Improve the "try using a variant of the expected type" hint.

Patryk27 · Patryk27 · commit 273ee611f08e · 2019-10-28T18:43:51.000+01:00
diff --git a/src/librustc/hir/print.rs b/src/librustc/hir/print.rs
@@ -1523,9 +1523,7 @@ impl<'a> State<'a> {
                                         colons_before_params)
             }
             hir::QPath::TypeRelative(ref qself, ref item_segment) => {
-                self.s.word("<");
                 self.print_type(qself);
-                self.s.word(">");
                 self.s.word("::");
                 self.print_ident(item_segment.ident);
                 self.print_generic_args(item_segment.generic_args(),
diff --git a/src/librustc_typeck/check/demand.rs b/src/librustc_typeck/check/demand.rs
@@ -172,10 +172,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }).peekable();
 
             if compatible_variants.peek().is_some() {
-                let expr_text = print::to_string(print::NO_ANN, |s| s.print_expr(expr));
+                let expr_text = self.tcx.sess
+                    .source_map()
+                    .span_to_snippet(expr.span)
+                    .unwrap_or_else(|_| {
+                        print::to_string(print::NO_ANN, |s| s.print_expr(expr))
+                    });
                 let suggestions = compatible_variants
                     .map(|v| format!("{}({})", v, expr_text));
-                let msg = "try using a variant of the expected type";
+                let msg = "try using a variant of the expected enum";
                 err.span_suggestions(expr.span, msg, suggestions, Applicability::MaybeIncorrect);
             }
         }
diff --git a/src/test/ui/did_you_mean/issue-42764.rs b/src/test/ui/did_you_mean/issue-42764.rs
@@ -10,7 +10,7 @@ fn main() {
     let n: usize = 42;
     this_function_expects_a_double_option(n);
     //~^ ERROR mismatched types
-    //~| HELP try using a variant of the expected type
+    //~| HELP try using a variant of the expected enum
 }
 
 
diff --git a/src/test/ui/did_you_mean/issue-42764.stderr b/src/test/ui/did_you_mean/issue-42764.stderr
@@ -6,7 +6,7 @@ LL |     this_function_expects_a_double_option(n);
    |
    = note: expected type `DoubleOption<_>`
               found type `usize`
-help: try using a variant of the expected type
+help: try using a variant of the expected enum
    |
 LL |     this_function_expects_a_double_option(DoubleOption::FirstSome(n));
    |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/error-codes/E0164.stderr b/src/test/ui/error-codes/E0164.stderr
@@ -1,4 +1,4 @@
-error[E0164]: expected tuple struct or tuple variant, found associated constant `<Foo>::B`
+error[E0164]: expected tuple struct or tuple variant, found associated constant `Foo::B`
   --> $DIR/E0164.rs:9:9
    |
 LL |         Foo::B(i) => i,
diff --git a/src/test/ui/fn-in-pat.stderr b/src/test/ui/fn-in-pat.stderr
@@ -1,4 +1,4 @@
-error[E0164]: expected tuple struct or tuple variant, found method `<A>::new`
+error[E0164]: expected tuple struct or tuple variant, found method `A::new`
   --> $DIR/fn-in-pat.rs:11:9
    |
 LL |         A::new() => (),
diff --git a/src/test/ui/fully-qualified-type/fully-qualified-type-name1.stderr b/src/test/ui/fully-qualified-type/fully-qualified-type-name1.stderr
@@ -5,7 +5,7 @@ LL |     x = 5;
    |         ^
    |         |
    |         expected enum `std::option::Option`, found integer
-   |         help: try using a variant of the expected type: `Some(5)`
+   |         help: try using a variant of the expected enum: `Some(5)`
    |
    = note: expected type `std::option::Option<usize>`
               found type `{integer}`
diff --git a/src/test/ui/issues/issue-28992-empty.rs b/src/test/ui/issues/issue-28992-empty.rs
@@ -12,5 +12,5 @@ impl S {
 fn main() {
     if let C1(..) = 0 {} //~ ERROR expected tuple struct or tuple variant, found constant `C1`
     if let S::C2(..) = 0 {}
-    //~^ ERROR expected tuple struct or tuple variant, found associated constant `<S>::C2`
+    //~^ ERROR expected tuple struct or tuple variant, found associated constant `S::C2`
 }
diff --git a/src/test/ui/issues/issue-28992-empty.stderr b/src/test/ui/issues/issue-28992-empty.stderr
@@ -4,7 +4,7 @@ error[E0532]: expected tuple struct or tuple variant, found constant `C1`
 LL |     if let C1(..) = 0 {}
    |            ^^ not a tuple struct or tuple variant
 
-error[E0164]: expected tuple struct or tuple variant, found associated constant `<S>::C2`
+error[E0164]: expected tuple struct or tuple variant, found associated constant `S::C2`
   --> $DIR/issue-28992-empty.rs:14:12
    |
 LL |     if let S::C2(..) = 0 {}
diff --git a/src/test/ui/issues/issue-46112.stderr b/src/test/ui/issues/issue-46112.stderr
@@ -5,7 +5,7 @@ LL | fn main() { test(Ok(())); }
    |                     ^^
    |                     |
    |                     expected enum `std::option::Option`, found ()
-   |                     help: try using a variant of the expected type: `Some(())`
+   |                     help: try using a variant of the expected enum: `Some(())`
    |
    = note: expected type `std::option::Option<()>`
               found type `()`
diff --git a/src/test/ui/issues/issue-55587.stderr b/src/test/ui/issues/issue-55587.stderr
@@ -1,4 +1,4 @@
-error[E0164]: expected tuple struct or tuple variant, found method `<Path>::new`
+error[E0164]: expected tuple struct or tuple variant, found method `Path::new`
   --> $DIR/issue-55587.rs:4:9
    |
 LL |     let Path::new();
diff --git a/src/test/ui/match/match-fn-call.stderr b/src/test/ui/match/match-fn-call.stderr
@@ -1,12 +1,12 @@
-error[E0164]: expected tuple struct or tuple variant, found method `<Path>::new`
+error[E0164]: expected tuple struct or tuple variant, found method `Path::new`
   --> $DIR/match-fn-call.rs:6:9
    |
 LL |         Path::new("foo") => println!("foo"),
    |         ^^^^^^^^^^^^^^^^ `fn` calls are not allowed in patterns
    |
    = help: for more information, visit https://doc.rust-lang.org/book/ch18-00-patterns.html
 
-error[E0164]: expected tuple struct or tuple variant, found method `<Path>::new`
+error[E0164]: expected tuple struct or tuple variant, found method `Path::new`
   --> $DIR/match-fn-call.rs:8:9
    |
 LL |         Path::new("bar") => println!("bar"),
diff --git a/src/test/ui/methods/method-path-in-pattern.rs b/src/test/ui/methods/method-path-in-pattern.rs
@@ -13,20 +13,20 @@ impl MyTrait for Foo {}
 fn main() {
     match 0u32 {
         Foo::bar => {}
-        //~^ ERROR expected unit struct, unit variant or constant, found method `<Foo>::bar`
+        //~^ ERROR expected unit struct, unit variant or constant, found method `Foo::bar`
     }
     match 0u32 {
         <Foo>::bar => {}
-        //~^ ERROR expected unit struct, unit variant or constant, found method `<Foo>::bar`
+        //~^ ERROR expected unit struct, unit variant or constant, found method `Foo::bar`
     }
     match 0u32 {
         <Foo>::trait_bar => {}
-        //~^ ERROR expected unit struct, unit variant or constant, found method `<Foo>::trait_bar`
+        //~^ ERROR expected unit struct, unit variant or constant, found method `Foo::trait_bar`
     }
     if let Foo::bar = 0u32 {}
-    //~^ ERROR expected unit struct, unit variant or constant, found method `<Foo>::bar`
+    //~^ ERROR expected unit struct, unit variant or constant, found method `Foo::bar`
     if let <Foo>::bar = 0u32 {}
-    //~^ ERROR expected unit struct, unit variant or constant, found method `<Foo>::bar`
+    //~^ ERROR expected unit struct, unit variant or constant, found method `Foo::bar`
     if let Foo::trait_bar = 0u32 {}
-    //~^ ERROR expected unit struct, unit variant or constant, found method `<Foo>::trait_bar`
+    //~^ ERROR expected unit struct, unit variant or constant, found method `Foo::trait_bar`
 }
diff --git a/src/test/ui/methods/method-path-in-pattern.stderr b/src/test/ui/methods/method-path-in-pattern.stderr
@@ -1,34 +1,34 @@
-error[E0533]: expected unit struct, unit variant or constant, found method `<Foo>::bar`
+error[E0533]: expected unit struct, unit variant or constant, found method `Foo::bar`
   --> $DIR/method-path-in-pattern.rs:15:9
    |
 LL |         Foo::bar => {}
    |         ^^^^^^^^
 
-error[E0533]: expected unit struct, unit variant or constant, found method `<Foo>::bar`
+error[E0533]: expected unit struct, unit variant or constant, found method `Foo::bar`
   --> $DIR/method-path-in-pattern.rs:19:9
    |
 LL |         <Foo>::bar => {}
    |         ^^^^^^^^^^
 
-error[E0533]: expected unit struct, unit variant or constant, found method `<Foo>::trait_bar`
+error[E0533]: expected unit struct, unit variant or constant, found method `Foo::trait_bar`
   --> $DIR/method-path-in-pattern.rs:23:9
    |
 LL |         <Foo>::trait_bar => {}
    |         ^^^^^^^^^^^^^^^^
 
-error[E0533]: expected unit struct, unit variant or constant, found method `<Foo>::bar`
+error[E0533]: expected unit struct, unit variant or constant, found method `Foo::bar`
   --> $DIR/method-path-in-pattern.rs:26:12
    |
 LL |     if let Foo::bar = 0u32 {}
    |            ^^^^^^^^
 
-error[E0533]: expected unit struct, unit variant or constant, found method `<Foo>::bar`
+error[E0533]: expected unit struct, unit variant or constant, found method `Foo::bar`
   --> $DIR/method-path-in-pattern.rs:28:12
    |
 LL |     if let <Foo>::bar = 0u32 {}
    |            ^^^^^^^^^^
 
-error[E0533]: expected unit struct, unit variant or constant, found method `<Foo>::trait_bar`
+error[E0533]: expected unit struct, unit variant or constant, found method `Foo::trait_bar`
   --> $DIR/method-path-in-pattern.rs:30:12
    |
 LL |     if let Foo::trait_bar = 0u32 {}
diff --git a/src/test/ui/qualified/qualified-path-params.rs b/src/test/ui/qualified/qualified-path-params.rs
@@ -18,7 +18,7 @@ impl S {
 fn main() {
     match 10 {
         <S as Tr>::A::f::<u8> => {}
-    //~^ ERROR expected unit struct, unit variant or constant, found method `<<S as Tr>::A>::f<u8>`
+    //~^ ERROR expected unit struct, unit variant or constant, found method `<S as Tr>::A::f<u8>`
         0 ..= <S as Tr>::A::f::<u8> => {} //~ ERROR only char and numeric types are allowed in range
     }
 }
diff --git a/src/test/ui/qualified/qualified-path-params.stderr b/src/test/ui/qualified/qualified-path-params.stderr
@@ -1,4 +1,4 @@
-error[E0533]: expected unit struct, unit variant or constant, found method `<<S as Tr>::A>::f<u8>`
+error[E0533]: expected unit struct, unit variant or constant, found method `<S as Tr>::A::f<u8>`
   --> $DIR/qualified-path-params.rs:20:9
    |
 LL |         <S as Tr>::A::f::<u8> => {}
diff --git a/src/test/ui/type-alias-enum-variants/incorrect-variant-form-through-Self-issue-58006.stderr b/src/test/ui/type-alias-enum-variants/incorrect-variant-form-through-Self-issue-58006.stderr
@@ -1,4 +1,4 @@
-error[E0533]: expected unit struct, unit variant or constant, found tuple variant `<Self>::A`
+error[E0533]: expected unit struct, unit variant or constant, found tuple variant `Self::A`
   --> $DIR/incorrect-variant-form-through-Self-issue-58006.rs:8:13
    |
 LL |             Self::A => (),
diff --git a/src/test/ui/type-alias-enum-variants/incorrect-variant-form-through-alias-caught.rs b/src/test/ui/type-alias-enum-variants/incorrect-variant-form-through-alias-caught.rs
@@ -8,14 +8,14 @@ type Alias = Enum;
 
 fn main() {
     Alias::Braced;
-    //~^ ERROR expected unit struct, unit variant or constant, found struct variant `<Alias>::Braced` [E0533]
+    //~^ ERROR expected unit struct, unit variant or constant, found struct variant `Alias::Braced` [E0533]
     let Alias::Braced = panic!();
-    //~^ ERROR expected unit struct, unit variant or constant, found struct variant `<Alias>::Braced` [E0533]
+    //~^ ERROR expected unit struct, unit variant or constant, found struct variant `Alias::Braced` [E0533]
     let Alias::Braced(..) = panic!();
-    //~^ ERROR expected tuple struct or tuple variant, found struct variant `<Alias>::Braced` [E0164]
+    //~^ ERROR expected tuple struct or tuple variant, found struct variant `Alias::Braced` [E0164]
 
     Alias::Unit();
-    //~^ ERROR expected function, found enum variant `<Alias>::Unit`
+    //~^ ERROR expected function, found enum variant `Alias::Unit`
     let Alias::Unit() = panic!();
-    //~^ ERROR expected tuple struct or tuple variant, found unit variant `<Alias>::Unit` [E0164]
+    //~^ ERROR expected tuple struct or tuple variant, found unit variant `Alias::Unit` [E0164]
 }
diff --git a/src/test/ui/type-alias-enum-variants/incorrect-variant-form-through-alias-caught.stderr b/src/test/ui/type-alias-enum-variants/incorrect-variant-form-through-alias-caught.stderr
@@ -1,38 +1,38 @@
-error[E0533]: expected unit struct, unit variant or constant, found struct variant `<Alias>::Braced`
+error[E0533]: expected unit struct, unit variant or constant, found struct variant `Alias::Braced`
   --> $DIR/incorrect-variant-form-through-alias-caught.rs:10:5
    |
 LL |     Alias::Braced;
    |     ^^^^^^^^^^^^^
 
-error[E0533]: expected unit struct, unit variant or constant, found struct variant `<Alias>::Braced`
+error[E0533]: expected unit struct, unit variant or constant, found struct variant `Alias::Braced`
   --> $DIR/incorrect-variant-form-through-alias-caught.rs:12:9
    |
 LL |     let Alias::Braced = panic!();
    |         ^^^^^^^^^^^^^
 
-error[E0164]: expected tuple struct or tuple variant, found struct variant `<Alias>::Braced`
+error[E0164]: expected tuple struct or tuple variant, found struct variant `Alias::Braced`
   --> $DIR/incorrect-variant-form-through-alias-caught.rs:14:9
    |
 LL |     let Alias::Braced(..) = panic!();
    |         ^^^^^^^^^^^^^^^^^ not a tuple variant or struct
 
-error[E0618]: expected function, found enum variant `<Alias>::Unit`
+error[E0618]: expected function, found enum variant `Alias::Unit`
   --> $DIR/incorrect-variant-form-through-alias-caught.rs:17:5
    |
 LL | enum Enum { Braced {}, Unit, Tuple() }
-   |                        ---- `<Alias>::Unit` defined here
+   |                        ---- `Alias::Unit` defined here
 ...
 LL |     Alias::Unit();
    |     ^^^^^^^^^^^--
    |     |
    |     call expression requires function
    |
-help: `<Alias>::Unit` is a unit variant, you need to write it without the parenthesis
+help: `Alias::Unit` is a unit variant, you need to write it without the parenthesis
    |
-LL |     <Alias>::Unit;
-   |     ^^^^^^^^^^^^^
+LL |     Alias::Unit;
+   |     ^^^^^^^^^^^
 
-error[E0164]: expected tuple struct or tuple variant, found unit variant `<Alias>::Unit`
+error[E0164]: expected tuple struct or tuple variant, found unit variant `Alias::Unit`
   --> $DIR/incorrect-variant-form-through-alias-caught.rs:19:9
    |
 LL |     let Alias::Unit() = panic!();

Original file line number	Diff line number	Diff line change
`@@ -10,7 +10,7 @@ fn main() {`
`10`	`10`	`let n: usize = 42;`
`11`	`11`	`this_function_expects_a_double_option(n);`
`12`	`12`	`//~^ ERROR mismatched types`
`13`		`- //~\| HELP try using a variant of the expected type`
	`13`	`+ //~\| HELP try using a variant of the expected enum`
`14`	`14`	`}`
`15`	`15`
`16`	`16`
Original file line number	Diff line number	Diff line change
`@@ -6,7 +6,7 @@ LL \| this_function_expects_a_double_option(n);`
`6`	`6`	`\|`
`7`	`7`	= note: expected type `DoubleOption<_>`
`8`	`8`	found type `usize`
`9`		`-help: try using a variant of the expected type`
	`9`	`+help: try using a variant of the expected enum`
`10`	`10`	`\|`
`11`	`11`	`LL \| this_function_expects_a_double_option(DoubleOption::FirstSome(n));`
`12`	`12`	`\| ^^^^^^^^^^^^^^^^^^^^^^^^^^`
Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		-error[E0164]: expected tuple struct or tuple variant, found associated constant `<Foo>::B`
	`1`	+error[E0164]: expected tuple struct or tuple variant, found associated constant `Foo::B`
`2`	`2`	`--> $DIR/E0164.rs:9:9`
`3`	`3`	`\|`
`4`	`4`	`LL \| Foo::B(i) => i,`
Original file line number	Diff line number	Diff line change
`@@ -5,7 +5,7 @@ LL \| x = 5;`
`5`	`5`	`\| ^`
`6`	`6`	`\| \|`
`7`	`7`	\| expected enum `std::option::Option`, found integer
`8`		- \| help: try using a variant of the expected type: `Some(5)`
	`8`	+ \| help: try using a variant of the expected enum: `Some(5)`
`9`	`9`	`\|`
`10`	`10`	= note: expected type `std::option::Option<usize>`
`11`	`11`	found type `{integer}`
Original file line number	Diff line number	Diff line change
`@@ -12,5 +12,5 @@ impl S {`
`12`	`12`	`fn main() {`
`13`	`13`	if let C1(..) = 0 {} //~ ERROR expected tuple struct or tuple variant, found constant `C1`
`14`	`14`	`if let S::C2(..) = 0 {}`
`15`		- //~^ ERROR expected tuple struct or tuple variant, found associated constant `<S>::C2`
	`15`	+ //~^ ERROR expected tuple struct or tuple variant, found associated constant `S::C2`
`16`	`16`	`}`
Original file line number	Diff line number	Diff line change
@@ -4,7 +4,7 @@ error[E0532]: expected tuple struct or tuple variant, found constant `C1`
`4`	`4`	`LL \| if let C1(..) = 0 {}`
`5`	`5`	`\| ^^ not a tuple struct or tuple variant`
`6`	`6`
`7`		-error[E0164]: expected tuple struct or tuple variant, found associated constant `<S>::C2`
	`7`	+error[E0164]: expected tuple struct or tuple variant, found associated constant `S::C2`
`8`	`8`	`--> $DIR/issue-28992-empty.rs:14:12`
`9`	`9`	`\|`
`10`	`10`	`LL \| if let S::C2(..) = 0 {}`
Original file line number	Diff line number	Diff line change
`@@ -5,7 +5,7 @@ LL \| fn main() { test(Ok(())); }`
`5`	`5`	`\| ^^`
`6`	`6`	`\| \|`
`7`	`7`	\| expected enum `std::option::Option`, found ()
`8`		- \| help: try using a variant of the expected type: `Some(())`
	`8`	+ \| help: try using a variant of the expected enum: `Some(())`
`9`	`9`	`\|`
`10`	`10`	= note: expected type `std::option::Option<()>`
`11`	`11`	found type `()`