Fix crash in use-self lint

Fixes #4727

Author: Michael Wright

clippy_lints/src/use_self.rs

@@ -223,7 +223,7 @@ struct UseSelfVisitor<'a, 'tcx> {
 
 impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
     fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
-        if path.segments.len() >= 2 {
+        if path.segments.len() >= 2 && !path.segments.iter().any(|p| p.ident.span.is_dummy()) {
             let last_but_one = &path.segments[path.segments.len() - 2];
             if last_but_one.ident.name != kw::SelfUpper {
                 let enum_def_id = match path.res {

tests/ui/crashes/ice-4727-aux.rs

@@ -0,0 +1,13 @@
+//ignore-test
+
+// This file is used by the ice-4727 test but isn't itself a test.
+//
+pub trait Trait {
+    fn fun(par: &str) -> &str;
+}
+
+impl Trait for str {
+    fn fun(par: &str) -> &str {
+        &par[0..1]
+    }
+}

tests/ui/crashes/ice-4727.rs

@@ -0,0 +1,8 @@
+// run-pass
+
+#![warn(clippy::use_self)]
+
+#[path = "ice-4727-aux.rs"]
+mod aux;
+
+fn main() {}

tests/ui/use_self.fixed

@@ -332,3 +332,17 @@ mod issue3567 {
         }
     }
 }
+
+// Test with paths in ranges
+mod paths_in_ranges {
+    struct S {}
+
+    impl S {
+        const A: usize = 0;
+        const B: usize = 1;
+
+        fn f<'a>(&self, p: &'a [u8]) -> &'a [u8] {
+            &p[Self::A..Self::B]
+        }
+    }
+}

tests/ui/use_self.rs

@@ -332,3 +332,17 @@ mod issue3567 {
         }
     }
 }
+
+// Test with paths in ranges
+mod paths_in_ranges {
+    struct S {}
+
+    impl S {
+        const A: usize = 0;
+        const B: usize = 1;
+
+        fn f<'a>(&self, p: &'a [u8]) -> &'a [u8] {
+            &p[S::A..S::B]
+        }
+    }
+}

tests/ui/use_self.stderr

@@ -222,5 +222,17 @@ error: unnecessary structure name repetition
 LL |             TestStruct::from_something()
    |             ^^^^^^^^^^ help: use the applicable keyword: `Self`
 
-error: aborting due to 36 previous errors
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:345:16
+   |
+LL |             &p[S::A..S::B]
+   |                ^ help: use the applicable keyword: `Self`
+
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:345:22
+   |
+LL |             &p[S::A..S::B]
+   |                      ^ help: use the applicable keyword: `Self`
+
+error: aborting due to 38 previous errors