fix error on wrong path

crates/ra_hir/src/marks.rs

@@ -1,4 +1,5 @@
 test_utils::marks!(
+    bogus_paths
     name_res_works_for_broken_modules
     can_import_enum_variant
     type_var_cycles_resolve_completely

crates/ra_hir/src/nameres/collector.rs

@@ -213,18 +213,22 @@ where
                 }
             }
         } else {
-            let last_segment = import.path.segments.last().unwrap();
-            let name = import.alias.clone().unwrap_or_else(|| last_segment.name.clone());
-            log::debug!("resolved import {:?} ({:?}) to {:?}", name, import, def);
+            match import.path.segments.last() {
+                Some(last_segment) => {
+                    let name = import.alias.clone().unwrap_or_else(|| last_segment.name.clone());
+                    log::debug!("resolved import {:?} ({:?}) to {:?}", name, import, def);
 
-            // extern crates in the crate root are special-cased to insert entries into the extern prelude: rust-lang/rust#54658
-            if import.is_extern_crate && module_id == self.def_map.root {
-                if let Some(def) = def.take_types() {
-                    self.def_map.extern_prelude.insert(name.clone(), def);
+                    // extern crates in the crate root are special-cased to insert entries into the extern prelude: rust-lang/rust#54658
+                    if import.is_extern_crate && module_id == self.def_map.root {
+                        if let Some(def) = def.take_types() {
+                            self.def_map.extern_prelude.insert(name.clone(), def);
+                        }
+                    }
+                    let resolution = Resolution { def, import: Some(import_id) };
+                    self.update(module_id, Some(import_id), &[(name, resolution)]);
                 }
+                None => tested_by!(bogus_paths),
             }
-            let resolution = Resolution { def, import: Some(import_id) };
-            self.update(module_id, Some(import_id), &[(name, resolution)]);
         }
     }
 

crates/ra_hir/src/nameres/tests.rs

@@ -96,6 +96,32 @@ E: t
     )
 }
 
+#[test]
+fn bogus_paths() {
+    covers!(bogus_paths);
+    let map = def_map(
+        "
+        //- /lib.rs
+        mod foo;
+        struct S;
+        use self;
+
+        //- /foo/mod.rs
+        use super;
+        use crate;
+
+        ",
+    );
+    assert_snapshot_matches!(map, @r###"
+crate
+foo: t
+S: t v
+
+crate::foo
+"###
+    )
+}
+
 #[test]
 fn use_as() {
     let map = def_map(

crates/test_utils/src/marks.rs

@@ -30,13 +30,13 @@ use std::sync::atomic::{AtomicUsize, Ordering};
 
 #[macro_export]
 macro_rules! tested_by {
-    ($ident:ident) => {
+    ($ident:ident) => {{
         #[cfg(test)]
         {
             // sic! use call-site crate
             crate::marks::$ident.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
         }
-    };
+    }};
 }
 
 #[macro_export]