Auto merge of #54591 - ljedrz:cleanup_typeck_rest, r=zackmdavis

A few cleanups and minor improvements to typeck

This PR complements #54533, which was limited to `check`.

- change a few `push` loops to `extend`s
- prefer `to_owned` to `to_string` for string literals
- prefer `if let` to `match` where only one branch matters
- a few other minor improvements
- whitespace fixes

Author: bors

src/librustc_typeck/astconv.rs

@@ -147,7 +147,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                     bound_region: ty::BrNamed(id, name)
                 }))
 
-                    // (*) -- not late-bound, won't change
+                // (*) -- not late-bound, won't change
             }
 
             None => {
@@ -167,8 +167,8 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         };
 
         debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
-                lifetime,
-                r);
+               lifetime,
+               r);
 
         r
     }
@@ -218,7 +218,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                 span,
                 E0632,
                 "cannot provide explicit type parameters when `impl Trait` is \
-                used in argument position."
+                 used in argument position."
             };
 
             err.emit();
@@ -538,7 +538,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         // region with the current anon region binding (in other words,
         // whatever & would get replaced with).
         debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
-               generic_args={:?})",
+                generic_args={:?})",
                def_id, self_ty, generic_args);
 
         let tcx = self.tcx();
@@ -609,7 +609,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                             if default_needs_object_self(param) {
                                 struct_span_err!(tcx.sess, span, E0393,
                                                     "the type parameter `{}` must be explicitly \
-                                                    specified",
+                                                     specified",
                                                     param.name)
                                     .span_label(span,
                                                 format!("missing reference to `{}`", param.name))
@@ -623,7 +623,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                                 self.normalize_ty(
                                     span,
                                     tcx.at(span).type_of(param.def_id)
-                                        .subst_spanned(tcx, substs.unwrap(), Some(span))
+                                       .subst_spanned(tcx, substs.unwrap(), Some(span))
                                 ).into()
                             }
                         } else if infer_types {
@@ -851,7 +851,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                                 binding.span,
                                 E0582,
                                 "binding for associated type `{}` references lifetime `{}`, \
-                                which does not appear in the trait input types",
+                                 which does not appear in the trait input types",
                                 binding.item_name, br_name)
                     .emit();
             }
@@ -891,7 +891,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                         ref_id,
                         binding.span,
                         &format!("associated type binding `{}` specified more than once",
-                                binding.item_name)
+                                 binding.item_name)
                     );
                     err.span_label(binding.span, "used more than once");
                     err.span_label(*prev_span, format!("first use of `{}`", binding.item_name));
@@ -994,7 +994,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         if !object_safety_violations.is_empty() {
             tcx.report_object_safety_error(
                 span, principal.def_id(), object_safety_violations)
-                .emit();
+               .emit();
             return tcx.types.err;
         }
 
@@ -1014,13 +1014,13 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         for item_def_id in associated_types {
             let assoc_item = tcx.associated_item(item_def_id);
             let trait_def_id = assoc_item.container.id();
-            struct_span_err!(tcx.sess, span, E0191,
-                "the value of the associated type `{}` (from the trait `{}`) must be specified",
-                        assoc_item.ident,
-                        tcx.item_path_str(trait_def_id))
-                        .span_label(span, format!(
-                            "missing associated type `{}` value", assoc_item.ident))
-                        .emit();
+            struct_span_err!(tcx.sess, span, E0191, "the value of the associated type `{}` \
+                                                     (from the trait `{}`) must be specified",
+                                                    assoc_item.ident,
+                                                    tcx.item_path_str(trait_def_id))
+                .span_label(span, format!("missing associated type `{}` value",
+                                          assoc_item.ident))
+                .emit();
         }
 
         // Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
@@ -1032,12 +1032,11 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
             iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
             .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
             .chain(existential_projections
-                   .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
+                .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
             .collect::<SmallVec<[_; 8]>>();
         v.sort_by(|a, b| a.stable_cmp(tcx, b));
         let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
 
-
         // Explicitly specified region bound. Use that.
         let region_bound = if !lifetime.is_elided() {
             self.ast_region_to_region(lifetime, None)
@@ -1072,7 +1071,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
             .span_label(span, "ambiguous associated type")
             .note(&format!("specify the type using the syntax `<{} as {}>::{}`",
-                  type_str, trait_str, name))
+                           type_str, trait_str, name))
             .emit();
 
     }
@@ -1094,8 +1093,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
 
         // Check that there is exactly one way to find an associated type with the
         // correct name.
-        let suitable_bounds =
-            traits::transitive_bounds(tcx, &bounds)
+        let suitable_bounds = traits::transitive_bounds(tcx, &bounds)
             .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
 
         let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
@@ -1110,20 +1108,20 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
     // Checks that bounds contains exactly one element and reports appropriate
     // errors otherwise.
     fn one_bound_for_assoc_type<I>(&self,
-                                mut bounds: I,
-                                ty_param_name: &str,
-                                assoc_name: ast::Ident,
-                                span: Span)
+                                   mut bounds: I,
+                                   ty_param_name: &str,
+                                   assoc_name: ast::Ident,
+                                   span: Span)
         -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
         where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
     {
         let bound = match bounds.next() {
             Some(bound) => bound,
             None => {
                 struct_span_err!(self.tcx().sess, span, E0220,
-                          "associated type `{}` not found for `{}`",
-                          assoc_name,
-                          ty_param_name)
+                                 "associated type `{}` not found for `{}`",
+                                 assoc_name,
+                                 ty_param_name)
                   .span_label(span, format!("associated type `{}` not found", assoc_name))
                   .emit();
                 return Err(ErrorReported);
@@ -1142,14 +1140,14 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
             for bound in bounds {
                 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
                     item.kind == ty::AssociatedKind::Type &&
-                    self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
+                        self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
                 })
                 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
 
                 if let Some(span) = bound_span {
                     err.span_label(span, format!("ambiguous `{}` from `{}`",
-                                                  assoc_name,
-                                                  bound));
+                                                 assoc_name,
+                                                 bound));
                 } else {
                     span_note!(&mut err, span,
                                "associated type `{}` could derive from `{}`",
@@ -1198,8 +1196,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                     }
                 };
 
-                let candidates =
-                    traits::supertraits(tcx, ty::Binder::bind(trait_ref))
+                let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
                     .filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
 
                 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
@@ -1230,7 +1227,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name, trait_did, ref_id);
         let item = tcx.associated_items(trait_did).find(|i| {
             Namespace::from(i.kind) == Namespace::Type &&
-            i.ident.modern() == assoc_ident
+                i.ident.modern() == assoc_ident
         })
         .expect("missing associated type");
 
@@ -1293,16 +1290,15 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
                             if err_for_lt { continue }
                             err_for_lt = true;
                             (struct_span_err!(self.tcx().sess, lt.span, E0110,
-                                            "lifetime parameters are not allowed on \
-                                                this type"),
+                                              "lifetime parameters are not allowed on this type"),
                              lt.span,
                              "lifetime")
                         }
                         hir::GenericArg::Type(ty) => {
                             if err_for_ty { continue }
                             err_for_ty = true;
                             (struct_span_err!(self.tcx().sess, ty.span, E0109,
-                                            "type parameters are not allowed on this type"),
+                                              "type parameters are not allowed on this type"),
                              ty.span,
                              "type")
                         }
@@ -1590,7 +1586,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
         ));
 
         // Find any late-bound regions declared in return type that do
-        // not appear in the arguments. These are not wellformed.
+        // not appear in the arguments. These are not well-formed.
         //
         // Example:
         //     for<'a> fn() -> &'a str <-- 'a is bad

src/librustc_typeck/check_unused.rs

@@ -75,7 +75,7 @@ impl<'a, 'tcx> CheckVisitor<'a, 'tcx> {
         let msg = if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
             format!("unused import: `{}`", snippet)
         } else {
-            "unused import".to_string()
+            "unused import".to_owned()
         };
         self.tcx.lint_node(lint::builtin::UNUSED_IMPORTS, id, span, &msg);
     }

src/librustc_typeck/coherence/builtin.rs

@@ -55,33 +55,29 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
 }
 
 fn visit_implementation_of_drop<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, impl_did: DefId) {
-    match tcx.type_of(impl_did).sty {
-        ty::Adt(..) => {}
-        _ => {
-            // Destructors only work on nominal types.
-            if let Some(impl_node_id) = tcx.hir.as_local_node_id(impl_did) {
-                match tcx.hir.find(impl_node_id) {
-                    Some(Node::Item(item)) => {
-                        let span = match item.node {
-                            ItemKind::Impl(.., ref ty, _) => ty.span,
-                            _ => item.span,
-                        };
-                        struct_span_err!(tcx.sess,
-                                         span,
-                                         E0120,
-                                         "the Drop trait may only be implemented on \
-                                         structures")
-                            .span_label(span, "implementing Drop requires a struct")
-                            .emit();
-                    }
-                    _ => {
-                        bug!("didn't find impl in ast map");
-                    }
-                }
+    if let ty::Adt(..) = tcx.type_of(impl_did).sty {
+        /* do nothing */
+    } else {
+        // Destructors only work on nominal types.
+        if let Some(impl_node_id) = tcx.hir.as_local_node_id(impl_did) {
+            if let Some(Node::Item(item)) = tcx.hir.find(impl_node_id) {
+                let span = match item.node {
+                    ItemKind::Impl(.., ref ty, _) => ty.span,
+                    _ => item.span,
+                };
+                struct_span_err!(tcx.sess,
+                                 span,
+                                 E0120,
+                                 "the Drop trait may only be implemented on \
+                                  structures")
+                    .span_label(span, "implementing Drop requires a struct")
+                    .emit();
             } else {
-                bug!("found external impl of Drop trait on \
-                      something other than a struct");
+                bug!("didn't find impl in ast map");
             }
+        } else {
+            bug!("found external impl of Drop trait on \
+                  something other than a struct");
         }
     }
 }
@@ -92,8 +88,7 @@ fn visit_implementation_of_copy<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, impl_did:
     let impl_node_id = if let Some(n) = tcx.hir.as_local_node_id(impl_did) {
         n
     } else {
-        debug!("visit_implementation_of_copy(): impl not in this \
-                crate");
+        debug!("visit_implementation_of_copy(): impl not in this crate");
         return;
     };
 
@@ -119,11 +114,11 @@ fn visit_implementation_of_copy<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, impl_did:
             };
 
             let mut err = struct_span_err!(tcx.sess,
-                                          span,
-                                          E0204,
-                                          "the trait `Copy` may not be implemented for this type");
+                                           span,
+                                           E0204,
+                                           "the trait `Copy` may not be implemented for this type");
             for span in fields.iter().map(|f| tcx.def_span(f.did)) {
-                    err.span_label(span, "this field does not implement `Copy`");
+                err.span_label(span, "this field does not implement `Copy`");
             }
             err.emit()
         }
@@ -173,12 +168,9 @@ pub fn coerce_unsized_info<'a, 'gcx>(gcx: TyCtxt<'a, 'gcx, 'gcx>,
     debug!("compute_coerce_unsized_info(impl_did={:?})", impl_did);
     let coerce_unsized_trait = gcx.lang_items().coerce_unsized_trait().unwrap();
 
-    let unsize_trait = match gcx.lang_items().require(UnsizeTraitLangItem) {
-        Ok(id) => id,
-        Err(err) => {
-            gcx.sess.fatal(&format!("`CoerceUnsized` implementation {}", err));
-        }
-    };
+    let unsize_trait = gcx.lang_items().require(UnsizeTraitLangItem).unwrap_or_else(|err| {
+        gcx.sess.fatal(&format!("`CoerceUnsized` implementation {}", err));
+    });
 
     // this provider should only get invoked for local def-ids
     let impl_node_id = gcx.hir.as_local_node_id(impl_did).unwrap_or_else(|| {
@@ -210,9 +202,9 @@ pub fn coerce_unsized_info<'a, 'gcx>(gcx: TyCtxt<'a, 'gcx, 'gcx>,
                            mk_ptr: &dyn Fn(Ty<'gcx>) -> Ty<'gcx>| {
             if (mt_a.mutbl, mt_b.mutbl) == (hir::MutImmutable, hir::MutMutable) {
                 infcx.report_mismatched_types(&cause,
-                                             mk_ptr(mt_b.ty),
-                                             target,
-                                             ty::error::TypeError::Mutability)
+                                              mk_ptr(mt_b.ty),
+                                              target,
+                                              ty::error::TypeError::Mutability)
                     .emit();
             }
             (mt_a.ty, mt_b.ty, unsize_trait, None)
@@ -235,7 +227,7 @@ pub fn coerce_unsized_info<'a, 'gcx>(gcx: TyCtxt<'a, 'gcx, 'gcx>,
             }
 
             (&ty::Adt(def_a, substs_a), &ty::Adt(def_b, substs_b)) if def_a.is_struct() &&
-                                                                          def_b.is_struct() => {
+                                                                      def_b.is_struct() => {
                 if def_a != def_b {
                     let source_path = gcx.item_path_str(def_a.did);
                     let target_path = gcx.item_path_str(def_b.did);

src/librustc_typeck/coherence/inherent_impls.rs

@@ -315,8 +315,7 @@ impl<'a, 'tcx> InherentCollect<'a, 'tcx> {
                              E0116,
                              "cannot define inherent `impl` for a type outside of the crate \
                               where the type is defined")
-                .span_label(item.span,
-                            "impl for type defined outside of crate.")
+                .span_label(item.span, "impl for type defined outside of crate.")
                 .note("define and implement a trait or new type instead")
                 .emit();
         }

src/librustc_typeck/coherence/mod.rs

@@ -36,8 +36,8 @@ fn check_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, node_id: ast::NodeId) {
 
     if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
         debug!("(checking implementation) adding impl for trait '{:?}', item '{}'",
-                trait_ref,
-                tcx.item_path_str(impl_def_id));
+               trait_ref,
+               tcx.item_path_str(impl_def_id));
 
         // Skip impls where one of the self type is an error type.
         // This occurs with e.g. resolve failures (#30589).