[clang] [clang] Add tests for some of CWG issues resolved in Croydon (2026-03) (PR #189299)

[Corentin Jabot via cfe-commits]

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@@ -174,6 +193,40 @@ static_assert(!__is_layout_compatible(StructWithAnonUnion, StructWithAnonUnion3)
 #endif
 } // namespace cwg2759
 
+namespace cwg2765 { // cwg2765: partial
+static_assert(+"foo" == "foo", "");
+// expected-error at -1 {{static assertion expression is not an integral constant expression}}
+//   expected-note at -2 {{comparison of addresses of potentially overlapping literals has unspecified value}}
+static_assert("xfoo" + 1 == "foo\0y", "");
+// expected-warning at -1 {{adding 'int' to a string does not append to the string}}
+//   expected-note at -2 {{use array indexing to silence this warning}}
+// expected-error at -3 {{static assertion expression is not an integral constant expression}}
+//   expected-note at -4 {{comparison of addresses of potentially overlapping literals has unspecified value}}
+static_assert("foo" + 0 != "bar", "");
+// expected-warning at -1 {{adding 'int' to a string does not append to the string}}
+//   expected-note at -2 {{use array indexing to silence this warning}}
+// cxx98-error at -3 {{static assertion expression is not an integral constant expression}} FIXME
+static_assert((const char*)"foo" != "oo", "");
+// cxx98-error at -1 {{static assertion expression is not an integral constant expression}} FIXME
+
+#if __cplusplus >= 201103L
+constexpr const char *f() { return "foo"; }
+constexpr bool b2 = f() == f(); 
+// since-cxx11-error at -1 {{constexpr variable 'b2' must be initialized by a constant expression}}
+//   since-cxx11-note at -2 {{comparison of addresses of potentially overlapping literals has unspecified value}}
+constexpr const char *p = f();
+constexpr bool b3 = p == p; 
+#endif
+
+#if __cplusplus >= 201402L
+constexpr std::initializer_list<int *> il1 = { (int *)nullptr };
+constexpr std::initializer_list<unsigned long> il2 = { 0 };
+constexpr bool b7 = il1.begin() == (void *)il2.begin();
+// FIXME-error at -1 {{constexpr variable 'b2' must be initialized by a constant expression}}
+//   FIXME-note at -2 {{address of a constexpr-unknown object cannot be used for comparison}}
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cor3ntin wrote:

So, why do you expect this to fail?

https://github.com/llvm/llvm-project/pull/189299