Bug 13967 – More precise non-@nogc error messages

From the first error message it seems "joiner" is @nogc, but the second error message shows that it's the iteration of r1 (calling its .front) non-@nogc: void main() { import std.range: iota; import std.algorithm: map, joiner; static foo(in uint n) @nogc { auto r1 = n.iota.map!(x => x.iota.map!(y => x)); auto r2 = r1.joiner; foreach (z; r1) {} } } test.d(6,21): Error: @nogc function 'test.main.foo' cannot call non-@nogc function 'std.algorithm.joiner!(MapResult!(__lambda2, Result)).joiner' test.d(7,9): Error: @nogc function 'test.main.foo' cannot call non-@nogc function 'test.main.foo.MapResult!(__lambda2, Result).MapResult.front' I'd like error messages to better pinpoint where the non-@nogc actually is. Because with library functions like "joiner" you know they are designed to be @nogc, but with user-written ranges it's harder to find where the problem is. See also Issue 12829

This code has been changed to being fully inferred to @nogc from 2.068, so today no @nogc violation errors happen with the example case. And, the diagnostic improvement is done in master, by fixing issue 12829. Mark as resolved-worksforme.