Use suggestion for redundant_closure

src/eta_reduction.rs

@@ -2,7 +2,7 @@ use rustc::lint::*;
 use rustc_front::hir::*;
 use rustc::middle::ty;
 
-use utils::{snippet, span_lint, is_adjusted};
+use utils::{snippet_opt, span_lint_and_then, is_adjusted};
 
 
 #[allow(missing_copy_implementations)]
@@ -75,9 +75,15 @@ fn check_closure(cx: &LateContext, expr: &Expr) {
                         return
                     }
                 }
-                span_lint(cx, REDUNDANT_CLOSURE, expr.span, &format!(
-                    "redundant closure found. Consider using `{}` in its place",
-                    snippet(cx, caller.span, "..")));
+                span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span,
+                                   "redundant closure found",
+                                   || {
+                    if let Some(snippet) = snippet_opt(cx, caller.span) {
+                        cx.sess().span_suggestion(expr.span,
+                                                  "remove closure as shown:",
+                                                  snippet);
+                    }
+                });
             }
         }
     }

src/utils.rs

@@ -195,6 +195,11 @@ pub fn snippet<'a, T: LintContext>(cx: &T, span: Span, default: &'a str) -> Cow<
     cx.sess().codemap().span_to_snippet(span).map(From::from).unwrap_or(Cow::Borrowed(default))
 }
 
+/// Converts a span to a code snippet. Returns None if not available.
+pub fn snippet_opt<T: LintContext>(cx: &T, span: Span) -> Option<String> {
+    cx.sess().codemap().span_to_snippet(span).ok()
+}
+
 /// convert a span (from a block) to a code snippet if available, otherwise use default, e.g.
 /// `snippet(cx, expr.span, "..")`
 /// This trims the code of indentation, except for the first line
@@ -320,6 +325,17 @@ pub fn span_note_and_lint<T: LintContext>(cx: &T, lint: &'static Lint, span: Spa
     }
 }
 
+pub fn span_lint_and_then<T: LintContext, F>(cx: &T, lint: &'static Lint, sp: Span,
+        msg: &str, f: F) where F: Fn() {
+    cx.span_lint(lint, sp, msg);
+    if cx.current_level(lint) != Level::Allow {
+        f();
+        cx.sess().fileline_help(sp, &format!("for further information visit \
+            https://github.com/Manishearth/rust-clippy/wiki#{}",
+            lint.name_lower()))
+    }
+}
+
 /// return the base type for references and raw pointers
 pub fn walk_ptrs_ty(ty: ty::Ty) -> ty::Ty {
     match ty.sty {

tests/compile-fail/eta.rs

@@ -5,11 +5,17 @@
 
 fn main() {
     let a = Some(1u8).map(|a| foo(a));
-    //~^ ERROR redundant closure found. Consider using `foo` in its place
+    //~^ ERROR redundant closure found
+    //~| HELP remove closure as shown
+    //~| SUGGESTION let a = Some(1u8).map(foo);
     meta(|a| foo(a));
-    //~^ ERROR redundant closure found. Consider using `foo` in its place
+    //~^ ERROR redundant closure found
+    //~| HELP remove closure as shown
+    //~| SUGGESTION meta(foo);
     let c = Some(1u8).map(|a| {1+2; foo}(a));
-    //~^ ERROR redundant closure found. Consider using `{1+2; foo}` in its place
+    //~^ ERROR redundant closure found
+    //~| HELP remove closure as shown
+    //~| SUGGESTION let c = Some(1u8).map({1+2; foo});
     let d = Some(1u8).map(|a| foo((|b| foo2(b))(a))); //is adjusted?
     all(&[1, 2, 3], &&2, |x, y| below(x, y)); //is adjusted
     unsafe {