Don't show no_effect warning on unit structs implementing fn_once

rust-lang · Oct 29, 2021 · 2645f42 · 2645f42
1 parent dbe167d
commit 2645f42
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Showing 3 changed files with 75 additions and 41 deletions.
diff --git a/clippy_lints/src/no_effect.rs b/clippy_lints/src/no_effect.rs
@@ -3,6 +3,7 @@ use clippy_utils::is_lint_allowed;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::has_drop;
 use rustc_errors::Applicability;
+use rustc_hir::def::CtorKind;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{is_range_literal, BinOpKind, BlockCheckMode, Expr, ExprKind, PatKind, Stmt, StmtKind, UnsafeSource};
 use rustc_lint::{LateContext, LateLintPass};
@@ -130,10 +131,12 @@ fn has_no_effect(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
         },
         ExprKind::Call(callee, args) => {
             if let ExprKind::Path(ref qpath) = callee.kind {
-                let res = cx.qpath_res(qpath, callee.hir_id);
                 let def_matched = matches!(
-                    res,
-                    Res::Def(DefKind::Struct | DefKind::Variant | DefKind::Ctor(..), ..)
+                    cx.qpath_res(qpath, callee.hir_id),
+                    Res::Def(
+                        DefKind::Struct | DefKind::Variant | DefKind::Ctor(_, CtorKind::Fn | CtorKind::Fictive),
+                        ..
+                    )
                 );
                 if def_matched || is_range_literal(expr) {
                     !has_drop(cx, cx.typeck_results().expr_ty(expr)) && args.iter().all(|arg| has_no_effect(cx, arg))
@@ -235,13 +238,11 @@ fn reduce_expression<'a>(cx: &LateContext<'_>, expr: &'a Expr<'a>) -> Option<Vec
         },
         ExprKind::Call(callee, args) => {
             if let ExprKind::Path(ref qpath) = callee.kind {
-                let res = cx.qpath_res(qpath, callee.hir_id);
-                match res {
-                    Res::Def(DefKind::Struct | DefKind::Variant | DefKind::Ctor(..), ..)
-                        if !has_drop(cx, cx.typeck_results().expr_ty(expr)) =>
-                    {
-                        Some(args.iter().collect())
-                    },
+                match cx.qpath_res(qpath, callee.hir_id) {
+                    Res::Def(
+                        DefKind::Struct | DefKind::Variant | DefKind::Ctor(_, CtorKind::Fn | CtorKind::Fictive),
+                        ..,
+                    ) if !has_drop(cx, cx.typeck_results().expr_ty(expr)) => Some(args.iter().collect()),
                     _ => None,
                 }
             } else {

diff --git a/tests/ui/no_effect.rs b/tests/ui/no_effect.rs
@@ -1,4 +1,4 @@
-#![feature(box_syntax)]
+#![feature(box_syntax, fn_traits, unboxed_closures)]
 #![warn(clippy::no_effect_underscore_binding)]
 #![allow(dead_code)]
 #![allow(path_statements)]
@@ -58,6 +58,36 @@ unsafe fn unsafe_fn() -> i32 {
     0
 }
 
+struct GreetStruct1;
+
+impl FnOnce<(&str,)> for GreetStruct1 {
+    type Output = ();
+
+    extern "rust-call" fn call_once(self, (who,): (&str,)) -> Self::Output {
+        println!("hello {}", who);
+    }
+}
+
+struct GreetStruct2();
+
+impl FnOnce<(&str,)> for GreetStruct2 {
+    type Output = ();
+
+    extern "rust-call" fn call_once(self, (who,): (&str,)) -> Self::Output {
+        println!("hello {}", who);
+    }
+}
+
+struct GreetStruct3 {}
+
+impl FnOnce<(&str,)> for GreetStruct3 {
+    type Output = ();
+
+    extern "rust-call" fn call_once(self, (who,): (&str,)) -> Self::Output {
+        println!("hello {}", who);
+    }
+}
+
 fn main() {
     let s = get_struct();
     let s2 = get_struct();
@@ -108,4 +138,7 @@ fn main() {
     DropTuple(0);
     DropEnum::Tuple(0);
     DropEnum::Struct { field: 0 };
+    GreetStruct1("world");
+    GreetStruct2()("world");
+    GreetStruct3 {}("world");
 }
diff --git a/tests/ui/no_effect.stderr b/tests/ui/no_effect.stderr
@@ -1,183 +1,183 @@
 error: statement with no effect
-  --> $DIR/no_effect.rs:65:5
+  --> $DIR/no_effect.rs:95:5
    |
 LL |     0;
    |     ^^
    |
    = note: `-D clippy::no-effect` implied by `-D warnings`
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:66:5
+  --> $DIR/no_effect.rs:96:5
    |
 LL |     s2;
    |     ^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:67:5
+  --> $DIR/no_effect.rs:97:5
    |
 LL |     Unit;
    |     ^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:68:5
+  --> $DIR/no_effect.rs:98:5
    |
 LL |     Tuple(0);
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:69:5
+  --> $DIR/no_effect.rs:99:5
    |
 LL |     Struct { field: 0 };
    |     ^^^^^^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:70:5
+  --> $DIR/no_effect.rs:100:5
    |
 LL |     Struct { ..s };
    |     ^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:71:5
+  --> $DIR/no_effect.rs:101:5
    |
 LL |     Union { a: 0 };
    |     ^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:72:5
+  --> $DIR/no_effect.rs:102:5
    |
 LL |     Enum::Tuple(0);
    |     ^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:73:5
+  --> $DIR/no_effect.rs:103:5
    |
 LL |     Enum::Struct { field: 0 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:74:5
+  --> $DIR/no_effect.rs:104:5
    |
 LL |     5 + 6;
    |     ^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:75:5
+  --> $DIR/no_effect.rs:105:5
    |
 LL |     *&42;
    |     ^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:76:5
+  --> $DIR/no_effect.rs:106:5
    |
 LL |     &6;
    |     ^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:77:5
+  --> $DIR/no_effect.rs:107:5
    |
 LL |     (5, 6, 7);
    |     ^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:78:5
+  --> $DIR/no_effect.rs:108:5
    |
 LL |     box 42;
    |     ^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:79:5
+  --> $DIR/no_effect.rs:109:5
    |
 LL |     ..;
    |     ^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:80:5
+  --> $DIR/no_effect.rs:110:5
    |
 LL |     5..;
    |     ^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:81:5
+  --> $DIR/no_effect.rs:111:5
    |
 LL |     ..5;
    |     ^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:82:5
+  --> $DIR/no_effect.rs:112:5
    |
 LL |     5..6;
    |     ^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:83:5
+  --> $DIR/no_effect.rs:113:5
    |
 LL |     5..=6;
    |     ^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:84:5
+  --> $DIR/no_effect.rs:114:5
    |
 LL |     [42, 55];
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:85:5
+  --> $DIR/no_effect.rs:115:5
    |
 LL |     [42, 55][1];
    |     ^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:86:5
+  --> $DIR/no_effect.rs:116:5
    |
 LL |     (42, 55).1;
    |     ^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:87:5
+  --> $DIR/no_effect.rs:117:5
    |
 LL |     [42; 55];
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:88:5
+  --> $DIR/no_effect.rs:118:5
    |
 LL |     [42; 55][13];
    |     ^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:90:5
+  --> $DIR/no_effect.rs:120:5
    |
 LL |     || x += 5;
    |     ^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:92:5
+  --> $DIR/no_effect.rs:122:5
    |
 LL |     FooString { s: s };
    |     ^^^^^^^^^^^^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:93:5
+  --> $DIR/no_effect.rs:123:5
    |
 LL |     let _unused = 1;
    |     ^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::no-effect-underscore-binding` implied by `-D warnings`
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:94:5
+  --> $DIR/no_effect.rs:124:5
    |
 LL |     let _penguin = || println!("Some helpful closure");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:95:5
+  --> $DIR/no_effect.rs:125:5
    |
 LL |     let _duck = Struct { field: 0 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:96:5
+  --> $DIR/no_effect.rs:126:5
    |
 LL |     let _cat = [2, 4, 6, 8][2];
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^