[Concepts] Add ExpressionEvaluationContexts to instantiation of constraints

Proper ExpressionEvaluationContext were not being entered when instantiating constraint
expressions, which caused assertion failures in certain cases, including bug #44614.

(cherry picked from commit 4d33a8dfcf67e970ea4d150d514b27de02e79aee)

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 8fd7491c45e..92f6e0dc1c9 100755
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1848,6 +1848,8 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(
   // FIXME: Concepts: Do not substitute into constraint expressions
   Expr *TrailingRequiresClause = D->getTrailingRequiresClause();
   if (TrailingRequiresClause) {
+    EnterExpressionEvaluationContext ConstantEvaluated(
+        SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
     ExprResult SubstRC = SemaRef.SubstExpr(TrailingRequiresClause,
                                            TemplateArgs);
     if (SubstRC.isInvalid())
@@ -2186,6 +2188,8 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
   // FIXME: Concepts: Do not substitute into constraint expressions
   Expr *TrailingRequiresClause = D->getTrailingRequiresClause();
   if (TrailingRequiresClause) {
+    EnterExpressionEvaluationContext ConstantEvaluated(
+        SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
     ExprResult SubstRC = SemaRef.SubstExpr(TrailingRequiresClause,
                                            TemplateArgs);
     if (SubstRC.isInvalid())
@@ -2525,6 +2529,8 @@ Decl *TemplateDeclInstantiator::VisitTemplateTypeParmDecl(
     TemplateArgumentListInfo InstArgs;
 
     if (TemplArgInfo) {
+      EnterExpressionEvaluationContext ConstantEvaluated(
+        SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
       InstArgs.setLAngleLoc(TemplArgInfo->LAngleLoc);
       InstArgs.setRAngleLoc(TemplArgInfo->RAngleLoc);
       if (SemaRef.Subst(TemplArgInfo->getTemplateArgs(),
@@ -3729,6 +3735,8 @@ TemplateDeclInstantiator::SubstTemplateParams(TemplateParameterList *L) {
   // checking satisfaction.
   Expr *InstRequiresClause = nullptr;
   if (Expr *E = L->getRequiresClause()) {
+    EnterExpressionEvaluationContext ConstantEvaluated(
+        SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
     ExprResult Res = SemaRef.SubstExpr(E, TemplateArgs);
     if (Res.isInvalid() || !Res.isUsable()) {
       return nullptr;