Suggest lint groups

compiler/rustc_lint/src/context.rs

@@ -468,17 +468,17 @@ impl LintStore {
 
     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
         let name_lower = lint_name.to_lowercase();
-        let symbols =
-            self.get_lints().iter().map(|l| Symbol::intern(&l.name_lower())).collect::<Vec<_>>();
 
         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
             // First check if the lint name is (partly) in upper case instead of lower case...
-            CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)))
-        } else {
-            // ...if not, search for lints with a similar name
-            let suggestion = find_best_match_for_name(&symbols, Symbol::intern(&name_lower), None);
-            CheckLintNameResult::NoLint(suggestion)
+            return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
         }
+        // ...if not, search for lints with a similar name
+        let groups = self.lint_groups.keys().copied().map(Symbol::intern);
+        let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
+        let names: Vec<Symbol> = groups.chain(lints).collect();
+        let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
+        CheckLintNameResult::NoLint(suggestion)
     }
 
     fn check_tool_name_for_backwards_compat(

src/test/rustdoc-ui/unknown-renamed-lints.stderr

@@ -14,7 +14,7 @@ error: unknown lint: `rustdoc::x`
   --> $DIR/unknown-renamed-lints.rs:7:9
    |
 LL | #![deny(rustdoc::x)]
-   |         ^^^^^^^^^^
+   |         ^^^^^^^^^^ help: did you mean: `rustdoc::all`
 
 error: lint `intra_doc_link_resolution_failure` has been renamed to `rustdoc::broken_intra_doc_links`
   --> $DIR/unknown-renamed-lints.rs:9:9

src/test/ui/lint/lint-unknown-lint.rs

@@ -6,4 +6,8 @@
                    //~| HELP did you mean
                    //~| SUGGESTION dead_code
 
+#![deny(rust_2018_idiots)] //~ ERROR unknown lint
+                           //~| HELP did you mean
+                           //~| SUGGESTION rust_2018_idioms
+
 fn main() {}

src/test/ui/lint/lint-unknown-lint.stderr

@@ -16,5 +16,11 @@ error: unknown lint: `dead_cod`
 LL | #![deny(dead_cod)]
    |         ^^^^^^^^ help: did you mean: `dead_code`
 
-error: aborting due to 2 previous errors
+error: unknown lint: `rust_2018_idiots`
+  --> $DIR/lint-unknown-lint.rs:9:9
+   |
+LL | #![deny(rust_2018_idiots)]
+   |         ^^^^^^^^^^^^^^^^ help: did you mean: `rust_2018_idioms`
+
+error: aborting due to 3 previous errors