Auto merge of #12798 - Alexendoo:no-effect-path-statements, r=y21

Don't lint path statements in no_effect

The rustc lint `path_statements` covers this case

Fixes #11547

changelog: none

Author: bors

clippy_lints/src/no_effect.rs

@@ -94,7 +94,6 @@ impl<'tcx> LateLintPass<'tcx> for NoEffect {
 
     fn check_block_post(&mut self, cx: &LateContext<'tcx>, _: &'tcx rustc_hir::Block<'tcx>) {
         for hir_id in self.local_bindings.pop().unwrap() {
-            // FIXME(rust/#120456) - is `swap_remove` correct?
             if let Some(span) = self.underscore_bindings.swap_remove(&hir_id) {
                 span_lint_hir(
                     cx,
@@ -109,7 +108,6 @@ impl<'tcx> LateLintPass<'tcx> for NoEffect {
 
     fn check_expr(&mut self, _: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
         if let Some(def_id) = path_to_local(expr) {
-            // FIXME(rust/#120456) - is `swap_remove` correct?
             self.underscore_bindings.swap_remove(&def_id);
         }
     }
@@ -118,7 +116,11 @@ impl<'tcx> LateLintPass<'tcx> for NoEffect {
 impl NoEffect {
     fn check_no_effect(&mut self, cx: &LateContext<'_>, stmt: &Stmt<'_>) -> bool {
         if let StmtKind::Semi(expr) = stmt.kind {
-            // move `expr.span.from_expansion()` ahead
+            // Covered by rustc `path_statements` lint
+            if matches!(expr.kind, ExprKind::Path(_)) {
+                return true;
+            }
+
             if expr.span.from_expansion() {
                 return false;
             }

tests/ui/no_effect.rs

@@ -1,6 +1,5 @@
 #![feature(fn_traits, unboxed_closures)]
 #![warn(clippy::no_effect_underscore_binding)]
-#![allow(dead_code, path_statements)]
 #![allow(
     clippy::deref_addrof,
     clippy::redundant_field_names,
@@ -33,7 +32,6 @@ impl Neg for Cout {
     }
 }
 
-struct Unit;
 struct Tuple(i32);
 struct Struct {
     field: i32,
@@ -42,10 +40,6 @@ enum Enum {
     Tuple(i32),
     Struct { field: i32 },
 }
-struct DropUnit;
-impl Drop for DropUnit {
-    fn drop(&mut self) {}
-}
 struct DropStruct {
     field: i32,
 }
@@ -117,15 +111,9 @@ impl FnOnce<(&str,)> for GreetStruct3 {
 
 fn main() {
     let s = get_struct();
-    let s2 = get_struct();
 
     0;
     //~^ ERROR: statement with no effect
-    //~| NOTE: `-D clippy::no-effect` implied by `-D warnings`
-    s2;
-    //~^ ERROR: statement with no effect
-    Unit;
-    //~^ ERROR: statement with no effect
     Tuple(0);
     //~^ ERROR: statement with no effect
     Struct { field: 0 };
@@ -192,7 +180,6 @@ fn main() {
     unsafe { unsafe_fn() };
     let _used = get_struct();
     let _x = vec![1];
-    DropUnit;
     DropStruct { field: 0 };
     DropTuple(0);
     DropEnum::Tuple(0);

tests/ui/no_effect.stderr

@@ -1,5 +1,5 @@
 error: statement with no effect
-  --> tests/ui/no_effect.rs:122:5
+  --> tests/ui/no_effect.rs:115:5
    |
 LL |     0;
    |     ^^
@@ -8,151 +8,139 @@ LL |     0;
    = help: to override `-D warnings` add `#[allow(clippy::no_effect)]`
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:125:5
-   |
-LL |     s2;
-   |     ^^^
-
-error: statement with no effect
-  --> tests/ui/no_effect.rs:127:5
-   |
-LL |     Unit;
-   |     ^^^^^
-
-error: statement with no effect
-  --> tests/ui/no_effect.rs:129:5
+  --> tests/ui/no_effect.rs:117:5
    |
 LL |     Tuple(0);
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:131:5
+  --> tests/ui/no_effect.rs:119:5
    |
 LL |     Struct { field: 0 };
    |     ^^^^^^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:133:5
+  --> tests/ui/no_effect.rs:121:5
    |
 LL |     Struct { ..s };
    |     ^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:135:5
+  --> tests/ui/no_effect.rs:123:5
    |
 LL |     Union { a: 0 };
    |     ^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:137:5
+  --> tests/ui/no_effect.rs:125:5
    |
 LL |     Enum::Tuple(0);
    |     ^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:139:5
+  --> tests/ui/no_effect.rs:127:5
    |
 LL |     Enum::Struct { field: 0 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:141:5
+  --> tests/ui/no_effect.rs:129:5
    |
 LL |     5 + 6;
    |     ^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:143:5
+  --> tests/ui/no_effect.rs:131:5
    |
 LL |     *&42;
    |     ^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:145:5
+  --> tests/ui/no_effect.rs:133:5
    |
 LL |     &6;
    |     ^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:147:5
+  --> tests/ui/no_effect.rs:135:5
    |
 LL |     (5, 6, 7);
    |     ^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:149:5
+  --> tests/ui/no_effect.rs:137:5
    |
 LL |     ..;
    |     ^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:151:5
+  --> tests/ui/no_effect.rs:139:5
    |
 LL |     5..;
    |     ^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:153:5
+  --> tests/ui/no_effect.rs:141:5
    |
 LL |     ..5;
    |     ^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:155:5
+  --> tests/ui/no_effect.rs:143:5
    |
 LL |     5..6;
    |     ^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:157:5
+  --> tests/ui/no_effect.rs:145:5
    |
 LL |     5..=6;
    |     ^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:159:5
+  --> tests/ui/no_effect.rs:147:5
    |
 LL |     [42, 55];
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:161:5
+  --> tests/ui/no_effect.rs:149:5
    |
 LL |     [42, 55][1];
    |     ^^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:163:5
+  --> tests/ui/no_effect.rs:151:5
    |
 LL |     (42, 55).1;
    |     ^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:165:5
+  --> tests/ui/no_effect.rs:153:5
    |
 LL |     [42; 55];
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:167:5
+  --> tests/ui/no_effect.rs:155:5
    |
 LL |     [42; 55][13];
    |     ^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:170:5
+  --> tests/ui/no_effect.rs:158:5
    |
 LL |     || x += 5;
    |     ^^^^^^^^^^
 
 error: statement with no effect
-  --> tests/ui/no_effect.rs:173:5
+  --> tests/ui/no_effect.rs:161:5
    |
 LL |     FooString { s: s };
    |     ^^^^^^^^^^^^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> tests/ui/no_effect.rs:175:9
+  --> tests/ui/no_effect.rs:163:9
    |
 LL |     let _unused = 1;
    |         ^^^^^^^
@@ -161,22 +149,22 @@ LL |     let _unused = 1;
    = help: to override `-D warnings` add `#[allow(clippy::no_effect_underscore_binding)]`
 
 error: binding to `_` prefixed variable with no side-effect
-  --> tests/ui/no_effect.rs:178:9
+  --> tests/ui/no_effect.rs:166:9
    |
 LL |     let _penguin = || println!("Some helpful closure");
    |         ^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> tests/ui/no_effect.rs:180:9
+  --> tests/ui/no_effect.rs:168:9
    |
 LL |     let _duck = Struct { field: 0 };
    |         ^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> tests/ui/no_effect.rs:182:9
+  --> tests/ui/no_effect.rs:170:9
    |
 LL |     let _cat = [2, 4, 6, 8][2];
    |         ^^^^
 
-error: aborting due to 29 previous errors
+error: aborting due to 27 previous errors