[clang] [clang] Add tests for DRs about complete-class context (PR #77444)

[Vlad Serebrennikov via cfe-commits]

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@@ -42,6 +42,28 @@ namespace dr1611 { // dr1611: dup 1658
   C c;
 }
 
+namespace dr1626 { // dr1626: no open
+// FIXME: current consensus for CWG2335 is that the examples are well-formed.
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Endilll wrote:

Intent expressed in P1787 in PR description seems rather clear to me, as well as its application to CWG1626, but I don't insist.

https://github.com/llvm/llvm-project/pull/77444