[PATCH] D113874: [clang] Propagate requires-clause from constructor template to implicit deduction guide

[Sam McCall via Phabricator via cfe-commits]

sammccall accepted this revision.
sammccall added a comment.
This revision is now accepted and ready to land.

Fantastic, thank you!



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Comment at: clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp:794
 
+TEST(DiagnosticsTest, ConstrainedImplicitDeductionGuides) {
+  Annotations Header(R"cpp(
----------------
Having solved and tested this in the AST, this test is arguably redundant (it's not like there's anything interesting going on in de/serialization).

Happy if you want to keep it as a regression test, maybe leave a comment that we used to crash here or linking to the bug?


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Comment at: clang/test/SemaTemplate/deduction-guide.cpp:219
+
+template <typename T> F(T) -> F<>;
+
----------------
Before your patch, clang requires this explicit deduction guide in order to accept the code.
Without it, it says the two implicit deduction guides from the constructor are ambiguous. But this is precisely because they lack the constraints!

After your patch, clang accepts this code without the explicit deduction guide.
So I think omitting the guide (and having no `expected-error...`) makes it a better test - in addition to verifying the guides can be dumped, it checks they are used.

(Kadir and I spent some time poking at variations of this example to understand how CTAD works in the AST, so thanks for this!)


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  https://reviews.llvm.org/D113874/new/

https://reviews.llvm.org/D113874