make sure they have the same type

Author: Centri3

clippy_lints/src/matches/redundant_guard.rs

@@ -47,12 +47,9 @@ pub(super) fn check(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
                 arm.guard,
                 &mut app,
             );
-
-            continue;
         }
-
         // `Some(x) if let Some(2) = x`
-        if let Guard::IfLet(let_expr) = guard
+        else if let Guard::IfLet(let_expr) = guard
             && let pat = let_expr.pat
             && let Some((pat_binding, field_name)) = get_pat_binding(cx, let_expr.init, outer_arm)
         {
@@ -66,16 +63,20 @@ pub(super) fn check(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
                 None,
                 &mut app,
             );
-
-            continue;
         }
-
         // `Some(x) if x == Some(2)`
-        if let Guard::If(if_expr) = guard
+        else if let Guard::If(if_expr) = guard
             && let ExprKind::Binary(bin_op, local, pat) = if_expr.kind
             && matches!(bin_op.node, BinOpKind::Eq)
             && let Some((pat_binding, field_name)) = get_pat_binding(cx, local, outer_arm)
             && expr_can_be_pat(cx, pat)
+            // Ensure they have the same type. If they don't, we'd need deref coercion which isn't
+            // possible (currently) in a pattern. In some cases, you can use something like
+            // `as_deref` or similar but in general, we shouldn't lint this as it'd create an
+            // extraordinary amount of FPs.
+            //
+            // This isn't necessary in the other two checks, as they must be a pattern already.
+            && cx.typeck_results().expr_ty(local) == cx.typeck_results().expr_ty(pat)
         {
             emit_redundant_guard(
                 cx,
@@ -87,8 +88,6 @@ pub(super) fn check(cx: &LateContext<'_>, arms: &[Arm<'_>]) {
                 None,
                 &mut app,
             );
-
-            continue;
         }
     }
 }
@@ -198,52 +197,30 @@ fn emit_redundant_guard(
 
 /// Checks if the given `Expr` can also be represented as a `Pat`.
 fn expr_can_be_pat(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
-    fn helper(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
-        for_each_expr(expr, |expr| {
-            let expr = expr.peel_blocks();
-            if match expr.kind {
-                ExprKind::ConstBlock(..) => cx.tcx.features().inline_const_pat,
-                ExprKind::Call(c, ..) if let ExprKind::Path(qpath) = c.kind => {
-                    // Allow ctors
-                    matches!(cx.qpath_res(&qpath, c.hir_id), Res::Def(DefKind::Ctor(..), ..))
-                },
-                ExprKind::AddrOf(.., expr) => helper(cx, expr),
-                ExprKind::Array(exprs) | ExprKind::Tup(exprs) => {
-                    for expr in exprs {
-                        if !helper(cx, expr) {
-                            return ControlFlow::Break(());
-                        }
-                    }
-
-                    true
-                },
-                ExprKind::Struct(_, fields, rest) => {
-                    for field in fields {
-                        if !helper(cx, field.expr) {
-                            return ControlFlow::Break(());
-                        }
-                    }
-
-                    if rest.is_some() {
-                        return ControlFlow::Break(());
-                    }
-
-                    true
-                },
-                ExprKind::Path(qpath) => {
-                    // Can't compare a local with another local in a pat
-                    !matches!(cx.qpath_res(&qpath, expr.hir_id), Res::Local(..))
-                },
-                ExprKind::Lit(..) => true,
-                _ => false,
-            } {
-                return ControlFlow::Continue(());
-            }
-
-            ControlFlow::Break(())
-        })
-        .is_none()
-    }
+    for_each_expr(expr, |expr| {
+        if match expr.kind {
+            ExprKind::ConstBlock(..) => cx.tcx.features().inline_const_pat,
+            ExprKind::Call(c, ..) if let ExprKind::Path(qpath) = c.kind => {
+                // Allow ctors
+                matches!(cx.qpath_res(&qpath, c.hir_id), Res::Def(DefKind::Ctor(..), ..))
+            },
+            ExprKind::Path(qpath) => {
+                matches!(
+                    cx.qpath_res(&qpath, expr.hir_id),
+                    Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Ctor(..), ..),
+                )
+            },
+            ExprKind::AddrOf(..)
+            | ExprKind::Array(..)
+            | ExprKind::Tup(..)
+            | ExprKind::Struct(..)
+            | ExprKind::Lit(..) => true,
+            _ => false,
+        } {
+            return ControlFlow::Continue(());
+        }
 
-    helper(cx, expr)
+        ControlFlow::Break(())
+    })
+    .is_none()
 }

tests/ui/redundant_guard.fixed

@@ -56,6 +56,12 @@ fn main() {
         B { e: Some(A(2)) } => ..,
         _ => todo!(),
     };
+    // Do not lint, since we cannot represent this as a pattern (at least, without a conversion)
+    let v = Some(vec![1u8, 2, 3]);
+    match v {
+        Some(x) if x == [1] => {},
+        _ => {},
+    }
 
     external! {
         let x = Some(Some(1));
@@ -73,3 +79,33 @@ fn main() {
         };
     }
 }
+
+// Do not lint
+
+fn f(s: Option<std::ffi::OsString>) {
+    match s {
+        Some(x) if x == "a" => {},
+        _ => {},
+    }
+}
+
+struct S {
+    a: usize,
+}
+
+impl PartialEq for S {
+    fn eq(&self, _: &Self) -> bool {
+        true
+    }
+}
+
+impl Eq for S {}
+
+static CONST_S: S = S { a: 1 };
+
+fn g(opt_s: Option<S>) {
+    match opt_s {
+        Some(x) if x == CONST_S => {},
+        _ => {},
+    }
+}

tests/ui/redundant_guard.rs

@@ -56,6 +56,12 @@ fn main() {
         B { e } if matches!(e, Some(A(2))) => ..,
         _ => todo!(),
     };
+    // Do not lint, since we cannot represent this as a pattern (at least, without a conversion)
+    let v = Some(vec![1u8, 2, 3]);
+    match v {
+        Some(x) if x == [1] => {},
+        _ => {},
+    }
 
     external! {
         let x = Some(Some(1));
@@ -73,3 +79,33 @@ fn main() {
         };
     }
 }
+
+// Do not lint
+
+fn f(s: Option<std::ffi::OsString>) {
+    match s {
+        Some(x) if x == "a" => {},
+        _ => {},
+    }
+}
+
+struct S {
+    a: usize,
+}
+
+impl PartialEq for S {
+    fn eq(&self, _: &Self) -> bool {
+        true
+    }
+}
+
+impl Eq for S {}
+
+static CONST_S: S = S { a: 1 };
+
+fn g(opt_s: Option<S>) {
+    match opt_s {
+        Some(x) if x == CONST_S => {},
+        _ => {},
+    }
+}