Fix vec_box scope error

Fixes rust-lang#6236

Author: camsteffen

clippy_lints/src/types.rs

@@ -553,7 +553,7 @@ impl Types {
                                     hir_ty.span,
                                     "`Vec<T>` is already on the heap, the boxing is unnecessary.",
                                     "try",
-                                    format!("Vec<{}>", ty_ty),
+                                    format!("Vec<{}>", snippet(cx, boxed_ty.span, "..")),
                                     Applicability::MachineApplicable,
                                 );
                                 return; // don't recurse into the type

tests/ui/vec_box_sized.fixed

@@ -35,4 +35,18 @@ mod should_not_trigger {
     }
 }
 
+mod inner_mod {
+    mod inner {
+        pub struct S;
+    }
+
+    mod inner2 {
+        use super::inner::S;
+
+        pub fn f() -> Vec<S> {
+            vec![]
+        }
+    }
+}
+
 fn main() {}

tests/ui/vec_box_sized.rs

@@ -35,4 +35,18 @@ mod should_not_trigger {
     }
 }
 
+mod inner_mod {
+    mod inner {
+        pub struct S;
+    }
+
+    mod inner2 {
+        use super::inner::S;
+
+        pub fn f() -> Vec<Box<S>> {
+            vec![]
+        }
+    }
+}
+
 fn main() {}

tests/ui/vec_box_sized.stderr

@@ -18,5 +18,11 @@ error: `Vec<T>` is already on the heap, the boxing is unnecessary.
 LL |     struct B(Vec<Vec<Box<(u32)>>>);
    |                  ^^^^^^^^^^^^^^^ help: try: `Vec<u32>`
 
-error: aborting due to 3 previous errors
+error: `Vec<T>` is already on the heap, the boxing is unnecessary.
+  --> $DIR/vec_box_sized.rs:46:23
+   |
+LL |         pub fn f() -> Vec<Box<S>> {
+   |                       ^^^^^^^^^^^ help: try: `Vec<S>`
+
+error: aborting due to 4 previous errors