Auto merge of #4246 - mikerite:fix-4244, r=flip1995

Fix `match_same_arms` false negative Closes #4244 changelog: Fix `match_same_arms` false negative
rust-lang · Jul 2, 2019 · be3d6cf · be3d6cf
2 parents cc8b221 + c199d90
commit be3d6cf
Show file tree

Hide file tree

Showing 3 changed files with 53 additions and 5 deletions.
diff --git a/clippy_lints/src/copies.rs b/clippy_lints/src/copies.rs
@@ -1,4 +1,6 @@
-use crate::utils::{get_parent_expr, higher, in_macro_or_desugar, snippet, span_lint_and_then, span_note_and_lint};
+use crate::utils::{
+ get_parent_expr, higher, in_macro_or_desugar, same_tys, snippet, span_lint_and_then, span_note_and_lint,
+};
 use crate::utils::{SpanlessEq, SpanlessHash};
 use rustc::hir::*;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
@@ -165,7 +167,18 @@ fn lint_same_cond(cx: &LateContext<'_, '_>, conds: &[&Expr]) {
 }
 
 /// Implementation of `MATCH_SAME_ARMS`.
-fn lint_match_arms(cx: &LateContext<'_, '_>, expr: &Expr) {
+fn lint_match_arms<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr) {
+ fn same_bindings<'tcx>(
+ cx: &LateContext<'_, 'tcx>,
+ lhs: &FxHashMap<LocalInternedString, Ty<'tcx>>,
+ rhs: &FxHashMap<LocalInternedString, Ty<'tcx>>,
+ ) -> bool {
+ lhs.len() == rhs.len()
+ && lhs
+ .iter()
+ .all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| same_tys(cx, l_ty, r_ty)))
+ }
+
  if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.node {
  let hash = |&(_, arm): &(usize, &Arm)| -> u64 {
  let mut h = SpanlessHash::new(cx, cx.tables);
@@ -176,12 +189,13 @@ fn lint_match_arms(cx: &LateContext<'_, '_>, expr: &Expr) {
  let eq = |&(lindex, lhs): &(usize, &Arm), &(rindex, rhs): &(usize, &Arm)| -> bool {
  let min_index = usize::min(lindex, rindex);
  let max_index = usize::max(lindex, rindex);
+
  // Arms with a guard are ignored, those can’t always be merged together
  // This is also the case for arms in-between each there is an arm with a guard
  (min_index..=max_index).all(|index| arms[index].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])
+ same_bindings(cx, &bindings(cx, &lhs.pats[0]), &bindings(cx, &rhs.pats[0]))
  };
 
  let indexed_arms: Vec<(usize, &Arm)> = arms.iter().enumerate().collect();

diff --git a/tests/ui/match_same_arms.rs b/tests/ui/match_same_arms.rs
@@ -1,3 +1,4 @@
+#![warn(clippy::match_same_arms)]
 #![allow(
  clippy::blacklisted_name,
  clippy::collapsible_if,
@@ -21,7 +22,6 @@ pub enum Abc {
  C,
 }
 
-#[warn(clippy::match_same_arms)]
 #[allow(clippy::unused_unit)]
 fn match_same_arms() {
  let _ = match 42 {
@@ -126,4 +126,21 @@ fn match_same_arms() {
  };
 }
 
+mod issue4244 {
+ #[derive(PartialEq, PartialOrd, Eq, Ord)]
+ pub enum CommandInfo {
+ BuiltIn { name: String, about: Option<String> },
+ External { name: String, path: std::path::PathBuf },
+ }
+
+ impl CommandInfo {
+ pub fn name(&self) -> String {
+ match self {
+ CommandInfo::BuiltIn { name, .. } => name.to_string(),
+ CommandInfo::External { name, .. } => name.to_string(),
+ }
+ }
+ }
+}
+
 fn main() {}
diff --git a/tests/ui/match_same_arms.stderr b/tests/ui/match_same_arms.stderr
@@ -224,5 +224,22 @@ help: consider refactoring into `2 | 3`
 LL | 2 => 2, //~ ERROR 2nd matched arms have same body
  | ^
 
-error: aborting due to 12 previous errors
+error: this `match` has identical arm bodies
+ --> $DIR/match_same_arms.rs:140:55
+ |
+LL | CommandInfo::External { name, .. } => name.to_string(),
+ | ^^^^^^^^^^^^^^^^
+ |
+note: same as this
+ --> $DIR/match_same_arms.rs:139:54
+ |
+LL | CommandInfo::BuiltIn { name, .. } => name.to_string(),
+ | ^^^^^^^^^^^^^^^^
+help: consider refactoring into `CommandInfo::BuiltIn { name, .. } | CommandInfo::External { name, .. }`
+ --> $DIR/match_same_arms.rs:139:17
+ |
+LL | CommandInfo::BuiltIn { name, .. } => name.to_string(),
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 13 previous errors