[clang] [Clang][Parser] Remove the concept from the DeclContext if the definition is invalid (PR #111179)

[Younan Zhang via cfe-commits]

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@@ -337,6 +343,8 @@ Parser::ParseConceptDefinition(const ParsedTemplateInfo &TemplateInfo,
   ExprResult ConstraintExprResult =
       Actions.CorrectDelayedTyposInExpr(ParseConstraintExpression());
   if (ConstraintExprResult.isInvalid()) {
+    if (AddedToScope)
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zyn0217 wrote:

Oh NVM, I see your point:
`PushOnScopeChains()` is hinged on `Previous.empty()`, so I'm afraid we need the flag, otherwise we can definitely do away with the flag

https://github.com/llvm/llvm-project/pull/111179