From 0c14ea8ed79ebf0b7368659282136e876f247cc9 Mon Sep 17 00:00:00 2001
From: Glenn Hope <glenn.alexander.hope@gmail.com>
Date: Sun, 3 May 2020 10:56:25 -0700
Subject: [PATCH] Allow 'use super::*;' imports

---
 clippy_lints/src/wildcard_imports.rs | 19 +++++++++++---
 tests/ui/wildcard_imports.fixed      | 38 ++++++++++++++++++++++++++++
 tests/ui/wildcard_imports.rs         | 38 ++++++++++++++++++++++++++++
 tests/ui/wildcard_imports.stderr     | 20 ++++++++++++++-
 4 files changed, 111 insertions(+), 4 deletions(-)

diff --git a/clippy_lints/src/wildcard_imports.rs b/clippy_lints/src/wildcard_imports.rs
index f3038861cee..70ad9a60a02 100644
--- a/clippy_lints/src/wildcard_imports.rs
+++ b/clippy_lints/src/wildcard_imports.rs
@@ -3,7 +3,7 @@ use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{
     def::{DefKind, Res},
-    Item, ItemKind, UseKind,
+    Item, ItemKind, PathSegment, UseKind,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -83,8 +83,8 @@ impl LateLintPass<'_, '_> for WildcardImports {
         if_chain! {
             if !in_macro(item.span);
             if let ItemKind::Use(use_path, UseKind::Glob) = &item.kind;
-            // don't lint prelude glob imports
-            if !use_path.segments.iter().last().map_or(false, |ps| ps.ident.as_str() == "prelude");
+            if !is_prelude_import(use_path.segments);
+            if !is_super_only_import_in_test(use_path.segments);
             let used_imports = cx.tcx.names_imported_by_glob_use(item.hir_id.owner);
             if !used_imports.is_empty(); // Already handled by `unused_imports`
             then {
@@ -154,3 +154,16 @@ impl LateLintPass<'_, '_> for WildcardImports {
         }
     }
 }
+
+// Allow "...prelude::*" imports.
+// Many crates have a prelude, and it is imported as a glob by design.
+fn is_prelude_import(segments: &[PathSegment<'_>]) -> bool {
+    segments.iter().last().map_or(false, |ps| ps.ident.as_str() == "prelude")
+}
+
+// Allow "super::*" imports.
+// This is intended primarily to ease the process of writing unit tests.
+fn is_super_only_import_in_test(segments: &[PathSegment<'_>]) -> bool {
+    segments.iter().len() == 1 &&
+        segments.first().map_or(false, |ps| ps.ident.as_str() == "super")
+}
diff --git a/tests/ui/wildcard_imports.fixed b/tests/ui/wildcard_imports.fixed
index ed6cc00ef04..003f11009a0 100644
--- a/tests/ui/wildcard_imports.fixed
+++ b/tests/ui/wildcard_imports.fixed
@@ -155,3 +155,41 @@ fn test_weird_formatting() {
     exported();
     foo();
 }
+
+mod test_super_imports {
+    fn foofoo() {}
+
+    mod use_super {
+        use super::*;
+
+        fn with_super() {
+            let _ = foofoo();
+        }
+    }
+
+    mod use_explicit {
+        use test_super_imports::foofoo;
+
+        fn with_explicit() {
+            let _ = foofoo();
+        }
+    }
+
+    mod use_double_super {
+        mod inner {
+            use super::super::foofoo;
+
+            fn with_double_super() {
+                let _ = foofoo();
+            }
+        }
+    }
+
+    mod use_super_explicit {
+        use super::super::test_super_imports::foofoo;
+
+        fn with_super_explicit() {
+            let _ = foofoo();
+        }
+    }
+}
diff --git a/tests/ui/wildcard_imports.rs b/tests/ui/wildcard_imports.rs
index c6d6efaece8..7bd57c7965a 100644
--- a/tests/ui/wildcard_imports.rs
+++ b/tests/ui/wildcard_imports.rs
@@ -156,3 +156,41 @@ fn test_weird_formatting() {
     exported();
     foo();
 }
+
+mod test_super_imports {
+    fn foofoo() {}
+
+    mod use_super {
+        use super::*;
+
+        fn with_super() {
+            let _ = foofoo();
+        }
+    }
+
+    mod use_explicit {
+        use test_super_imports::*;
+
+        fn with_explicit() {
+            let _ = foofoo();
+        }
+    }
+
+    mod use_double_super {
+        mod inner {
+            use super::super::*;
+
+            fn with_double_super() {
+                let _ = foofoo();
+            }
+        }
+    }
+
+    mod use_super_explicit {
+        use super::super::test_super_imports::*;
+
+        fn with_super_explicit() {
+            let _ = foofoo();
+        }
+    }
+}
diff --git a/tests/ui/wildcard_imports.stderr b/tests/ui/wildcard_imports.stderr
index 050e4c6304f..858dc28797f 100644
--- a/tests/ui/wildcard_imports.stderr
+++ b/tests/ui/wildcard_imports.stderr
@@ -92,5 +92,23 @@ LL |       use crate:: fn_mod::
 LL | |         *;
    | |_________^ help: try: `crate:: fn_mod::foo`
 
-error: aborting due to 15 previous errors
+error: usage of wildcard import
+  --> $DIR/wildcard_imports.rs:172:13
+   |
+LL |         use test_super_imports::*;
+   |             ^^^^^^^^^^^^^^^^^^^^^ help: try: `test_super_imports::foofoo`
+
+error: usage of wildcard import
+  --> $DIR/wildcard_imports.rs:181:17
+   |
+LL |             use super::super::*;
+   |                 ^^^^^^^^^^^^^^^ help: try: `super::super::foofoo`
+
+error: usage of wildcard import
+  --> $DIR/wildcard_imports.rs:190:13
+   |
+LL |         use super::super::test_super_imports::*;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `super::super::test_super_imports::foofoo`
+
+error: aborting due to 18 previous errors