (Result.isInvalid())
         return Result;
@@ -1478,6 +1479,23 @@ namespace {
       return Result;
     }
 
+    StmtResult TransformLambdaBody(LambdaExpr *E, Stmt *Body) {
+      // Currently, we instantiate the body when instantiating the lambda
+      // expression. However, `EvaluateConstraints` is disabled during the
+      // instantiation of the lambda expression, causing the instantiation
+      // failure of the return type requirement in the body. If p0588r1 is fully
+      // implemented, the body will be lazily instantiated, and this problem
+      // will not occur. Here, `EvaluateConstraints` is temporarily set to
+      // `true` to temporarily fix this issue.
+      // FIXME: This temporary fix can be removed after fully implementing
+      // p0588r1.
+      bool Prev = EvaluateConstraints;
+      EvaluateConstraints = true;
+      StmtResult Stmt = inherited::TransformLambdaBody(E, Body);
+      EvaluateConstraints = Prev;
+      return Stmt;
+    }
+
     ExprResult TransformRequiresExpr(RequiresExpr *E) {
       LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
       ExprResult TransReq = inherited::TransformRequiresExpr(E);
@@ -1630,9 +1648,7 @@ bool TemplateInstantiator::TransformExceptionSpec(
     SourceLocation Loc, FunctionProtoType::ExceptionSpecInfo &ESI,
     SmallVectorImpl<QualType> &Exceptions, bool &Changed) {
   if (ESI.Type == EST_Uninstantiated) {
-    ESI.NoexceptExpr = cast<FunctionProtoType>(ESI.SourceTemplate->getType())
-                           ->getNoexceptExpr();
-    ESI.Type = EST_DependentNoexcept;
+    ESI.instantiate();
     Changed = true;
   }
   return inherited::TransformExceptionSpec(Loc, ESI, Exceptions, Changed);
@@ -2499,6 +2515,17 @@ TemplateInstantiator::TransformNestedRequirement(
       Req->getConstraintExpr()->getBeginLoc(), Req,
       Sema::InstantiatingTemplate::ConstraintsCheck{},
       Req->getConstraintExpr()->getSourceRange());
+  if (!getEvaluateConstraints()) {
+    ExprResult TransConstraint = TransformExpr(Req->getConstraintExpr());
+    if (TransConstraint.isInvalid() || !TransConstraint.get())
+      return nullptr;
+    if (TransConstraint.get()->isInstantiationDependent())
+      return new (SemaRef.Context)
+          concepts::NestedRequirement(TransConstraint.get());
+    ConstraintSatisfaction Satisfaction;
+    return new (SemaRef.Context) concepts::NestedRequirement(
+        SemaRef.Context, TransConstraint.get(), Satisfaction);
+  }
 
   ExprResult TransConstraint;
   ConstraintSatisfaction Satisfaction;
@@ -4093,13 +4120,19 @@ Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
 ExprResult
 Sema::SubstConstraintExpr(Expr *E,
                           const MultiLevelTemplateArgumentList &TemplateArgs) {
+  // FIXME: should call SubstExpr directly if this function is equivalent or
+  //        should it be different?
+  return SubstExpr(E, TemplateArgs);
+}
+
+ExprResult Sema::SubstConstraintExprWithoutSatisfaction(
+    Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
   if (!E)
     return E;
 
-  // This is where we need to make sure we 'know' constraint checking needs to
-  // happen.
   TemplateInstantiator Instantiator(*this, TemplateArgs, SourceLocation(),
                                     DeclarationName());
+  Instantiator.setEvaluateConstraints(false);
   return Instantiator.TransformExpr(E);
 }