code suggestion for deprecated-attribute lint

Also, fix the deprecation message for the late no-debug feature.

Author: zackmdavis

src/librustc_lint/builtin.rs

@@ -650,10 +650,11 @@ impl EarlyLintPass for DeprecatedAttr {
                                              ref name,
                                              ref reason,
                                              _) = g {
-                    cx.span_lint(DEPRECATED,
-                                 attr.span,
-                                 &format!("use of deprecated attribute `{}`: {}. See {}",
-                                          name, reason, link));
+                    let msg = format!("use of deprecated attribute `{}`: {}. See {}",
+                                      name, reason, link);
+                    let mut err = cx.struct_span_lint(DEPRECATED, attr.span, &msg);
+                    err.span_suggestion_short(attr.span, "remove this attribute", "".to_owned());
+                    err.emit();
                 }
                 return;
             }

src/libsyntax/feature_gate.rs

@@ -824,7 +824,8 @@ pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeG
     ("no_debug", Whitelisted, Gated(
         Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721"),
         "no_debug",
-        "the `#[no_debug]` attribute is an experimental feature",
+        "the `#[no_debug]` attribute was an experimental feature that has been \
+         deprecated due to lack of demand",
         cfg_fn!(no_debug))),
     ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
                                                        "omit_gdb_pretty_printer_section",

src/test/compile-fail/feature-gate-no-debug.rs

@@ -10,5 +10,5 @@
 
 #![allow(deprecated)]
 
-#[no_debug] //~ ERROR the `#[no_debug]` attribute is
+#[no_debug] //~ ERROR the `#[no_debug]` attribute was
 fn main() {}