use rustc::lint::*;
+use rustc::ty;
use rustc_front::hir::*;
-use utils::{get_parent_expr, in_macro, is_block_equal, is_exp_equal, span_lint, span_note_and_lint};
+use std::collections::HashMap;
+use std::collections::hash_map::Entry;
+use syntax::parse::token::InternedString;
+use syntax::util::small_vector::SmallVector;
+use utils::{SpanlessEq, SpanlessHash};
+use utils::{get_parent_expr, in_macro, span_note_and_lint};
/// **What it does:** This lint checks for consecutive `ifs` with the same condition. This lint is
/// `Warn` by default.
"if with the same *then* and *else* blocks"
}
+/// **What it does:** This lint checks for `match` with identical arm bodies.
+///
+/// **Why is this bad?** This is probably a copy & paste error. If arm bodies are the same on
+/// purpose, you can factor them
+/// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
+///
+/// **Known problems:** Hopefully none.
+///
+/// **Example:**
+/// ```rust,ignore
+/// match foo {
+/// Bar => bar(),
+/// Quz => quz(),
+/// Baz => bar(), // <= oops
+/// }
+/// ```
+declare_lint! {
+ pub MATCH_SAME_ARMS,
+ Warn,
+ "`match` with identical arm bodies"
+}
+
#[derive(Copy, Clone, Debug)]
pub struct CopyAndPaste;
impl LintPass for CopyAndPaste {
fn get_lints(&self) -> LintArray {
- lint_array![
- IFS_SAME_COND,
- IF_SAME_THEN_ELSE
- ]
+ lint_array![IFS_SAME_COND, IF_SAME_THEN_ELSE, MATCH_SAME_ARMS]
}
}
impl LateLintPass for CopyAndPaste {
fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if !in_macro(cx, expr.span) {
- lint_same_then_else(cx, expr);
- lint_same_cond(cx, expr);
+ // skip ifs directly in else, it will be checked in the parent if
+ if let Some(&Expr{node: ExprIf(_, _, Some(ref else_expr)), ..}) = get_parent_expr(cx, expr) {
+ if else_expr.id == expr.id {
+ return;
+ }
+ }
+
+ let (conds, blocks) = if_sequence(expr);
+ lint_same_then_else(cx, blocks.as_slice());
+ lint_same_cond(cx, conds.as_slice());
+ lint_match_arms(cx, expr);
}
}
}
/// Implementation of `IF_SAME_THEN_ELSE`.
-fn lint_same_then_else(cx: &LateContext, expr: &Expr) {
- if let ExprIf(_, ref then_block, Some(ref else_expr)) = expr.node {
- if let ExprBlock(ref else_block) = else_expr.node {
- if is_block_equal(cx, &then_block, &else_block, false) {
- span_lint(cx, IF_SAME_THEN_ELSE, expr.span, "this if has the same then and else blocks");
- }
- }
+fn lint_same_then_else(cx: &LateContext, blocks: &[&Block]) {
+ let hash: &Fn(&&Block) -> u64 = &|block| -> u64 {
+ let mut h = SpanlessHash::new(cx);
+ h.hash_block(block);
+ h.finish()
+ };
+
+ let eq: &Fn(&&Block, &&Block) -> bool = &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).eq_block(lhs, rhs) };
+
+ if let Some((i, j)) = search_same(blocks, hash, eq) {
+ span_note_and_lint(cx,
+ IF_SAME_THEN_ELSE,
+ j.span,
+ "this `if` has identical blocks",
+ i.span,
+ "same as this");
}
}
/// Implementation of `IFS_SAME_COND`.
-fn lint_same_cond(cx: &LateContext, expr: &Expr) {
- // skip ifs directly in else, it will be checked in the parent if
- if let Some(&Expr{node: ExprIf(_, _, Some(ref else_expr)), ..}) = get_parent_expr(cx, expr) {
- if else_expr.id == expr.id {
- return;
- }
+fn lint_same_cond(cx: &LateContext, conds: &[&Expr]) {
+ let hash: &Fn(&&Expr) -> u64 = &|expr| -> u64 {
+ let mut h = SpanlessHash::new(cx);
+ h.hash_expr(expr);
+ h.finish()
+ };
+
+ let eq: &Fn(&&Expr, &&Expr) -> bool = &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) };
+
+ if let Some((i, j)) = search_same(conds, hash, eq) {
+ span_note_and_lint(cx,
+ IFS_SAME_COND,
+ j.span,
+ "this `if` has the same condition as a previous if",
+ i.span,
+ "same as this");
}
+}
- let conds = condition_sequence(expr);
+/// Implementation if `MATCH_SAME_ARMS`.
+fn lint_match_arms(cx: &LateContext, expr: &Expr) {
+ let hash = |arm: &Arm| -> u64 {
+ let mut h = SpanlessHash::new(cx);
+ h.hash_expr(&arm.body);
+ h.finish()
+ };
- for (n, i) in conds.iter().enumerate() {
- for j in conds.iter().skip(n+1) {
- if is_exp_equal(cx, i, j, true) {
- span_note_and_lint(cx, IFS_SAME_COND, j.span, "this if has the same condition as a previous if", i.span, "same as this");
- }
+ let eq = |lhs: &Arm, rhs: &Arm| -> bool {
+ // Arms with a guard are ignored, those can’t always be merged together
+ lhs.guard.is_none() && rhs.guard.is_none() &&
+ SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) &&
+ // all patterns should have the same bindings
+ bindings(cx, &lhs.pats[0]) == bindings(cx, &rhs.pats[0])
+ };
+
+ if let ExprMatch(_, ref arms, MatchSource::Normal) = expr.node {
+ if let Some((i, j)) = search_same(&arms, hash, eq) {
+ span_note_and_lint(cx,
+ MATCH_SAME_ARMS,
+ j.body.span,
+ "this `match` has identical arm bodies",
+ i.body.span,
+ "same as this");
}
}
}
-/// Return the list of condition expressions in a sequence of `if/else`.
-/// Eg. would return `[a, b]` for the expression `if a {..} else if b {..}`.
-fn condition_sequence(mut expr: &Expr) -> Vec<&Expr> {
- let mut result = vec![];
+/// Return the list of condition expressions and the list of blocks in a sequence of `if/else`.
+/// Eg. would return `([a, b], [c, d, e])` for the expression
+/// `if a { c } else if b { d } else { e }`.
+fn if_sequence(mut expr: &Expr) -> (SmallVector<&Expr>, SmallVector<&Block>) {
+ let mut conds = SmallVector::zero();
+ let mut blocks = SmallVector::zero();
- while let ExprIf(ref cond, _, ref else_expr) = expr.node {
- result.push(&**cond);
+ while let ExprIf(ref cond, ref then_block, ref else_expr) = expr.node {
+ conds.push(&**cond);
+ blocks.push(&**then_block);
if let Some(ref else_expr) = *else_expr {
expr = else_expr;
- }
- else {
+ } else {
break;
}
}
+ // final `else {..}`
+ if !blocks.is_empty() {
+ if let ExprBlock(ref block) = expr.node {
+ blocks.push(&**block);
+ }
+ }
+
+ (conds, blocks)
+}
+
+/// Return the list of bindings in a pattern.
+fn bindings<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat) -> HashMap<InternedString, ty::Ty<'tcx>> {
+ fn bindings_impl<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat, map: &mut HashMap<InternedString, ty::Ty<'tcx>>) {
+ match pat.node {
+ PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
+ PatKind::TupleStruct(_, Some(ref pats)) => {
+ for pat in pats {
+ bindings_impl(cx, pat, map);
+ }
+ }
+ PatKind::Ident(_, ref ident, ref as_pat) => {
+ if let Entry::Vacant(v) = map.entry(ident.node.name.as_str()) {
+ v.insert(cx.tcx.pat_ty(pat));
+ }
+ if let Some(ref as_pat) = *as_pat {
+ bindings_impl(cx, as_pat, map);
+ }
+ }
+ PatKind::Struct(_, ref fields, _) => {
+ for pat in fields {
+ bindings_impl(cx, &pat.node.pat, map);
+ }
+ }
+ PatKind::Tup(ref fields) => {
+ for pat in fields {
+ bindings_impl(cx, pat, map);
+ }
+ }
+ PatKind::Vec(ref lhs, ref mid, ref rhs) => {
+ for pat in lhs {
+ bindings_impl(cx, pat, map);
+ }
+ if let Some(ref mid) = *mid {
+ bindings_impl(cx, mid, map);
+ }
+ for pat in rhs {
+ bindings_impl(cx, pat, map);
+ }
+ }
+ PatKind::TupleStruct(..) |
+ PatKind::Lit(..) |
+ PatKind::QPath(..) |
+ PatKind::Range(..) |
+ PatKind::Wild |
+ PatKind::Path(..) => (),
+ }
+ }
+
+ let mut result = HashMap::new();
+ bindings_impl(cx, pat, &mut result);
result
}
+
+fn search_same<T, Hash, Eq>(exprs: &[T], hash: Hash, eq: Eq) -> Option<(&T, &T)>
+ where Hash: Fn(&T) -> u64,
+ Eq: Fn(&T, &T) -> bool
+{
+ // common cases
+ if exprs.len() < 2 {
+ return None;
+ } else if exprs.len() == 2 {
+ return if eq(&exprs[0], &exprs[1]) {
+ Some((&exprs[0], &exprs[1]))
+ } else {
+ None
+ };
+ }
+
+ let mut map: HashMap<_, Vec<&_>> = HashMap::with_capacity(exprs.len());
+
+ for expr in exprs {
+ match map.entry(hash(expr)) {
+ Entry::Occupied(o) => {
+ for o in o.get() {
+ if eq(&o, expr) {
+ return Some((&o, expr));
+ }
+ }
+ }
+ Entry::Vacant(v) => {
+ v.insert(vec![expr]);
+ }
+ }
+ }
+
+ None
+}
projects / rust.git / blobdiff