Allow using only types in `TEMPLATE_TEST_CASE_SIG`. (#2995)

Right now `TEMPLATE_TEST_CASE_SIG` fails to compile when the signature contains only types:

```
TEMPLATE_TEST_CASE_SIG(
  "TemplateTestSig: compiles with two type parameters",
  "[template][onlytypes]",
  ((typename U, typename V), U, V), (int,int)) {}
```

The trick is to resolve the ambiguity between the two overloads of
`get_wrapper` (`TypeList` and `Nttp`) by making one match more strongly.
We also need to allow `reg_test` to register more than one type.

Add unit tests.

Fixes #2680

---------

Co-authored-by: Martin Hořeňovský <martin.horenovsky@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/SelfTest/UsageTests/Misc.tests.cpp b/tests/SelfTest/UsageTests/Misc.tests.cpp
index 3697f069..464a4b1d 100644
--- a/tests/SelfTest/UsageTests/Misc.tests.cpp
+++ b/tests/SelfTest/UsageTests/Misc.tests.cpp
@@ -334,6 +334,10 @@ TEMPLATE_TEST_CASE( "TemplateTest: vectors can be sized and resized", "[vector][
     }
 }
 
+TEMPLATE_TEST_CASE_SIG("TemplateTestSig: compiles with a single int parameter", "[template][singleint]", ((int V), V), 1, 3, 6) {}
+
+TEMPLATE_TEST_CASE_SIG("TemplateTestSig: compiles with two type parameters", "[template][onlytypes]", ((typename U, typename V), U, V), (int,int)) {}
+
 TEMPLATE_TEST_CASE_SIG("TemplateTestSig: vectors can be sized and resized", "[vector][template][nttp]", ((typename TestType, int V), TestType, V), (int,5), (float,4), (std::string,15), ((std::tuple<int, float>), 6)) {
 
     std::vector<TestType> v(V);