Improve lint message

Author: hkmatsumoto

clippy_lints/src/unnecessary_wrap.rs

@@ -100,7 +100,7 @@ impl<'tcx> LateLintPass<'tcx> for UnnecessaryWrap {
                 cx,
                 UNNECESSARY_WRAP,
                 span,
-                format!("this function's return value is unnecessarily wrapped by `{}`, return_type)",
+                format!("this function's return value is unnecessarily wrapped by `{}`", return_type).as_str(),
                 |diag| {
                     let inner_ty = return_ty(cx, hir_id)
                         .walk()

tests/ui/unnecessary_wrap.stderr

@@ -1,4 +1,4 @@
-error: this function returns unnecessarily wrapping data
+error: this function's return value is unnecessarily wrapped by `Option`
   --> $DIR/unnecessary_wrap.rs:8:1
    |
 LL | / fn func1(a: bool, b: bool) -> Option<i32> {
@@ -25,7 +25,7 @@ LL |         2
 LL |     } else {
  ...
 
-error: this function returns unnecessarily wrapping data
+error: this function's return value is unnecessarily wrapped by `Option`
   --> $DIR/unnecessary_wrap.rs:21:1
    |
 LL | / fn func2(a: bool, b: bool) -> Option<i32> {
@@ -51,7 +51,7 @@ LL |     } else {
 LL |         30
    |
 
-error: this function returns unnecessarily wrapping data
+error: this function's return value is unnecessarily wrapped by `Option`
   --> $DIR/unnecessary_wrap.rs:51:1
    |
 LL | / fn func5() -> Option<i32> {
@@ -68,7 +68,7 @@ help: ...and change the returning expressions
 LL |     1
    |
 
-error: this function returns unnecessarily wrapping data
+error: this function's return value is unnecessarily wrapped by `Result`
   --> $DIR/unnecessary_wrap.rs:61:1
    |
 LL | / fn func7() -> Result<i32, ()> {