Rollup merge of #106754 - compiler-errors:ty-infer-method-is-confusing, r=lcnr

Rename `Ty::is_ty_infer` -> `Ty::is_ty_or_numeric_infer`

Makes sure people are aware that they may have a type variable *or* an int/float variable.

r? `@oli-obk` https://github.com/rust-lang/rust/pull/106322#issuecomment-1376913539 but I could instead implement your solution, let me know.

(This will conflict with #106322 for now, ignore that 😄)

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1782,9 +1782,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             // like when you have two references but one is `usize` and the other
                             // is `f32`. In those cases we still want to show the `note`. If the
                             // value from `ef` is `Infer(_)`, then we ignore it.
-                            if !ef.expected.is_ty_infer() {
+                            if !ef.expected.is_ty_or_numeric_infer() {
                                 ef.expected != values.expected
-                            } else if !ef.found.is_ty_infer() {
+                            } else if !ef.found.is_ty_or_numeric_infer() {
                                 ef.found != values.found
                             } else {
                                 false

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -78,7 +78,7 @@ impl InferenceDiagnosticsData {
     }
 
     fn where_x_is_kind(&self, in_type: Ty<'_>) -> &'static str {
-        if in_type.is_ty_infer() {
+        if in_type.is_ty_or_numeric_infer() {
             ""
         } else if self.name == "_" {
             // FIXME: Consider specializing this message if there is a single `_`
@@ -195,12 +195,12 @@ fn ty_to_string<'tcx>(
         // invalid pseudo-syntax, we want the `fn`-pointer output instead.
         (ty::FnDef(..), _) => ty.fn_sig(infcx.tcx).print(printer).unwrap().into_buffer(),
         (_, Some(def_id))
-            if ty.is_ty_infer()
+            if ty.is_ty_or_numeric_infer()
                 && infcx.tcx.get_diagnostic_item(sym::iterator_collect_fn) == Some(def_id) =>
         {
             "Vec<_>".to_string()
         }
-        _ if ty.is_ty_infer() => "/* Type */".to_string(),
+        _ if ty.is_ty_or_numeric_infer() => "/* Type */".to_string(),
         // FIXME: The same thing for closures, but this only works when the closure
         // does not capture anything.
         //
@@ -680,7 +680,7 @@ impl<'tcx> InferSourceKind<'tcx> {
             | InferSourceKind::ClosureReturn { ty, .. } => {
                 if ty.is_closure() {
                     ("closure", closure_as_fn_str(infcx, ty))
-                } else if !ty.is_ty_infer() {
+                } else if !ty.is_ty_or_numeric_infer() {
                     ("normal", ty_to_string(infcx, ty, None))
                 } else {
                     ("other", String::new())
@@ -813,7 +813,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
         self.attempt += 1;
         if let Some(InferSource { kind: InferSourceKind::GenericArg { def_id: did, ..}, .. }) = self.infer_source
             && let InferSourceKind::LetBinding { ref ty, ref mut def_id, ..} = new_source.kind
-            && ty.is_ty_infer()
+            && ty.is_ty_or_numeric_infer()
         {
             // Customize the output so we talk about `let x: Vec<_> = iter.collect();` instead of
             // `let x: _ = iter.collect();`, as this is a very common case.

compiler/rustc_middle/src/ty/sty.rs

@@ -1686,7 +1686,7 @@ impl<'tcx> Ty<'tcx> {
     }
 
     #[inline]
-    pub fn is_ty_infer(self) -> bool {
+    pub fn is_ty_or_numeric_infer(self) -> bool {
         matches!(self.kind(), Infer(_))
     }
 

compiler/rustc_middle/src/ty/subst.rs

@@ -202,7 +202,7 @@ impl<'tcx> GenericArg<'tcx> {
     pub fn is_non_region_infer(self) -> bool {
         match self.unpack() {
             GenericArgKind::Lifetime(_) => false,
-            GenericArgKind::Type(ty) => ty.is_ty_infer(),
+            GenericArgKind::Type(ty) => ty.is_ty_or_numeric_infer(),
             GenericArgKind::Const(ct) => ct.is_ct_infer(),
         }
     }

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -2252,8 +2252,11 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     Ok(None) => {
                         let ambiguities =
                             ambiguity::recompute_applicable_impls(self.infcx, &obligation);
-                        let has_non_region_infer =
+                        let has_non_region_infer = trait_ref
-                            trait_ref.skip_binder().substs.types().any(|t| !t.is_ty_infer());
+                            .skip_binder()
+                            .substs
+                            .types()
+                            .any(|t| !t.is_ty_or_numeric_infer());
                         // It doesn't make sense to talk about applicable impls if there are more
                         // than a handful of them.
                         if ambiguities.len() > 1 && ambiguities.len() < 10 && has_non_region_infer {