[clang] [clang] Fix TemplateInstantiator crash transforming loop hint argument (PR #172289)

[Bruno De Fraine via cfe-commits]

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@@ -8,3 +8,28 @@ template <int Unroll> void foo() {
   #pragma GCC unroll Unroll
   for (int i = 0; i < Unroll; ++i);
 }
+
+struct val {
+  constexpr operator int() const { return 1; }
+};
+
+// generic lambda (using double template instantiation)
+
+template<typename T>
+void use(T t) {
+  auto lam = [](auto N) {
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brunodf-snps wrote:

I've still added a code comment (see commit e7efc38d) to explain that the guard against a value dependent expression _after_ template instantiation is presently needed, but could in the future become unnecessary (i.e. your remark "ONE day we will fix that").

https://github.com/llvm/llvm-project/pull/172289