Suggest usage of angle brackets

estebank · estebank · commit d37a6d83e162 · 2019-01-19T19:39:58.000-08:00
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
@@ -31,6 +31,7 @@
 //! in the HIR, especially for multiple identifiers.
 
 use dep_graph::DepGraph;
+use errors::Applicability;
 use hir::{self, ParamName};
 use hir::HirVec;
 use hir::map::{DefKey, DefPathData, Definitions};
@@ -1823,9 +1824,17 @@ impl<'a> LoweringContext<'a> {
                         (hir::GenericArgs::none(), true)
                     }
                     ParenthesizedGenericArgs::Err => {
-                        struct_span_err!(self.sess, data.span, E0214, "{}", msg)
-                            .span_label(data.span, "only traits may use parentheses")
-                            .emit();
+                        let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
+                        err.span_label(data.span, "only traits may use parentheses");
+                        if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
+                            err.span_suggestion_with_applicability(
+                                data.span,
+                                "use angle brackets instead",
+                                format!("<{}>", &snippet[1..snippet.len() - 1]),
+                                Applicability::MaybeIncorrect,
+                            );
+                        };
+                        err.emit();
                         (self.lower_angle_bracketed_parameter_data(
                             &data.as_angle_bracketed_args(),
                             param_mode,
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
@@ -2176,11 +2176,11 @@ impl<'a> Parser<'a> {
               style != PathStyle::Mod && self.check(&token::ModSep)
                                       && self.look_ahead(1, |t| is_args_start(t)) {
             // Generic arguments are found - `<`, `(`, `::<` or `::(`.
-            let lo = self.span;
             if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning {
                 self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator")
                                  .span_label(self.prev_span, "try removing `::`").emit();
             }
+            let lo = self.span;
 
             let args = if self.eat_lt() {
                 // `<'a, T, A = U>`
diff --git a/src/test/ui/error-codes/E0214.stderr b/src/test/ui/error-codes/E0214.stderr
@@ -2,7 +2,10 @@ error[E0214]: parenthesized parameters may only be used with a trait
   --> $DIR/E0214.rs:2:15
    |
 LL |     let v: Vec(&str) = vec!["foo"];
-   |               ^^^^^^ only traits may use parentheses
+   |               ^^^^^^
+   |               |
+   |               only traits may use parentheses
+   |               help: use angle brackets instead: `<&str>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-23589.stderr b/src/test/ui/issues/issue-23589.stderr
@@ -2,7 +2,10 @@ error[E0214]: parenthesized parameters may only be used with a trait
   --> $DIR/issue-23589.rs:2:15
    |
 LL |     let v: Vec(&str) = vec!['1', '2'];
-   |               ^^^^^^ only traits may use parentheses
+   |               ^^^^^^
+   |               |
+   |               only traits may use parentheses
+   |               help: use angle brackets instead: `<&str>`
 
 error[E0308]: mismatched types
   --> $DIR/issue-23589.rs:2:29
diff --git a/src/test/ui/issues/issue-32995.stderr b/src/test/ui/issues/issue-32995.stderr
@@ -18,19 +18,19 @@ LL |     let b: ::std::boxed()::Box<_> = Box::new(1);
    = note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>
 
 error: parenthesized parameters may only be used with a trait
-  --> $DIR/issue-32995.rs:12:23
+  --> $DIR/issue-32995.rs:12:25
    |
 LL |     let p = ::std::str::()::from_utf8(b"foo").unwrap();
-   |                       ^^^^
+   |                         ^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>
 
 error: parenthesized parameters may only be used with a trait
-  --> $DIR/issue-32995.rs:16:34
+  --> $DIR/issue-32995.rs:16:36
    |
 LL |     let p = ::std::str::from_utf8::()(b"foo").unwrap();
-   |                                  ^^^^
+   |                                    ^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>
diff --git a/src/test/ui/parser/type-parameters-in-field-exprs.stderr b/src/test/ui/parser/type-parameters-in-field-exprs.stderr
@@ -1,20 +1,20 @@
 error: field expressions may not have generic arguments
-  --> $DIR/type-parameters-in-field-exprs.rs:13:8
+  --> $DIR/type-parameters-in-field-exprs.rs:13:10
    |
 LL |     f.x::<isize>;
-   |        ^^^^^^^^^
+   |          ^^^^^^^
 
 error: field expressions may not have generic arguments
-  --> $DIR/type-parameters-in-field-exprs.rs:15:8
+  --> $DIR/type-parameters-in-field-exprs.rs:15:10
    |
 LL |     f.x::<>;
-   |        ^^^^
+   |          ^^
 
 error: field expressions may not have generic arguments
-  --> $DIR/type-parameters-in-field-exprs.rs:17:8
+  --> $DIR/type-parameters-in-field-exprs.rs:17:10
    |
 LL |     f.x::();
-   |        ^^^^
+   |          ^^
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/span/macro-ty-params.stderr b/src/test/ui/span/macro-ty-params.stderr
@@ -1,14 +1,14 @@
 error: generic arguments in macro path
-  --> $DIR/macro-ty-params.rs:10:8
+  --> $DIR/macro-ty-params.rs:10:10
    |
 LL |     foo::<T>!(); //~ ERROR generic arguments in macro path
-   |        ^^^^^
+   |          ^^^
 
 error: generic arguments in macro path
-  --> $DIR/macro-ty-params.rs:11:8
+  --> $DIR/macro-ty-params.rs:11:10
    |
 LL |     foo::<>!(); //~ ERROR generic arguments in macro path
-   |        ^^^^
+   |          ^^
 
 error: unexpected generic arguments in path
   --> $DIR/macro-ty-params.rs:12:8
diff --git a/src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct-1.stderr b/src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct-1.stderr
@@ -2,7 +2,10 @@ error[E0214]: parenthesized parameters may only be used with a trait
   --> $DIR/unboxed-closure-sugar-used-on-struct-1.rs:8:19
    |
 LL |     let x: Box<Bar()> = panic!();
-   |                   ^^ only traits may use parentheses
+   |                   ^^
+   |                   |
+   |                   only traits may use parentheses
+   |                   help: use angle brackets instead: `<>`
 
 error[E0107]: wrong number of type arguments: expected 1, found 0
   --> $DIR/unboxed-closure-sugar-used-on-struct-1.rs:8:16
diff --git a/src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct-3.stderr b/src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct-3.stderr
@@ -1,8 +1,11 @@
 error[E0214]: parenthesized parameters may only be used with a trait
-  --> $DIR/unboxed-closure-sugar-used-on-struct-3.rs:14:16
+  --> $DIR/unboxed-closure-sugar-used-on-struct-3.rs:14:18
    |
 LL |     let b = Bar::(isize, usize)::new(); // OK too (for the parser)
-   |                ^^^^^^^^^^^^^^^^ only traits may use parentheses
+   |                  ^^^^^^^^^^^^^^
+   |                  |
+   |                  only traits may use parentheses
+   |                  help: use angle brackets instead: `<isize, usize>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct.stderr b/src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct.stderr
@@ -2,7 +2,10 @@ error[E0214]: parenthesized parameters may only be used with a trait
   --> $DIR/unboxed-closure-sugar-used-on-struct.rs:7:18
    |
 LL | fn foo(b: Box<Bar()>) {
-   |                  ^^ only traits may use parentheses
+   |                  ^^
+   |                  |
+   |                  only traits may use parentheses
+   |                  help: use angle brackets instead: `<>`
 
 error[E0107]: wrong number of type arguments: expected 1, found 0
   --> $DIR/unboxed-closure-sugar-used-on-struct.rs:7:15

Original file line number	Diff line number	Diff line change
`@@ -18,19 +18,19 @@ LL \| let b: ::std::boxed()::Box<_> = Box::new(1);`
`18`	`18`	`= note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>`
`19`	`19`
`20`	`20`	`error: parenthesized parameters may only be used with a trait`
`21`		`- --> $DIR/issue-32995.rs:12:23`
	`21`	`+ --> $DIR/issue-32995.rs:12:25`
`22`	`22`	`\|`
`23`	`23`	`LL \| let p = ::std::str::()::from_utf8(b"foo").unwrap();`
`24`		`- \| ^^^^`
	`24`	`+ \| ^^`
`25`	`25`	`\|`
`26`	`26`	`= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!`
`27`	`27`	`= note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>`
`28`	`28`
`29`	`29`	`error: parenthesized parameters may only be used with a trait`
`30`		`- --> $DIR/issue-32995.rs:16:34`
	`30`	`+ --> $DIR/issue-32995.rs:16:36`
`31`	`31`	`\|`
`32`	`32`	`LL \| let p = ::std::str::from_utf8::()(b"foo").unwrap();`
`33`		`- \| ^^^^`
	`33`	`+ \| ^^`
`34`	`34`	`\|`
`35`	`35`	`= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!`
`36`	`36`	`= note: for more information, see issue #42238 <https://github.com/rust-lang/rust/issues/42238>`