Rollup merge of #106131 - compiler-errors:not-ptrs, r=davidtwco

Mention "signature" rather than "fn pointer" when impl/trait methods are incompatible

Fixes #80929
Fixes #67296

compiler/rustc_infer/src/infer/mod.rs

@@ -361,6 +361,7 @@ pub enum ValuePairs<'tcx> {
     Terms(ExpectedFound<ty::Term<'tcx>>),
     TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
     PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
+    Sigs(ExpectedFound<ty::FnSig<'tcx>>),
 }
 
 impl<'tcx> ValuePairs<'tcx> {