[clang] Don't wrap immediate invocations in ConstantExprs within constexpr initializers (PR #89565)

[via cfe-commits]

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@@ -2554,16 +2554,26 @@ Decl *Parser::ParseDeclarationAfterDeclarator(
   return ParseDeclarationAfterDeclaratorAndAttributes(D, TemplateInfo);
 }
 
+static bool isConstexprVariable(const Decl *D) {
+  if (const VarDecl *Var = dyn_cast_or_null<VarDecl>(D))
+    return Var->isConstexpr();
+
+  return false;
+}
+
 Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
     Declarator &D, const ParsedTemplateInfo &TemplateInfo, ForRangeInit *FRI) {
   // RAII type used to track whether we're inside an initializer.
   struct InitializerScopeRAII {
     Parser &P;
     Declarator &D;
     Decl *ThisDecl;
+    llvm::SaveAndRestore<bool> ConstantContext;
 
     InitializerScopeRAII(Parser &P, Declarator &D, Decl *ThisDecl)
-        : P(P), D(D), ThisDecl(ThisDecl) {
+        : P(P), D(D), ThisDecl(ThisDecl),
+          ConstantContext(P.Actions.isConstantEvaluatedOverride,
+                          isConstexprVariable(ThisDecl)) {
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cor3ntin wrote:

I think we would be better of pushing an actual ExpressionEvaluationContextRecord here

https://github.com/llvm/llvm-project/pull/89565