Add tests for turbofish suggestions

Author: estebank

src/test/ui/suggestions/appropriate-type-param-turbofish.rs

@@ -0,0 +1,45 @@
+mod a {
+    fn foo() {
+        vec![1, 2, 3].into_iter().collect(); //~ ERROR type annotations needed
+    }
+    fn bar() {
+        vec!["a", "b", "c"].into_iter().collect(); //~ ERROR type annotations needed
+    }
+    fn qux() {
+        vec!['a', 'b', 'c'].into_iter().collect(); //~ ERROR type annotations needed
+    }
+}
+mod b {
+    fn foo() {
+        let _ = vec![1, 2, 3].into_iter().collect(); //~ ERROR type annotations needed
+    }
+    fn bar() {
+        let _ = vec!["a", "b", "c"].into_iter().collect(); //~ ERROR type annotations needed
+    }
+    fn qux() {
+        let _ = vec!['a', 'b', 'c'].into_iter().collect(); //~ ERROR type annotations needed
+    }
+}
+
+trait T: Sized {
+    fn new() -> Self;
+}
+fn x<X: T>() -> X {
+    T::new()
+}
+struct S;
+impl T for S {
+    fn new() -> Self {
+        S
+    }
+}
+
+fn foo() {
+    x(); //~ ERROR type annotations needed
+}
+
+fn bar() {
+    let _ = x(); //~ ERROR type annotations needed
+}
+
+fn main() {}

src/test/ui/suggestions/appropriate-type-param-turbofish.stderr

@@ -0,0 +1,101 @@
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:3:35
+   |
+LL |         vec![1, 2, 3].into_iter().collect();
+   |                                   ^^^^^^^ cannot infer type for type parameter `B` declared on the associated function `collect`
+   |
+   = note: cannot satisfy `_: std::iter::FromIterator<i32>`
+help: consider specifying the type argument in the method call
+   |
+LL |         vec![1, 2, 3].into_iter().collect::<B>();
+   |                                          ^^^^^
+
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:6:41
+   |
+LL |         vec!["a", "b", "c"].into_iter().collect();
+   |                                         ^^^^^^^ cannot infer type for type parameter `B` declared on the associated function `collect`
+   |
+   = note: cannot satisfy `_: std::iter::FromIterator<&str>`
+help: consider specifying the type argument in the method call
+   |
+LL |         vec!["a", "b", "c"].into_iter().collect::<B>();
+   |                                                ^^^^^
+
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:9:41
+   |
+LL |         vec!['a', 'b', 'c'].into_iter().collect();
+   |                                         ^^^^^^^ cannot infer type for type parameter `B` declared on the associated function `collect`
+   |
+   = note: cannot satisfy `_: std::iter::FromIterator<char>`
+help: consider specifying the type argument in the method call
+   |
+LL |         vec!['a', 'b', 'c'].into_iter().collect::<B>();
+   |                                                ^^^^^
+
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:14:43
+   |
+LL |         let _ = vec![1, 2, 3].into_iter().collect();
+   |             -                             ^^^^^^^ cannot infer type for type parameter `B` declared on the associated function `collect`
+   |             |
+   |             consider giving this pattern a type
+   |
+   = note: cannot satisfy `_: std::iter::FromIterator<i32>`
+
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:17:49
+   |
+LL |         let _ = vec!["a", "b", "c"].into_iter().collect();
+   |             -                                   ^^^^^^^ cannot infer type for type parameter `B` declared on the associated function `collect`
+   |             |
+   |             consider giving this pattern a type
+   |
+   = note: cannot satisfy `_: std::iter::FromIterator<&str>`
+
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:20:49
+   |
+LL |         let _ = vec!['a', 'b', 'c'].into_iter().collect();
+   |             -                                   ^^^^^^^ cannot infer type for type parameter `B` declared on the associated function `collect`
+   |             |
+   |             consider giving this pattern a type
+   |
+   = note: cannot satisfy `_: std::iter::FromIterator<char>`
+
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:38:5
+   |
+LL | fn x<X: T>() -> X {
+   |         - required by this bound in `x`
+...
+LL |     x();
+   |     ^ cannot infer type for type parameter `X` declared on the function `x`
+   |
+   = note: cannot satisfy `_: T`
+help: consider specifying the type argument in the function call
+   |
+LL |     x::<X>();
+   |      ^^^^^
+
+error[E0283]: type annotations needed
+  --> $DIR/appropriate-type-param-turbofish.rs:42:13
+   |
+LL | fn x<X: T>() -> X {
+   |         - required by this bound in `x`
+...
+LL |     let _ = x();
+   |         -   ^ cannot infer type for type parameter `X` declared on the function `x`
+   |         |
+   |         consider giving this pattern a type
+   |
+   = note: cannot satisfy `_: T`
+help: consider specifying the type argument in the function call
+   |
+LL |     let _ = x::<X>();
+   |              ^^^^^
+
+error: aborting due to 8 previous errors
+
+For more information about this error, try `rustc --explain E0283`.