Don't naively point to return type on type error

estebank · estebank · commit c13a913e5b41 · 2017-06-24T19:28:43.000-07:00
diff --git a/src/librustc_typeck/check/coercion.rs b/src/librustc_typeck/check/coercion.rs
@@ -1174,12 +1174,6 @@ impl<'gcx, 'tcx, 'exprs, E> CoerceMany<'gcx, 'tcx, 'exprs, E>
                                                              expected, found,
                                                              cause.span, blk_id);
                     }
-                    ObligationCauseCode::ReturnType(ret_id) => {
-                        db = fcx.report_mismatched_types(cause, expected, found, err);
-                        if let Some((fn_decl, _)) = fcx.get_fn_decl(ret_id) {
-                            fcx.point_to_type_requirement(&mut db, &fn_decl, expected);
-                        }
-                    }
                     _ => {
                         db = fcx.report_mismatched_types(cause, expected, found, err);
                     }
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
@@ -4261,35 +4261,13 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         self.suggest_missing_semicolon(err, expression, expected, cause_span);
 
         if let Some((fn_decl, is_main)) = self.get_fn_decl(blk_id) {
-            self.point_to_type_requirement(err, &fn_decl, expected);
             // `fn main()` must return `()`, do not suggest changing return type
             if !is_main {
                 self.suggest_missing_return_type(err, &fn_decl, found);
             }
         }
     }
 
-    pub fn point_to_type_requirement(&self,
-                                 err: &mut DiagnosticBuilder<'tcx>,
-                                 fn_decl: &hir::FnDecl,
-                                 ty: Ty<'tcx>) {
-        let msg = if let &hir::FnDecl {
-            output: hir::FunctionRetTy::DefaultReturn(_), ..
-        } = fn_decl {
-            "default "
-        } else {
-            ""
-        };
-        let ty = self.resolve_type_vars_if_possible(&ty);
-        if ty.to_string().len() < 10 {
-            err.span_label(fn_decl.output.span(),
-                           format!("expected `{}` because of this {}return type", ty, msg));
-        } else {
-            err.span_label(fn_decl.output.span(),
-                           format!("expected because of this {}return type", msg));
-        }
-    }
-
     /// A common error is to forget to add a semicolon at the end of a block:
     ///
     /// ```
diff --git a/src/test/ui/block-result/issue-13624.stderr b/src/test/ui/block-result/issue-13624.stderr
@@ -1,8 +1,6 @@
 error[E0308]: mismatched types
   --> $DIR/issue-13624.rs:17:5
    |
-16 |   pub fn get_enum_struct_variant() -> () {
-   |                                       -- expected `()` because of this return type
 17 |     Enum::EnumStructVariant { x: 1, y: 2, z: 3 }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found enum `a::Enum`
    |
diff --git a/src/test/ui/block-result/issue-20862.stderr b/src/test/ui/block-result/issue-20862.stderr
@@ -2,10 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-20862.rs:12:5
    |
 11 | fn foo(x: i32) {
-   |                -
-   |                |
-   |                possibly return type missing here?
-   |                expected `()` because of this default return type
+   |                - possibly return type missing here?
 12 |     |y| x + y
    |     ^^^^^^^^^ expected (), found closure
    |
diff --git a/src/test/ui/block-result/issue-22645.stderr b/src/test/ui/block-result/issue-22645.stderr
@@ -11,9 +11,6 @@ error[E0277]: the trait bound `{integer}: Scalar` is not satisfied
 error[E0308]: mismatched types
   --> $DIR/issue-22645.rs:25:3
    |
-23 | fn main() {
-   |           - expected `()` because of this default return type
-24 |   let b = Bob + 3.5;
 25 |   b + 3 //~ ERROR E0277
    |   ^^^^^ expected (), found struct `Bob`
    |
diff --git a/src/test/ui/block-result/issue-3563.stderr b/src/test/ui/block-result/issue-3563.stderr
@@ -8,10 +8,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-3563.rs:13:9
    |
 12 |     fn a(&self) {
-   |                 -
-   |                 |
-   |                 possibly return type missing here?
-   |                 expected `()` because of this default return type
+   |                 - possibly return type missing here?
 13 |         || self.b()
    |         ^^^^^^^^^^^ expected (), found closure
    |
diff --git a/src/test/ui/block-result/issue-5500.stderr b/src/test/ui/block-result/issue-5500.stderr
@@ -1,8 +1,6 @@
 error[E0308]: mismatched types
   --> $DIR/issue-5500.rs:12:5
    |
-11 | fn main() {
-   |           - expected `()` because of this default return type
 12 |     &panic!()
    |     ^^^^^^^^^ expected (), found reference
    |
diff --git a/src/test/ui/block-result/unexpected-return-on-unit.stderr b/src/test/ui/block-result/unexpected-return-on-unit.stderr
@@ -1,8 +1,6 @@
 error[E0308]: mismatched types
   --> $DIR/unexpected-return-on-unit.rs:19:5
    |
-18 | fn bar() {
-   |          - expected `()` because of this default return type
 19 |     foo()
    |     ^^^^^ expected (), found usize
    |
diff --git a/src/test/ui/impl-trait/equality.stderr b/src/test/ui/impl-trait/equality.stderr
@@ -1,9 +1,6 @@
 error[E0308]: mismatched types
   --> $DIR/equality.rs:25:5
    |
-21 | fn two(x: bool) -> impl Foo {
-   |                    -------- expected `i32` because of this return type
-...
 25 |     0_u32
    |     ^^^^^ expected i32, found u32
    |
diff --git a/src/test/ui/mismatched_types/abridged.stderr b/src/test/ui/mismatched_types/abridged.stderr
@@ -1,8 +1,6 @@
 error[E0308]: mismatched types
   --> $DIR/abridged.rs:26:5
    |
-25 | fn a() -> Foo {
-   |           --- expected `Foo` because of this return type
 26 |     Some(Foo { bar: 1 })
    |     ^^^^^^^^^^^^^^^^^^^^ expected struct `Foo`, found enum `std::option::Option`
    |
@@ -12,8 +10,6 @@ error[E0308]: mismatched types
 error[E0308]: mismatched types
   --> $DIR/abridged.rs:30:5
    |
-29 | fn a2() -> Foo {
-   |            --- expected `Foo` because of this return type
 30 |     Ok(Foo { bar: 1})
    |     ^^^^^^^^^^^^^^^^^ expected struct `Foo`, found enum `std::result::Result`
    |
@@ -23,8 +19,6 @@ error[E0308]: mismatched types
 error[E0308]: mismatched types
   --> $DIR/abridged.rs:34:5
    |
-33 | fn b() -> Option<Foo> {
-   |           ----------- expected because of this return type
 34 |     Foo { bar: 1 }
    |     ^^^^^^^^^^^^^^ expected enum `std::option::Option`, found struct `Foo`
    |
@@ -34,8 +28,6 @@ error[E0308]: mismatched types
 error[E0308]: mismatched types
   --> $DIR/abridged.rs:38:5
    |
-37 | fn c() -> Result<Foo, Bar> {
-   |           ---------------- expected because of this return type
 38 |     Foo { bar: 1 }
    |     ^^^^^^^^^^^^^^ expected enum `std::result::Result`, found struct `Foo`
    |
@@ -45,8 +37,6 @@ error[E0308]: mismatched types
 error[E0308]: mismatched types
   --> $DIR/abridged.rs:42:5
    |
-41 |   fn d() -> X<X<String, String>, String> {
-   |             ---------------------------- expected because of this return type
 42 | /     X {
 43 | |         x: X {
 44 | |             x: "".to_string(),
@@ -62,8 +52,6 @@ error[E0308]: mismatched types
 error[E0308]: mismatched types
   --> $DIR/abridged.rs:52:5
    |
-51 |   fn e() -> X<X<String, String>, String> {
-   |             ---------------------------- expected because of this return type
 52 | /     X {
 53 | |         x: X {
 54 | |             x: "".to_string(),
diff --git a/src/test/ui/mismatched_types/issue-19109.stderr b/src/test/ui/mismatched_types/issue-19109.stderr
@@ -2,10 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-19109.rs:14:5
    |
 13 | fn function(t: &mut Trait) {
-   |                            -
-   |                            |
-   |                            help: possibly return type missing here? `-> *mut Trait `
-   |                            expected `()` because of this default return type
+   |                            - help: possibly return type missing here? `-> *mut Trait `
 14 |     t as *mut Trait
    |     ^^^^^^^^^^^^^^^ expected (), found *-ptr
    |
diff --git a/src/test/ui/resolve/token-error-correct-3.stderr b/src/test/ui/resolve/token-error-correct-3.stderr
@@ -34,9 +34,6 @@ error[E0425]: cannot find function `is_directory` in this scope
 error[E0308]: mismatched types
   --> $DIR/token-error-correct-3.rs:25:13
    |
-20 |                                                                -> io::Result<bool> {
-   |                                                                   ---------------- expected `()` because of this return type
-...
 25 |             fs::create_dir_all(path.as_ref()).map(|()| true) //~ ERROR: mismatched types
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^- help: did you mean to add a semicolon here? `;`
    |             |

Original file line number	Diff line number	Diff line change
`@@ -1174,12 +1174,6 @@ impl<'gcx, 'tcx, 'exprs, E> CoerceMany<'gcx, 'tcx, 'exprs, E>`
`1174`	`1174`	`expected, found,`
`1175`	`1175`	`cause.span, blk_id);`
`1176`	`1176`	`}`
`1177`		`- ObligationCauseCode::ReturnType(ret_id) => {`
`1178`		`- db = fcx.report_mismatched_types(cause, expected, found, err);`
`1179`		`- if let Some((fn_decl, _)) = fcx.get_fn_decl(ret_id) {`
`1180`		`- fcx.point_to_type_requirement(&mut db, &fn_decl, expected);`
`1181`		`- }`
`1182`		`- }`
`1183`	`1177`	`_ => {`
`1184`	`1178`	`db = fcx.report_mismatched_types(cause, expected, found, err);`
`1185`	`1179`	`}`
Original file line number	Diff line number	Diff line change
`@@ -1,8 +1,6 @@`
`1`	`1`	`error[E0308]: mismatched types`
`2`	`2`	`--> $DIR/issue-13624.rs:17:5`
`3`	`3`	`\|`
`4`		`-16 \| pub fn get_enum_struct_variant() -> () {`
`5`		- \| -- expected `()` because of this return type
`6`	`4`	`17 \| Enum::EnumStructVariant { x: 1, y: 2, z: 3 }`
`7`	`5`	\| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found enum `a::Enum`
`8`	`6`	`\|`
Original file line number	Diff line number	Diff line change
`@@ -2,10 +2,7 @@ error[E0308]: mismatched types`
`2`	`2`	`--> $DIR/issue-20862.rs:12:5`
`3`	`3`	`\|`
`4`	`4`	`11 \| fn foo(x: i32) {`
`5`		`- \| -`
`6`		`- \| \|`
`7`		`- \| possibly return type missing here?`
`8`		- \| expected `()` because of this default return type
	`5`	`+ \| - possibly return type missing here?`
`9`	`6`	`12 \| \|y\| x + y`
`10`	`7`	`\| ^^^^^^^^^ expected (), found closure`
`11`	`8`	`\|`
Original file line number	Diff line number	Diff line change
@@ -11,9 +11,6 @@ error[E0277]: the trait bound `{integer}: Scalar` is not satisfied
`11`	`11`	`error[E0308]: mismatched types`
`12`	`12`	`--> $DIR/issue-22645.rs:25:3`
`13`	`13`	`\|`
`14`		`-23 \| fn main() {`
`15`		- \| - expected `()` because of this default return type
`16`		`-24 \| let b = Bob + 3.5;`
`17`	`14`	`25 \| b + 3 //~ ERROR E0277`
`18`	`15`	\| ^^^^^ expected (), found struct `Bob`
`19`	`16`	`\|`
Original file line number	Diff line number	Diff line change
`@@ -8,10 +8,7 @@ error[E0308]: mismatched types`
`8`	`8`	`--> $DIR/issue-3563.rs:13:9`
`9`	`9`	`\|`
`10`	`10`	`12 \| fn a(&self) {`
`11`		`- \| -`
`12`		`- \| \|`
`13`		`- \| possibly return type missing here?`
`14`		- \| expected `()` because of this default return type
	`11`	`+ \| - possibly return type missing here?`
`15`	`12`	`13 \| \|\| self.b()`
`16`	`13`	`\| ^^^^^^^^^^^ expected (), found closure`
`17`	`14`	`\|`
Original file line number	Diff line number	Diff line change
`@@ -1,8 +1,6 @@`
`1`	`1`	`error[E0308]: mismatched types`
`2`	`2`	`--> $DIR/issue-5500.rs:12:5`
`3`	`3`	`\|`
`4`		`-11 \| fn main() {`
`5`		- \| - expected `()` because of this default return type
`6`	`4`	`12 \| &panic!()`
`7`	`5`	`\| ^^^^^^^^^ expected (), found reference`
`8`	`6`	`\|`
Original file line number	Diff line number	Diff line change
`@@ -1,8 +1,6 @@`
`1`	`1`	`error[E0308]: mismatched types`
`2`	`2`	`--> $DIR/unexpected-return-on-unit.rs:19:5`
`3`	`3`	`\|`
`4`		`-18 \| fn bar() {`
`5`		- \| - expected `()` because of this default return type
`6`	`4`	`19 \| foo()`
`7`	`5`	`\| ^^^^^ expected (), found usize`
`8`	`6`	`\|`
Original file line number	Diff line number	Diff line change
`@@ -1,9 +1,6 @@`
`1`	`1`	`error[E0308]: mismatched types`
`2`	`2`	`--> $DIR/equality.rs:25:5`
`3`	`3`	`\|`
`4`		`-21 \| fn two(x: bool) -> impl Foo {`
`5`		- \| -------- expected `i32` because of this return type
`6`		`-...`
`7`	`4`	`25 \| 0_u32`
`8`	`5`	`\| ^^^^^ expected i32, found u32`
`9`	`6`	`\|`
Original file line number	Diff line number	Diff line change
`@@ -1,8 +1,6 @@`
`1`	`1`	`error[E0308]: mismatched types`
`2`	`2`	`--> $DIR/abridged.rs:26:5`
`3`	`3`	`\|`
`4`		`-25 \| fn a() -> Foo {`
`5`		- \| --- expected `Foo` because of this return type
`6`	`4`	`26 \| Some(Foo { bar: 1 })`
`7`	`5`	\| ^^^^^^^^^^^^^^^^^^^^ expected struct `Foo`, found enum `std::option::Option`
`8`	`6`	`\|`
`@@ -12,8 +10,6 @@ error[E0308]: mismatched types`
`12`	`10`	`error[E0308]: mismatched types`
`13`	`11`	`--> $DIR/abridged.rs:30:5`
`14`	`12`	`\|`
`15`		`-29 \| fn a2() -> Foo {`
`16`		- \| --- expected `Foo` because of this return type
`17`	`13`	`30 \| Ok(Foo { bar: 1})`
`18`	`14`	\| ^^^^^^^^^^^^^^^^^ expected struct `Foo`, found enum `std::result::Result`
`19`	`15`	`\|`
`@@ -23,8 +19,6 @@ error[E0308]: mismatched types`
`23`	`19`	`error[E0308]: mismatched types`
`24`	`20`	`--> $DIR/abridged.rs:34:5`
`25`	`21`	`\|`
`26`		`-33 \| fn b() -> Option<Foo> {`
`27`		`- \| ----------- expected because of this return type`
`28`	`22`	`34 \| Foo { bar: 1 }`
`29`	`23`	\| ^^^^^^^^^^^^^^ expected enum `std::option::Option`, found struct `Foo`
`30`	`24`	`\|`
`@@ -34,8 +28,6 @@ error[E0308]: mismatched types`
`34`	`28`	`error[E0308]: mismatched types`
`35`	`29`	`--> $DIR/abridged.rs:38:5`
`36`	`30`	`\|`
`37`		`-37 \| fn c() -> Result<Foo, Bar> {`
`38`		`- \| ---------------- expected because of this return type`
`39`	`31`	`38 \| Foo { bar: 1 }`
`40`	`32`	\| ^^^^^^^^^^^^^^ expected enum `std::result::Result`, found struct `Foo`
`41`	`33`	`\|`
`@@ -45,8 +37,6 @@ error[E0308]: mismatched types`
`45`	`37`	`error[E0308]: mismatched types`
`46`	`38`	`--> $DIR/abridged.rs:42:5`
`47`	`39`	`\|`
`48`		`-41 \| fn d() -> X<X<String, String>, String> {`
`49`		`- \| ---------------------------- expected because of this return type`
`50`	`40`	`42 \| / X {`
`51`	`41`	`43 \| \| x: X {`
`52`	`42`	`44 \| \| x: "".to_string(),`
`@@ -62,8 +52,6 @@ error[E0308]: mismatched types`
`62`	`52`	`error[E0308]: mismatched types`
`63`	`53`	`--> $DIR/abridged.rs:52:5`
`64`	`54`	`\|`
`65`		`-51 \| fn e() -> X<X<String, String>, String> {`
`66`		`- \| ---------------------------- expected because of this return type`
`67`	`55`	`52 \| / X {`
`68`	`56`	`53 \| \| x: X {`
`69`	`57`	`54 \| \| x: "".to_string(),`
Original file line number	Diff line number	Diff line change
`@@ -2,10 +2,7 @@ error[E0308]: mismatched types`
`2`	`2`	`--> $DIR/issue-19109.rs:14:5`
`3`	`3`	`\|`
`4`	`4`	`13 \| fn function(t: &mut Trait) {`
`5`		`- \| -`
`6`		`- \| \|`
`7`		- \| help: possibly return type missing here? `-> *mut Trait `
`8`		- \| expected `()` because of this default return type
	`5`	+ \| - help: possibly return type missing here? `-> *mut Trait `
`9`	`6`	`14 \| t as *mut Trait`
`10`	`7`	`\| ^^^^^^^^^^^^^^^ expected (), found *-ptr`
`11`	`8`	`\|`