Suggest return type

6 files changed, 40 insertions, 7 deletions

diff --git a/src/test/ui/associated-types/defaults-specialization.stderr b/src/test/ui/associated-types/defaults-specialization.stderr
index 920f8322813..3c7dc1fc3c9 100644
--- a/src/test/ui/associated-types/defaults-specialization.stderr
+++ b/src/test/ui/associated-types/defaults-specialization.stderr
@@ -15,7 +15,10 @@ LL |     fn make() -> Self::Ty {
    |                  -------- type in trait
 ...
 LL |     fn make() -> u8 { 0 }
-   |                  ^^ expected associated type, found `u8`
+   |                  ^^
+   |                  |
+   |                  expected associated type, found `u8`
+   |                  help: change the output type to match the trait: `<A<T> as Tr>::Ty`
    |
    = note: expected fn pointer `fn() -> <A<T> as Tr>::Ty`
               found fn pointer `fn() -> u8`
@@ -30,7 +33,10 @@ LL |     default type Ty = bool;
    |     ----------------------- expected this associated type
 LL | 
 LL |     fn make() -> bool { true }
-   |                  ^^^^ expected associated type, found `bool`
+   |                  ^^^^
+   |                  |
+   |                  expected associated type, found `bool`
+   |                  help: change the output type to match the trait: `<B<T> as Tr>::Ty`
    |
    = note: expected fn pointer `fn() -> <B<T> as Tr>::Ty`
               found fn pointer `fn() -> bool`
diff --git a/src/test/ui/compare-method/bad-self-type.rs b/src/test/ui/compare-method/bad-self-type.rs
index 9eb978664bf..f42a9e49abd 100644
--- a/src/test/ui/compare-method/bad-self-type.rs
+++ b/src/test/ui/compare-method/bad-self-type.rs
@@ -15,9 +15,12 @@ impl Future for MyFuture {
 
 trait T {
     fn foo(self);
+    fn bar(self) -> Option<()>;
 }
 
 impl T for MyFuture {
     fn foo(self: Box<Self>) {}
     //~^ ERROR method `foo` has an incompatible type for trait
+    fn bar(self) {}
+    //~^ ERROR method `bar` has an incompatible type for trait
 }
diff --git a/src/test/ui/compare-method/bad-self-type.stderr b/src/test/ui/compare-method/bad-self-type.stderr
index 4d85ff86df5..74e7c562aa7 100644
--- a/src/test/ui/compare-method/bad-self-type.stderr
+++ b/src/test/ui/compare-method/bad-self-type.stderr
@@ -11,7 +11,7 @@ LL |     fn poll(self, _: &mut Context<'_>) -> Poll<()> {
               found fn pointer `fn(MyFuture, &mut Context<'_>) -> Poll<_>`
 
 error[E0053]: method `foo` has an incompatible type for trait
-  --> $DIR/bad-self-type.rs:21:18
+  --> $DIR/bad-self-type.rs:22:18
    |
 LL |     fn foo(self);
    |            ---- type in trait
@@ -25,6 +25,21 @@ LL |     fn foo(self: Box<Self>) {}
    = note: expected fn pointer `fn(MyFuture)`
               found fn pointer `fn(Box<MyFuture>)`
 
-error: aborting due to 2 previous errors
+error[E0053]: method `bar` has an incompatible type for trait
+  --> $DIR/bad-self-type.rs:24:18
+   |
+LL |     fn bar(self) -> Option<()>;
+   |                     ---------- type in trait
+...
+LL |     fn bar(self) {}
+   |                  ^
+   |                  |
+   |                  expected enum `Option`, found `()`
+   |                  help: change the output type to match the trait: `-> Option<()>`
+   |
+   = note: expected fn pointer `fn(MyFuture) -> Option<()>`
+              found fn pointer `fn(MyFuture)`
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0053`.
diff --git a/src/test/ui/issues/issue-21332.stderr b/src/test/ui/issues/issue-21332.stderr
index fd132687d71..d92966da17c 100644
--- a/src/test/ui/issues/issue-21332.stderr
+++ b/src/test/ui/issues/issue-21332.stderr
@@ -2,7 +2,10 @@ error[E0053]: method `next` has an incompatible type for trait
   --> $DIR/issue-21332.rs:5:27
    |
 LL |     fn next(&mut self) -> Result<i32, i32> { Ok(7) }
-   |                           ^^^^^^^^^^^^^^^^ expected enum `Option`, found enum `Result`
+   |                           ^^^^^^^^^^^^^^^^
+   |                           |
+   |                           expected enum `Option`, found enum `Result`
+   |                           help: change the output type to match the trait: `Option<i32>`
    |
    = note: expected fn pointer `fn(&mut S) -> Option<i32>`
               found fn pointer `fn(&mut S) -> Result<i32, i32>`
diff --git a/src/test/ui/issues/issue-35869.stderr b/src/test/ui/issues/issue-35869.stderr
index c104aa30cb0..71b2a9df095 100644
--- a/src/test/ui/issues/issue-35869.stderr
+++ b/src/test/ui/issues/issue-35869.stderr
@@ -50,7 +50,10 @@ LL |     fn qux() -> u8;
    |                 -- type in trait
 ...
 LL |     fn qux() -> u16 { 5u16 }
-   |                 ^^^ expected `u8`, found `u16`
+   |                 ^^^
+   |                 |
+   |                 expected `u8`, found `u16`
+   |                 help: change the output type to match the trait: `u8`
    |
    = note: expected fn pointer `fn() -> u8`
               found fn pointer `fn() -> u16`
diff --git a/src/test/ui/wrong-mul-method-signature.stderr b/src/test/ui/wrong-mul-method-signature.stderr
index 9be07cb1a74..9f8896f01ee 100644
--- a/src/test/ui/wrong-mul-method-signature.stderr
+++ b/src/test/ui/wrong-mul-method-signature.stderr
@@ -26,7 +26,10 @@ error[E0053]: method `mul` has an incompatible type for trait
   --> $DIR/wrong-mul-method-signature.rs:52:29
    |
 LL |     fn mul(self, s: f64) -> f64 {
-   |                             ^^^ expected `i32`, found `f64`
+   |                             ^^^
+   |                             |
+   |                             expected `i32`, found `f64`
+   |                             help: change the output type to match the trait: `i32`
    |
    = note: expected fn pointer `fn(Vec3, _) -> i32`
               found fn pointer `fn(Vec3, _) -> f64`