[clang] [clang][Sema] Improve template argument deduction diagnostic (PR #122754)

[Matheus Izvekov via cfe-commits]

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@@ -4870,14 +4870,17 @@ def note_ovl_candidate_inconsistent_deduction_types : Note<
     "candidate template ignored: deduced values %diff{"
     "of conflicting types for parameter %0 (%1 of type $ vs. %3 of type $)|"
     "%1 and %3 of conflicting types for parameter %0}2,4">;
-def note_ovl_candidate_explicit_arg_mismatch_named : Note<
-    "candidate template ignored: invalid explicitly-specified argument "
-    "for template parameter %0">;
+
+def note_ovl_candidate_explicit_arg_mismatch : Note<
+    "candidate template ignored: invalid explicitly-specified argument"
+    "%select{"
+    "|: %select{non-type|type}1 argument %select{'%3'|%3}1 is not compatible with "
+    "%select{non-type|type}2 parameter %select{%5|%4}2"
+    "|: could not convert '%3' from %4 to %5"
+    "| for %ordinal6 template parameter}0">;
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mizvekov wrote:

You don't need to talk about the parameter since we emit a separate note for it, that should make this diagnostic a bit simpler, as right now it's stretching it on complexity.

If we are talking about argument / parameter kinds, it would make sense to talk about 'template' kind, besides non-type and type, otherwise some mismatches could happen between non-type kinds and that's a bit confusing.

https://github.com/llvm/llvm-project/pull/122754