Bug 23424 – improve error when template instantiation doesn't match any overload

If I create a template that accepts a type, and try to instantiate it with something other than a type, it fails with a clear message: ```d template T(X) { int v; } void main() { T!(1).v = 5; } ``` Error: template instance `T!1` does not match template declaration `T(X)` However, if I create just one overload, it no longer helps me with the clear message: ```d template T(X) { int v; } template T() { int v; } void main() { T!(1).v = 5; } ``` Error: template `onlineapp.T` does not match any template declaration It tells me the template FQN, but the "does not match any template declaration" is puzzling -- yes, it doesn't match any overloaded declaration, but it seems to suggest there is no declaration. Comparing to a failure to match a function template: ```d void T(X)() { int v; } void T()() { int v; } void main() { T!(1)(); } ``` Error: none of the overloads of template `onlineapp.T` are callable using argument types `!(1)()` Candidates are: `T(X)()` `T()()` This is very clear and informative. It also identifies possible things that it tries, just like the non-overloaded template example. A similar approach should be done for non-function templates.

@ntrel created dlang/dmd pull request #14603 "Issue 23424 - improve error when template instantiation doesn't match…" mentioning this issue: - Issue 23424 - improve error when template instantiation doesn't match any overload https://github.com/dlang/dmd/pull/14603

dlang/dmd pull request #14603 "Fix Issue 23424 - improve error when template instantiation doesn't match an overload" was merged into master: - c0243596948a75e709c96afbbf9d48919f884bb4 by Nick Treleaven: Fix Issue 23424 - improve error when template instantiation doesn't match any overload https://github.com/dlang/dmd/pull/14603