Rollup merge of rust-lang#57477 - euclio:clarify-lev-suggestion, r=za…

…ckmdavis

clarify resolve typo suggestion

Include the kind of the binding that we're suggesting, and use a
structured suggestion.

Fixes rust-lang#53445.

src/librustc/hir/def.rs

@@ -284,7 +284,7 @@ impl Def {
         }
     }
 
-    /// A human readable kind name
+    /// A human readable name for the def kind ("function", "module", etc.).
     pub fn kind_name(&self) -> &'static str {
         match *self {
             Def::Fn(..) => "function",
@@ -324,6 +324,7 @@ impl Def {
         }
     }
 
+    /// An English article for the def.
     pub fn article(&self) -> &'static str {
         match *self {
             Def::AssociatedTy(..) | Def::AssociatedConst(..) | Def::AssociatedExistential(..) |

src/librustc_resolve/lib.rs

@@ -120,6 +120,16 @@ struct BindingError {
     target: BTreeSet<Span>,
 }
 
+struct TypoSuggestion {
+    candidate: Symbol,
+
+    /// The kind of the binding ("crate", "module", etc.)
+    kind: &'static str,
+
+    /// An appropriate article to refer to the binding ("a", "an", etc.)
+    article: &'static str,
+}
+
 impl PartialOrd for BindingError {
     fn partial_cmp(&self, other: &BindingError) -> Option<cmp::Ordering> {
         Some(self.cmp(other))
@@ -1448,7 +1458,7 @@ impl PrimitiveTypeTable {
     }
 }
 
-#[derive(Default, Clone)]
+#[derive(Debug, Default, Clone)]
 pub struct ExternPreludeEntry<'a> {
     extern_crate_item: Option<&'a NameBinding<'a>>,
     pub introduced_by_item: bool,
@@ -3291,8 +3301,19 @@ impl<'a> Resolver<'a> {
             let mut levenshtein_worked = false;
 
             // Try Levenshtein algorithm.
-            if let Some(candidate) = this.lookup_typo_candidate(path, ns, is_expected, span) {
-                err.span_label(ident_span, format!("did you mean `{}`?", candidate));
+            let suggestion = this.lookup_typo_candidate(path, ns, is_expected, span);
+            if let Some(suggestion) = suggestion {
+                let msg = format!(
+                    "{} {} with a similar name exists",
+                    suggestion.article, suggestion.kind
+                );
+                err.span_suggestion_with_applicability(
+                    ident_span,
+                    &msg,
+                    suggestion.candidate.to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+
                 levenshtein_worked = true;
             }
 
@@ -4183,19 +4204,25 @@ impl<'a> Resolver<'a> {
         None
     }
 
-    fn lookup_typo_candidate<FilterFn>(&mut self,
-                                       path: &[Segment],
-                                       ns: Namespace,
-                                       filter_fn: FilterFn,
-                                       span: Span)
-                                       -> Option<Symbol>
-        where FilterFn: Fn(Def) -> bool
+    fn lookup_typo_candidate<FilterFn>(
+        &mut self,
+        path: &[Segment],
+        ns: Namespace,
+        filter_fn: FilterFn,
+        span: Span,
+    ) -> Option<TypoSuggestion>
+    where
+        FilterFn: Fn(Def) -> bool,
     {
-        let add_module_candidates = |module: Module, names: &mut Vec<Name>| {
+        let add_module_candidates = |module: Module, names: &mut Vec<TypoSuggestion>| {
             for (&(ident, _), resolution) in module.resolutions.borrow().iter() {
                 if let Some(binding) = resolution.borrow().binding {
                     if filter_fn(binding.def()) {
-                        names.push(ident.name);
+                        names.push(TypoSuggestion {
+                            candidate: ident.name,
+                            article: binding.def().article(),
+                            kind: binding.def().kind_name(),
+                        });
                     }
                 }
             }
@@ -4209,7 +4236,11 @@ impl<'a> Resolver<'a> {
                 // Locals and type parameters
                 for (ident, def) in &rib.bindings {
                     if filter_fn(*def) {
-                        names.push(ident.name);
+                        names.push(TypoSuggestion {
+                            candidate: ident.name,
+                            article: def.article(),
+                            kind: def.kind_name(),
+                        });
                     }
                 }
                 // Items in scope
@@ -4222,7 +4253,13 @@ impl<'a> Resolver<'a> {
                     } else {
                         // Items from the prelude
                         if !module.no_implicit_prelude {
-                            names.extend(self.extern_prelude.iter().map(|(ident, _)| ident.name));
+                            names.extend(self.extern_prelude.iter().map(|(ident, _)| {
+                                TypoSuggestion {
+                                    candidate: ident.name,
+                                    article: "a",
+                                    kind: "crate",
+                                }
+                            }));
                             if let Some(prelude) = self.prelude {
                                 add_module_candidates(prelude, &mut names);
                             }
@@ -4234,7 +4271,13 @@ impl<'a> Resolver<'a> {
             // Add primitive types to the mix
             if filter_fn(Def::PrimTy(Bool)) {
                 names.extend(
-                    self.primitive_type_table.primitive_types.iter().map(|(name, _)| name)
+                    self.primitive_type_table.primitive_types.iter().map(|(name, _)| {
+                        TypoSuggestion {
+                            candidate: *name,
+                            article: "a",
+                            kind: "primitive type",
+                        }
+                    })
                 )
             }
         } else {
@@ -4251,9 +4294,16 @@ impl<'a> Resolver<'a> {
 
         let name = path[path.len() - 1].ident.name;
         // Make sure error reporting is deterministic.
-        names.sort_by_cached_key(|name| name.as_str());
-        match find_best_match_for_name(names.iter(), &name.as_str(), None) {
-            Some(found) if found != name => Some(found),
+        names.sort_by_cached_key(|suggestion| suggestion.candidate.as_str());
+
+        match find_best_match_for_name(
+            names.iter().map(|suggestion| &suggestion.candidate),
+            &name.as_str(),
+            None,
+        ) {
+            Some(found) if found != name => names
+                .into_iter()
+                .find(|suggestion| suggestion.candidate == found),
             _ => None,
         }
     }

src/librustc_resolve/macros.rs

@@ -1015,6 +1015,7 @@ impl<'a> Resolver<'a> {
             };
             let ident = Ident::new(Symbol::intern(name), span);
             self.lookup_typo_candidate(&[Segment::from_ident(ident)], MacroNS, is_macro, span)
+                .map(|suggestion| suggestion.candidate)
         });
 
         if let Some(suggestion) = suggestion {

src/test/ui/associated-types/associated-types-eq-1.stderr

@@ -2,7 +2,7 @@ error[E0412]: cannot find type `A` in this scope
   --> $DIR/associated-types-eq-1.rs:10:12
    |
 LL |     let _: A = x.boo(); //~ ERROR cannot find type `A` in this scope
-   |            ^ did you mean `I`?
+   |            ^ help: a type parameter with a similar name exists: `I`
 
 error: aborting due to previous error
 

src/test/ui/empty/empty-struct-braces-expr.stderr

@@ -4,17 +4,17 @@ error[E0423]: expected value, found struct `Empty1`
 LL |     let e1 = Empty1; //~ ERROR expected value, found struct `Empty1`
    |              ^^^^^^
    |              |
-   |              did you mean `XEmpty2`?
    |              did you mean `Empty1 { /* fields */ }`?
+   |              help: a unit struct with a similar name exists: `XEmpty2`
 
 error[E0423]: expected function, found struct `Empty1`
   --> $DIR/empty-struct-braces-expr.rs:16:14
    |
 LL |     let e1 = Empty1(); //~ ERROR expected function, found struct `Empty1`
    |              ^^^^^^
    |              |
-   |              did you mean `XEmpty2`?
    |              did you mean `Empty1 { /* fields */ }`?
+   |              help: a unit struct with a similar name exists: `XEmpty2`
 
 error[E0423]: expected value, found struct variant `E::Empty3`
   --> $DIR/empty-struct-braces-expr.rs:17:14
@@ -34,17 +34,17 @@ error[E0423]: expected value, found struct `XEmpty1`
 LL |     let xe1 = XEmpty1; //~ ERROR expected value, found struct `XEmpty1`
    |               ^^^^^^^
    |               |
-   |               did you mean `XEmpty2`?
    |               did you mean `XEmpty1 { /* fields */ }`?
+   |               help: a unit struct with a similar name exists: `XEmpty2`
 
 error[E0423]: expected function, found struct `XEmpty1`
   --> $DIR/empty-struct-braces-expr.rs:21:15
    |
 LL |     let xe1 = XEmpty1(); //~ ERROR expected function, found struct `XEmpty1`
    |               ^^^^^^^
    |               |
-   |               did you mean `XEmpty2`?
    |               did you mean `XEmpty1 { /* fields */ }`?
+   |               help: a unit struct with a similar name exists: `XEmpty2`
 
 error[E0599]: no variant named `Empty3` found for type `empty_struct::XE` in the current scope
   --> $DIR/empty-struct-braces-expr.rs:22:19

src/test/ui/empty/empty-struct-braces-pat-1.stderr

@@ -10,7 +10,7 @@ error[E0532]: expected unit struct/variant or constant, found struct variant `XE
 LL |         XE::XEmpty3 => ()
    |         ^^^^-------
    |         |   |
-   |         |   did you mean `XEmpty4`?
+   |         |   help: a unit variant with a similar name exists: `XEmpty4`
    |         did you mean `XE::XEmpty3 { /* fields */ }`?
 
 error: aborting due to 2 previous errors

src/test/ui/empty/empty-struct-braces-pat-2.stderr

@@ -4,35 +4,35 @@ error[E0532]: expected tuple struct/variant, found struct `Empty1`
 LL |         Empty1() => () //~ ERROR expected tuple struct/variant, found struct `Empty1`
    |         ^^^^^^
    |         |
-   |         did you mean `XEmpty6`?
    |         did you mean `Empty1 { /* fields */ }`?
+   |         help: a tuple struct with a similar name exists: `XEmpty6`
 
 error[E0532]: expected tuple struct/variant, found struct `XEmpty1`
   --> $DIR/empty-struct-braces-pat-2.rs:18:9
    |
 LL |         XEmpty1() => () //~ ERROR expected tuple struct/variant, found struct `XEmpty1`
    |         ^^^^^^^
    |         |
-   |         did you mean `XEmpty6`?
    |         did you mean `XEmpty1 { /* fields */ }`?
+   |         help: a tuple struct with a similar name exists: `XEmpty6`
 
 error[E0532]: expected tuple struct/variant, found struct `Empty1`
   --> $DIR/empty-struct-braces-pat-2.rs:21:9
    |
 LL |         Empty1(..) => () //~ ERROR expected tuple struct/variant, found struct `Empty1`
    |         ^^^^^^
    |         |
-   |         did you mean `XEmpty6`?
    |         did you mean `Empty1 { /* fields */ }`?
+   |         help: a tuple struct with a similar name exists: `XEmpty6`
 
 error[E0532]: expected tuple struct/variant, found struct `XEmpty1`
   --> $DIR/empty-struct-braces-pat-2.rs:24:9
    |
 LL |         XEmpty1(..) => () //~ ERROR expected tuple struct/variant, found struct `XEmpty1`
    |         ^^^^^^^
    |         |
-   |         did you mean `XEmpty6`?
    |         did you mean `XEmpty1 { /* fields */ }`?
+   |         help: a tuple struct with a similar name exists: `XEmpty6`
 
 error: aborting due to 4 previous errors
 

src/test/ui/empty/empty-struct-braces-pat-3.stderr

@@ -10,7 +10,7 @@ error[E0532]: expected tuple struct/variant, found struct variant `XE::XEmpty3`
 LL |         XE::XEmpty3() => ()
    |         ^^^^-------
    |         |   |
-   |         |   did you mean `XEmpty5`?
+   |         |   help: a tuple variant with a similar name exists: `XEmpty5`
    |         did you mean `XE::XEmpty3 { /* fields */ }`?
 
 error[E0532]: expected tuple struct/variant, found struct variant `E::Empty3`
@@ -25,7 +25,7 @@ error[E0532]: expected tuple struct/variant, found struct variant `XE::XEmpty3`
 LL |         XE::XEmpty3(..) => ()
    |         ^^^^-------
    |         |   |
-   |         |   did you mean `XEmpty5`?
+   |         |   help: a tuple variant with a similar name exists: `XEmpty5`
    |         did you mean `XE::XEmpty3 { /* fields */ }`?
 
 error: aborting due to 4 previous errors

src/test/ui/empty/empty-struct-tuple-pat.stderr

@@ -28,7 +28,7 @@ error[E0532]: expected unit struct/variant or constant, found tuple variant `XE:
 LL |         XE::XEmpty5 => (),
    |         ^^^^-------
    |             |
-   |             did you mean `XEmpty4`?
+   |             help: a unit variant with a similar name exists: `XEmpty4`
 
 error: aborting due to 4 previous errors
 

src/test/ui/empty/empty-struct-unit-pat.stderr

@@ -2,25 +2,25 @@ error[E0532]: expected tuple struct/variant, found unit struct `Empty2`
   --> $DIR/empty-struct-unit-pat.rs:21:9
    |
 LL |         Empty2() => () //~ ERROR expected tuple struct/variant, found unit struct `Empty2`
-   |         ^^^^^^ did you mean `XEmpty6`?
+   |         ^^^^^^ help: a tuple struct with a similar name exists: `XEmpty6`
 
 error[E0532]: expected tuple struct/variant, found unit struct `XEmpty2`
   --> $DIR/empty-struct-unit-pat.rs:24:9
    |
 LL |         XEmpty2() => () //~ ERROR expected tuple struct/variant, found unit struct `XEmpty2`
-   |         ^^^^^^^ did you mean `XEmpty6`?
+   |         ^^^^^^^ help: a tuple struct with a similar name exists: `XEmpty6`
 
 error[E0532]: expected tuple struct/variant, found unit struct `Empty2`
   --> $DIR/empty-struct-unit-pat.rs:27:9
    |
 LL |         Empty2(..) => () //~ ERROR expected tuple struct/variant, found unit struct `Empty2`
-   |         ^^^^^^ did you mean `XEmpty6`?
+   |         ^^^^^^ help: a tuple struct with a similar name exists: `XEmpty6`
 
 error[E0532]: expected tuple struct/variant, found unit struct `XEmpty2`
   --> $DIR/empty-struct-unit-pat.rs:30:9
    |
 LL |         XEmpty2(..) => () //~ ERROR expected tuple struct/variant, found unit struct `XEmpty2`
-   |         ^^^^^^^ did you mean `XEmpty6`?
+   |         ^^^^^^^ help: a tuple struct with a similar name exists: `XEmpty6`
 
 error[E0532]: expected tuple struct/variant, found unit variant `E::Empty4`
   --> $DIR/empty-struct-unit-pat.rs:34:9
@@ -34,7 +34,7 @@ error[E0532]: expected tuple struct/variant, found unit variant `XE::XEmpty4`
 LL |         XE::XEmpty4() => (),
    |         ^^^^-------
    |             |
-   |             did you mean `XEmpty5`?
+   |             help: a tuple variant with a similar name exists: `XEmpty5`
 
 error[E0532]: expected tuple struct/variant, found unit variant `E::Empty4`
   --> $DIR/empty-struct-unit-pat.rs:42:9
@@ -48,7 +48,7 @@ error[E0532]: expected tuple struct/variant, found unit variant `XE::XEmpty4`
 LL |         XE::XEmpty4(..) => (),
    |         ^^^^-------
    |             |
-   |             did you mean `XEmpty5`?
+   |             help: a tuple variant with a similar name exists: `XEmpty5`
 
 error: aborting due to 8 previous errors
 

src/test/ui/error-codes/E0423.stderr

@@ -22,8 +22,8 @@ error[E0423]: expected function, found struct `Foo`
 LL |     let f = Foo(); //~ ERROR E0423
    |             ^^^
    |             |
-   |             did you mean `foo`?
    |             did you mean `Foo { /* fields */ }`?
+   |             help: a function with a similar name exists: `foo`
 
 error[E0423]: expected value, found struct `S`
   --> $DIR/E0423.rs:12:32

src/test/ui/error-festival.stderr

@@ -2,7 +2,7 @@ error[E0425]: cannot find value `y` in this scope
   --> $DIR/error-festival.rs:14:5
    |
 LL |     y = 2;
-   |     ^ did you mean `x`?
+   |     ^ help: a local variable with a similar name exists: `x`
 
 error[E0603]: constant `FOO` is private
   --> $DIR/error-festival.rs:22:10