Fix some unwanted uses of Debug formatting on user-facing messages

While formatting for user diagnostics used `Display` for all most cases,
some small amount of cases used `Debug` instead.  Until now, `Display`
and `Debug` yielded the same output for many types. However, with path
trimming, we want to show a shorter path for the user, these cases need
fixing.

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

@@ -611,11 +611,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     let sig = self.tcx.fn_sig(did);
                     let bound_output = sig.output();
                     let output = bound_output.skip_binder();
-                    err.span_label(e.span, &format!("this method call resolves to `{:?}`", output));
+                    err.span_label(e.span, &format!("this method call resolves to `{}`", output));
                     let kind = &output.kind;
                     if let ty::Projection(proj) = kind {
                         if let Some(span) = self.tcx.hir().span_if_local(proj.item_def_id) {
-                            err.span_label(span, &format!("`{:?}` defined here", output));
+                            err.span_label(span, &format!("`{}` defined here", output));
                         }
                     }
                 }

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs

@@ -58,8 +58,8 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             .tcx()
             .sess
             .struct_span_err(sp, "`impl` item signature doesn't match `trait` item signature");
-        err.span_label(sp, &format!("found `{:?}`", found));
-        err.span_label(trait_sp, &format!("expected `{:?}`", expected));
+        err.span_label(sp, &format!("found `{}`", found));
+        err.span_label(trait_sp, &format!("expected `{}`", expected));
 
         // Get the span of all the used type parameters in the method.
         let assoc_item = self.tcx().associated_item(trait_def_id);
@@ -92,7 +92,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             err.note_expected_found(&"", expected, &"", found);
         } else {
             // This fallback shouldn't be necessary, but let's keep it in just in case.
-            err.note(&format!("expected `{:?}`\n   found `{:?}`", expected, found));
+            err.note(&format!("expected `{}`\n   found `{}`", expected, found));
         }
         err.span_help(
             type_param_span,

compiler/rustc_middle/src/ty/instance.rs

@@ -260,10 +260,11 @@ impl<'tcx> fmt::Display for Instance<'tcx> {
             InstanceDef::ReifyShim(_) => write!(f, " - shim(reify)"),
             InstanceDef::Intrinsic(_) => write!(f, " - intrinsic"),
             InstanceDef::Virtual(_, num) => write!(f, " - virtual#{}", num),
-            InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({:?})", ty),
+            InstanceDef::FnPtrShim(_, ty) => write!(f, " - shim({})", ty),
             InstanceDef::ClosureOnceShim { .. } => write!(f, " - shim"),
-            InstanceDef::DropGlue(_, ty) => write!(f, " - shim({:?})", ty),
-            InstanceDef::CloneShim(_, ty) => write!(f, " - shim({:?})", ty),
+            InstanceDef::DropGlue(_, None) => write!(f, " - shim(None)"),
+            InstanceDef::DropGlue(_, Some(ty)) => write!(f, " - shim(Some({}))", ty),
+            InstanceDef::CloneShim(_, ty) => write!(f, " - shim({})", ty),
         }
     }
 }

compiler/rustc_middle/src/ty/layout.rs

@@ -174,9 +174,9 @@ pub enum LayoutError<'tcx> {
 impl<'tcx> fmt::Display for LayoutError<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
-            LayoutError::Unknown(ty) => write!(f, "the type `{:?}` has an unknown layout", ty),
+            LayoutError::Unknown(ty) => write!(f, "the type `{}` has an unknown layout", ty),
             LayoutError::SizeOverflow(ty) => {
-                write!(f, "the type `{:?}` is too big for the current architecture", ty)
+                write!(f, "the type `{}` is too big for the current architecture", ty)
             }
         }
     }

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

@@ -1342,8 +1342,8 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
                     .normalize(candidate)
                     .ok();
                 match normalized {
-                    Some(normalized) => format!("\n  {:?}", normalized.value),
-                    None => format!("\n  {:?}", candidate),
+                    Some(normalized) => format!("\n  {}", normalized.value),
+                    None => format!("\n  {}", candidate),
                 }
             })
         };

compiler/rustc_typeck/src/check/mod.rs

@@ -2487,14 +2487,14 @@ fn fn_sig_suggestion<'tcx>(
                             _ => format!("self: {}", ty),
                         }
                     } else {
-                        format!("_: {:?}", ty)
+                        format!("_: {}", ty)
                     }
                 }
                 _ => {
                     if assoc.fn_has_self_parameter && i == 0 {
-                        format!("self: {:?}", ty)
+                        format!("self: {}", ty)
                     } else {
-                        format!("_: {:?}", ty)
+                        format!("_: {}", ty)
                     }
                 }
             })
@@ -2504,7 +2504,7 @@ fn fn_sig_suggestion<'tcx>(
         .collect::<Vec<String>>()
         .join(", ");
     let output = sig.output();
-    let output = if !output.is_unit() { format!(" -> {:?}", output) } else { String::new() };
+    let output = if !output.is_unit() { format!(" -> {}", output) } else { String::new() };
 
     let unsafety = sig.unsafety.prefix_str();
     let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates);
@@ -2542,7 +2542,7 @@ fn suggestion_signature(assoc: &ty::AssocItem, tcx: TyCtxt<'_>) -> String {
         ty::AssocKind::Const => {
             let ty = tcx.type_of(assoc.def_id);
             let val = expr::ty_kind_suggestion(ty).unwrap_or("value");
-            format!("const {}: {:?} = {};", assoc.ident, ty, val)
+            format!("const {}: {} = {};", assoc.ident, ty, val)
         }
     }
 }

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -1177,7 +1177,7 @@ fn e0307(fcx: &FnCtxt<'fcx, 'tcx>, span: Span, receiver_ty: Ty<'_>) {
         fcx.tcx.sess.diagnostic(),
         span,
         E0307,
-        "invalid `self` parameter type: {:?}",
+        "invalid `self` parameter type: {}",
         receiver_ty,
     )
     .note("type of `self` must be `Self` or a type that dereferences to it")