warn on useing all variants of an enum

src/enum_glob_use.rs

@@ -0,0 +1,61 @@
+//! lint on `use`ing all variants of an enum
+
+use rustc::lint::{LateLintPass, LintPass, LateContext, LintArray, LintContext};
+use rustc_front::hir::*;
+use rustc::front::map::Node::NodeItem;
+use rustc::front::map::PathElem::PathName;
+use rustc::middle::ty::TyEnum;
+use utils::span_lint;
+use syntax::codemap::Span;
+use syntax::ast::NodeId;
+
+/// **What it does:** Warns when `use`ing all variants of an enum
+///
+/// **Why is this bad?** It is usually better style to use the prefixed name of an enum variant, rather than importing variants
+///
+/// **Known problems:** Old-style enums that prefix the variants are still around
+///
+/// **Example:** `use std::cmp::Ordering::*;`
+declare_lint! { pub ENUM_GLOB_USE, Allow,
+    "finds use items that import all variants of an enum" }
+
+pub struct EnumGlobUse;
+
+impl LintPass for EnumGlobUse {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(ENUM_GLOB_USE)
+    }
+}
+
+impl LateLintPass for EnumGlobUse {
+    fn check_mod(&mut self, cx: &LateContext, m: &Mod, _: Span, _: NodeId) {
+        // only check top level `use` statements
+        for item in &m.item_ids {
+            self.lint_item(cx, cx.krate.item(item.id));
+        }
+    }
+}
+
+impl EnumGlobUse {
+    fn lint_item(&self, cx: &LateContext, item: &Item) {
+        if item.vis == Visibility::Public {
+            return; // re-exports are fine
+        }
+        if let ItemUse(ref item_use) = item.node {
+            if let ViewPath_::ViewPathGlob(_) = item_use.node {
+                let def = cx.tcx.def_map.borrow()[&item.id];
+                if let Some(NodeItem(it)) = cx.tcx.map.get_if_local(def.def_id()) {
+                    if let ItemEnum(..) = it.node {
+                        span_lint(cx, ENUM_GLOB_USE, item.span, "don't use glob imports for enum variants");
+                    }
+                } else {
+                    if let Some(&PathName(_)) = cx.sess().cstore.item_path(def.def_id()).last() {
+                        if let TyEnum(..) = cx.sess().cstore.item_type(&cx.tcx, def.def_id()).ty.sty {
+                            span_lint(cx, ENUM_GLOB_USE, item.span, "don't use glob imports for enum variants");
+                        }
+                    }
+                }
+            }
+        }
+    }
+}

src/lib.rs

@@ -37,6 +37,7 @@ pub mod utils;
 pub mod consts;
 pub mod types;
 pub mod misc;
+pub mod enum_glob_use;
 pub mod eq_op;
 pub mod bit_mask;
 pub mod ptr_arg;
@@ -95,6 +96,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_late_lint_pass(box misc::CmpNan);
     reg.register_late_lint_pass(box eq_op::EqOp);
     reg.register_early_lint_pass(box enum_variants::EnumVariantNames);
+    reg.register_late_lint_pass(box enum_glob_use::EnumGlobUse);
     reg.register_late_lint_pass(box bit_mask::BitMask);
     reg.register_late_lint_pass(box ptr_arg::PtrArg);
     reg.register_late_lint_pass(box needless_bool::NeedlessBool);
@@ -153,6 +155,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
 
 
     reg.register_lint_group("clippy_pedantic", vec![
+        enum_glob_use::ENUM_GLOB_USE,
         matches::SINGLE_MATCH_ELSE,
         methods::OPTION_UNWRAP_USED,
         methods::RESULT_UNWRAP_USED,