clean up alot, span_lint_and_sugg

clippy_lints/src/macro_use.rs

@@ -1,6 +1,7 @@
-use crate::utils::span_lint_and_help;
+use crate::utils::{snippet, span_lint_and_sugg};
 use if_chain::if_chain;
 use rustc_ast::ast;
+use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::edition::Edition;
@@ -35,24 +36,17 @@ impl EarlyLintPass for MacroUseImport {
                 .iter()
                 .find(|attr| attr.ident().map(|s| s.to_string()) == Some("macro_use".to_string()));
             then {
-                let msg = "`macro_use` attribute's are no longer needed in the Rust 2018 edition";
-                    let help = format!(
-                        "remove the attribute and import the macro directly `use {}::<macro name>`",
-                        use_tree
-                            .clone()
-                            .into_inner()
-                            .prefix
-                            .segments
-                            .iter()
-                            .enumerate()
-                            .map(|(i, s)| if i == 0 {
-                                s.ident.to_string()
-                            } else {
-                                format!("::{}", s.ident)
-                            })
-                            .collect::<String>(),
-                    );
-                span_lint_and_help(ecx, MACRO_USE_IMPORT, mac_attr.span, msg, &help);
+                let msg = "`macro_use` attributes are no longer needed in the Rust 2018 edition";
+                let help = format!("use {}::<macro name>", snippet(ecx, use_tree.span, "_"));
+                span_lint_and_sugg(
+                    ecx,
+                    MACRO_USE_IMPORT,
+                    mac_attr.span,
+                    msg,
+                    "remove the attribute and import the macro directly, try",
+                    help,
+                    Applicability::HasPlaceholders,
+                );
             }
         }
     }

tests/ui/macro_use_import.stderr

@@ -1,11 +1,10 @@
-error: `macro_use` attribute's are no longer needed in the Rust 2018 edition
+error: `macro_use` attributes are no longer needed in the Rust 2018 edition
   --> $DIR/macro_use_import.rs:5:1
    |
 LL | #[macro_use]
-   | ^^^^^^^^^^^^
+   | ^^^^^^^^^^^^ help: remove the attribute and import the macro directly, try: `use std::prelude::<macro name>`
    |
    = note: `-D clippy::macro-use-import` implied by `-D warnings`
-   = help: remove the attribute and import the macro directly `use std::prelude::<macro name>`
 
 error: aborting due to previous error