[clang] [Clang][Sema] Fix an assertion crash when instantiating a nested requirement (PR #213660)

[Younan Zhang via cfe-commits]

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@@ -2832,6 +2832,13 @@ TemplateInstantiator::TransformNestedRequirement(
 
   ASTContext &C = SemaRef.Context;
 
+  if (Req->hasInvalidConstraint()) {
+    if (AlwaysRebuild())
+      return RebuildNestedRequirement(Req->getInvalidConstraintEntity(),
+                                      Req->getConstraintSatisfaction());
+    return Req;
+  }
+
   Expr *Constraint = Req->getConstraintExpr();
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zyn0217 wrote:

Can we instead move line 2842 down to where Constraint is actually used, i.e. to the line after ~2854? We would have less changes then.

https://github.com/llvm/llvm-project/pull/213660