Add empty_enum lint (just a copy of large_enum_variant for now)

clippy_lints/src/derive.rs

@@ -173,6 +173,8 @@ fn check_copy_clone<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, item: &Item, trait_ref
                            EXPL_IMPL_CLONE_ON_COPY,
                            item.span,
                            "you are implementing `Clone` explicitly on a `Copy` type",
-                           |db| { db.span_note(item.span, "consider deriving `Clone` or removing `Copy`"); });
+                           |db| {
+            db.span_note(item.span, "consider deriving `Clone` or removing `Copy`");
+        });
     }
 }

clippy_lints/src/empty_enum.rs

@@ -0,0 +1,82 @@
+//! lint when there is an enum with no variants
+
+use rustc::lint::*;
+use rustc::hir::*;
+use utils::{span_lint_and_then, snippet_opt};
+use rustc::ty::layout::TargetDataLayout;
+use rustc::ty::TypeFoldable;
+use rustc::traits::Reveal;
+
+/// **What it does:** Checks for `enum`s with no variants.
+///
+/// **Why is this bad?** Enum's with no variants should be replaced with `!`.
+///
+/// **Known problems:** None.
+///
+/// **Example:**
+/// ```rust
+/// enum Test {}
+/// ```
+declare_lint! {
+    pub EMPTY_ENUM,
+    Warn,
+    "enum with no variants"
+}
+
+#[derive(Copy,Clone)]
+pub struct EmptyEnum;
+
+impl LintPass for EmptyEnum {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(EMPTY_ENUM)
+    }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EmptyEnum {
+    fn check_item(&mut self, cx: &LateContext, item: &Item) {
+        let did = cx.tcx.hir.local_def_id(item.id);
+        if let ItemEnum(ref def, _) = item.node {
+            let ty = cx.tcx.item_type(did);
+            let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
+            for (i, variant) in adt.variants.iter().enumerate() {
+                let data_layout = TargetDataLayout::parse(cx.sess());
+                cx.tcx.infer_ctxt((), Reveal::All).enter(|infcx| {
+                    let size: u64 = variant.fields
+                        .iter()
+                        .map(|f| {
+                            let ty = cx.tcx.item_type(f.did);
+                            if ty.needs_subst() {
+                                0 // we can't reason about generics, so we treat them as zero sized
+                            } else {
+                                ty.layout(&infcx)
+                                    .expect("layout should be computable for concrete type")
+                                    .size(&data_layout)
+                                    .bytes()
+                            }
+                        })
+                        .sum();
+                    if size > 0 {
+                        span_lint_and_then(cx, EMPTY_ENUM, def.variants[i].span, "large enum variant found", |db| {
+                            if variant.fields.len() == 1 {
+                                let span = match def.variants[i].node.data {
+                                    VariantData::Struct(ref fields, _) |
+                                    VariantData::Tuple(ref fields, _) => fields[0].ty.span,
+                                    VariantData::Unit(_) => unreachable!(),
+                                };
+                                if let Some(snip) = snippet_opt(cx, span) {
+                                    db.span_suggestion(span,
+                                                       "consider boxing the large fields to reduce the total size of \
+                                                        the enum",
+                                                       format!("Box<{}>", snip));
+                                    return;
+                                }
+                            }
+                            db.span_help(def.variants[i].span,
+                                         "consider boxing the large fields to reduce the total size of the enum");
+                        });
+                    }
+                });
+            }
+        }
+    }
+}

clippy_lints/src/lib.rs

@@ -72,6 +72,7 @@ pub mod derive;
 pub mod doc;
 pub mod double_parens;
 pub mod drop_forget_ref;
+pub mod empty_enum;
 pub mod entry;
 pub mod enum_clike;
 pub mod enum_glob_use;
@@ -265,6 +266,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
         max_single_char_names: conf.max_single_char_names,
     });
     reg.register_late_lint_pass(box drop_forget_ref::Pass);
+    reg.register_late_lint_pass(box empty_enum::EmptyEnum);
     reg.register_late_lint_pass(box types::AbsurdExtremeComparisons);
     reg.register_late_lint_pass(box types::InvalidUpcastComparisons);
     reg.register_late_lint_pass(box regex::Pass::default());

clippy_lints/src/map_clone.rs

@@ -1,8 +1,8 @@
 use rustc::lint::*;
 use rustc::hir::*;
 use syntax::ast;
-use utils::{is_adjusted, match_path, match_trait_method, match_type, remove_blocks, paths, snippet, span_help_and_lint,
-            walk_ptrs_ty, walk_ptrs_ty_depth, iter_input_pats};
+use utils::{is_adjusted, match_path, match_trait_method, match_type, remove_blocks, paths, snippet,
+            span_help_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, iter_input_pats};
 
 /// **What it does:** Checks for mapping `clone()` over an iterator.
 ///

clippy_lints/src/methods.rs

@@ -1213,7 +1213,9 @@ fn lint_single_char_pattern(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr)
                                SINGLE_CHAR_PATTERN,
                                arg.span,
                                "single-character string constant used as pattern",
-                               |db| { db.span_suggestion(expr.span, "try using a char instead:", hint); });
+                               |db| {
+                db.span_suggestion(expr.span, "try using a char instead:", hint);
+            });
         }
     }
 }

clippy_lints/src/needless_bool.rs

@@ -74,7 +74,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessBool {
                                    NEEDLESS_BOOL,
                                    e.span,
                                    "this if-then-else expression returns a bool literal",
-                                   |db| { db.span_suggestion(e.span, "you can reduce it to", hint); });
+                                   |db| {
+                    db.span_suggestion(e.span, "you can reduce it to", hint);
+                });
             };
             match (fetch_bool_block(then_block), fetch_bool_expr(else_expr)) {
                 (RetBool(true), RetBool(true)) |
@@ -121,7 +123,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoolComparison {
                                        BOOL_COMPARISON,
                                        e.span,
                                        "equality checks against true are unnecessary",
-                                       |db| { db.span_suggestion(e.span, "try simplifying it as shown:", hint); });
+                                       |db| {
+                        db.span_suggestion(e.span, "try simplifying it as shown:", hint);
+                    });
                 },
                 (Other, Bool(true)) => {
                     let hint = snippet(cx, left_side.span, "..").into_owned();
@@ -129,7 +133,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoolComparison {
                                        BOOL_COMPARISON,
                                        e.span,
                                        "equality checks against true are unnecessary",
-                                       |db| { db.span_suggestion(e.span, "try simplifying it as shown:", hint); });
+                                       |db| {
+                        db.span_suggestion(e.span, "try simplifying it as shown:", hint);
+                    });
                 },
                 (Bool(false), Other) => {
                     let hint = Sugg::hir(cx, right_side, "..");

clippy_lints/src/no_effect.rs

@@ -120,11 +120,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
                         return;
                     }
                 }
-                span_lint_and_then(cx,
-                                   UNNECESSARY_OPERATION,
-                                   stmt.span,
-                                   "statement can be reduced",
-                                   |db| { db.span_suggestion(stmt.span, "replace it with", snippet); });
+                span_lint_and_then(cx, UNNECESSARY_OPERATION, stmt.span, "statement can be reduced", |db| {
+                    db.span_suggestion(stmt.span, "replace it with", snippet);
+                });
             }
         }
     }

clippy_lints/src/precedence.rs

@@ -36,8 +36,7 @@ impl LintPass for Precedence {
 impl EarlyLintPass for Precedence {
     fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
         if let ExprKind::Binary(Spanned { node: op, .. }, ref left, ref right) = expr.node {
-            let span_sugg =
-                |expr: &Expr, sugg| {
+            let span_sugg = |expr: &Expr, sugg| {
                 span_lint_and_then(cx, PRECEDENCE, expr.span, "operator precedence can trip the unwary", |db| {
                     db.span_suggestion(expr.span, "consider parenthesizing your expression", sugg);
                 });

clippy_lints/src/shadow.rs

@@ -250,7 +250,9 @@ fn lint_shadow<'a, 'tcx: 'a>(
                                &format!("`{}` is shadowed by itself in `{}`",
                                         snippet(cx, pattern_span, "_"),
                                         snippet(cx, expr.span, "..")),
-                               |db| { db.span_note(prev_span, "previous binding is here"); });
+                               |db| {
+                db.span_note(prev_span, "previous binding is here");
+            });
         } else if contains_self(cx, name, expr) {
             span_lint_and_then(cx,
                                SHADOW_REUSE,
@@ -280,7 +282,9 @@ fn lint_shadow<'a, 'tcx: 'a>(
                            SHADOW_UNRELATED,
                            span,
                            &format!("`{}` shadows a previous declaration", snippet(cx, pattern_span, "_")),
-                           |db| { db.span_note(prev_span, "previous binding is here"); });
+                           |db| {
+            db.span_note(prev_span, "previous binding is here");
+        });
     }
 }
 

clippy_lints/src/utils/sugg.rs

@@ -258,9 +258,8 @@ pub fn make_assoc(op: AssocOp, lhs: &Sugg, rhs: &Sugg) -> Sugg<'static> {
     fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
         other.precedence() < op.precedence() ||
         (other.precedence() == op.precedence() &&
-         ((op != other && associativity(op) != dir) ||
-          (op == other && associativity(op) != Associativity::Both))) || is_shift(op) && is_arith(other) ||
-        is_shift(other) && is_arith(op)
+         ((op != other && associativity(op) != dir) || (op == other && associativity(op) != Associativity::Both))) ||
+        is_shift(op) && is_arith(other) || is_shift(other) && is_arith(op)
     }
 
     let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {

clippy_lints/src/vec.rs

@@ -81,11 +81,9 @@ fn check_vec_macro(cx: &LateContext, vec_args: &higher::VecArgs, span: Span) {
         },
     };
 
-    span_lint_and_then(cx,
-                       USELESS_VEC,
-                       span,
-                       "useless use of `vec!`",
-                       |db| { db.span_suggestion(span, "you can use a slice directly", snippet); });
+    span_lint_and_then(cx, USELESS_VEC, span, "useless use of `vec!`", |db| {
+        db.span_suggestion(span, "you can use a slice directly", snippet);
+    });
 }
 
 /// Return the item type of the vector (ie. the `T` in `Vec<T>`).