Bug 5738 – error message for template mismatch could be better

void bla(T...)(T args) { foreach(idx, arg; args) blub(idx, arg); } void blub(T)(short idx, T arg) // on x64, replace short with int to get a more real world case { } void main() { bla(5, 2); } templ.d(4): Error: template templ.blub(T) does not match any function template declaration templ.d(4): Error: template templ.blub(T) cannot deduce template function from argument types !()(uint,int) templ.d(4): Error: template templ.blub(T) does not match any function template declaration templ.d(4): Error: template templ.blub(T) cannot deduce template function from argument types !()(uint,int) templ.d(13): Error: template instance templ.bla!(int,int) error instantiating It wasn't obvious for me that it couldn't implicitly convert the idx argument.

another more cryptic example is the following: void bla() {} class Blub { U getInfo(U, alias infoFunction = bla)(uint infoname) { return 0; } uint referenceCount() const { return getInfo!uint(55u); } } refconst.d(12): Error: template refconst.Blub.getInfo(U,alias infoFunction = bla) does not match any function template declaration refconst.d(12): Error: template refconst.Blub.getInfo(U,alias infoFunction = bla) cannot deduce template function from argument types !(uint)(uint) The problem is that getInfo needs to be const as well, but there's no hint whatsoever. It's hard to detect that in a big codebase. Removing alias infoFunction from getInfo results in a slightly less cryptic (but still non-intuitiv message, but that's another issue: http://d.puremagic.com/issues/show_bug.cgi?id=4497): refconst.d(10): Error: function refconst.Blub.getInfo!(uint).getInfo (uint infoname) is not callable using argument types (uint) const

(In reply to comment #0) [snip] This code works with 2.063a(git head). IFTI bug might be already fixed. (In reply to comment #1) Compiler now reports following errors for the invalid code. test.d(12): Error: mutable method test.Blub.getInfo!(uint).getInfo is not callable using a const object