fix(zero_repeat_side_effects): better identify exprs with side effects

Author: ada4a

clippy_lints/src/zero_repeat_side_effects.rs

@@ -1,7 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::higher::VecArgs;
 use clippy_utils::source::snippet;
-use clippy_utils::visitors::for_each_expr_without_closures;
 use rustc_ast::LitKind;
 use rustc_data_structures::packed::Pu128;
 use rustc_errors::Applicability;
@@ -11,7 +10,7 @@ use rustc_session::declare_lint_pass;
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for array or vec initializations which call a function or method,
+    /// Checks for array or vec initializations which contain an expression with side effects,
     /// but which have a repeat count of zero.
     ///
     /// ### Why is this bad?
@@ -71,15 +70,7 @@ impl LateLintPass<'_> for ZeroRepeatSideEffects {
 
 fn inner_check(cx: &LateContext<'_>, expr: &'_ rustc_hir::Expr<'_>, inner_expr: &'_ rustc_hir::Expr<'_>, is_vec: bool) {
     // check if expr is a call or has a call inside it
-    if for_each_expr_without_closures(inner_expr, |x| {
-        if let ExprKind::Call(_, _) | ExprKind::MethodCall(_, _, _, _) = x.kind {
-            std::ops::ControlFlow::Break(())
-        } else {
-            std::ops::ControlFlow::Continue(())
-        }
-    })
-    .is_some()
-    {
+    if inner_expr.can_have_side_effects() {
         let parent_hir_node = cx.tcx.parent_hir_node(expr.hir_id);
         let return_type = cx.typeck_results().expr_ty(expr);
 
@@ -107,7 +98,7 @@ fn inner_check(cx: &LateContext<'_>, expr: &'_ rustc_hir::Expr<'_>, inner_expr:
             cx,
             ZERO_REPEAT_SIDE_EFFECTS,
             span.source_callsite(),
-            "function or method calls as the initial value in zero-sized array initializers may cause side effects",
+            "expression with side effects as the initial value in a zero-sized array initializer",
             |diag| {
                 diag.span_suggestion_verbose(
                     span.source_callsite(),

tests/ui/zero_repeat_side_effects.fixed

@@ -77,3 +77,27 @@ fn issue_13110() {
     const LENGTH: usize = LEN!();
     let _data = [f(); LENGTH];
 }
+
+// TODO: consider moving the defintion+impl inside `issue_14681`
+// once https://github.com/rust-lang/rust/issues/146786 is fixed
+#[derive(Clone, Copy)]
+struct S;
+
+impl S {
+    fn new() -> Self {
+        println!("This is a side effect");
+        S
+    }
+}
+
+// should not trigger on non-function calls
+fn issue_14681() {
+    fn foo<T>(_s: &[Option<T>]) {}
+
+    foo(&[Some(0i64); 0]);
+    foo(&[Some(Some(0i64)); 0]);
+    foo(&{ Some(f()); [] as [std::option::Option<i32>; 0] });
+    //~^ zero_repeat_side_effects
+    foo(&{ Some(Some(S::new())); [] as [std::option::Option<std::option::Option<S>>; 0] });
+    //~^ zero_repeat_side_effects
+}

tests/ui/zero_repeat_side_effects.rs

@@ -77,3 +77,27 @@ fn issue_13110() {
     const LENGTH: usize = LEN!();
     let _data = [f(); LENGTH];
 }
+
+// TODO: consider moving the defintion+impl inside `issue_14681`
+// once https://github.com/rust-lang/rust/issues/146786 is fixed
+#[derive(Clone, Copy)]
+struct S;
+
+impl S {
+    fn new() -> Self {
+        println!("This is a side effect");
+        S
+    }
+}
+
+// should not trigger on non-function calls
+fn issue_14681() {
+    fn foo<T>(_s: &[Option<T>]) {}
+
+    foo(&[Some(0i64); 0]);
+    foo(&[Some(Some(0i64)); 0]);
+    foo(&[Some(f()); 0]);
+    //~^ zero_repeat_side_effects
+    foo(&[Some(Some(S::new())); 0]);
+    //~^ zero_repeat_side_effects
+}

tests/ui/zero_repeat_side_effects.stderr

@@ -1,4 +1,4 @@
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:16:5
    |
 LL |     let a = [f(); 0];
@@ -12,7 +12,7 @@ LL -     let a = [f(); 0];
 LL +     f(); let a: [i32; 0] = [];
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:19:5
    |
 LL |     b = [f(); 0];
@@ -24,7 +24,7 @@ LL -     b = [f(); 0];
 LL +     f(); b = [] as [i32; 0];
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:24:5
    |
 LL |     let c = vec![f(); 0];
@@ -36,7 +36,7 @@ LL -     let c = vec![f(); 0];
 LL +     f(); let c: std::vec::Vec<i32> = vec![];
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:27:5
    |
 LL |     d = vec![f(); 0];
@@ -48,7 +48,7 @@ LL -     d = vec![f(); 0];
 LL +     f(); d = vec![] as std::vec::Vec<i32>;
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:31:5
    |
 LL |     let e = [println!("side effect"); 0];
@@ -60,7 +60,7 @@ LL -     let e = [println!("side effect"); 0];
 LL +     println!("side effect"); let e: [(); 0] = [];
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:35:5
    |
 LL |     let g = [{ f() }; 0];
@@ -72,7 +72,7 @@ LL -     let g = [{ f() }; 0];
 LL +     { f() }; let g: [i32; 0] = [];
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:39:10
    |
 LL |     drop(vec![f(); 0]);
@@ -84,7 +84,7 @@ LL -     drop(vec![f(); 0]);
 LL +     drop({ f(); vec![] as std::vec::Vec<i32> });
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:43:5
    |
 LL |     vec![f(); 0];
@@ -96,7 +96,7 @@ LL -     vec![f(); 0];
 LL +     { f(); vec![] as std::vec::Vec<i32> };
    |
 
-error: function or method calls as the initial value in zero-sized array initializers may cause side effects
+error: expression with side effects as the initial value in a zero-sized array initializer
   --> tests/ui/zero_repeat_side_effects.rs:45:5
    |
 LL |     [f(); 0];
@@ -108,5 +108,29 @@ LL -     [f(); 0];
 LL +     { f(); [] as [i32; 0] };
    |
 
-error: aborting due to 9 previous errors
+error: expression with side effects as the initial value in a zero-sized array initializer
+  --> tests/ui/zero_repeat_side_effects.rs:99:10
+   |
+LL |     foo(&[Some(f()); 0]);
+   |          ^^^^^^^^^^^^^^
+   |
+help: consider performing the side effect separately
+   |
+LL -     foo(&[Some(f()); 0]);
+LL +     foo(&{ Some(f()); [] as [std::option::Option<i32>; 0] });
+   |
+
+error: expression with side effects as the initial value in a zero-sized array initializer
+  --> tests/ui/zero_repeat_side_effects.rs:101:10
+   |
+LL |     foo(&[Some(Some(S::new())); 0]);
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider performing the side effect separately
+   |
+LL -     foo(&[Some(Some(S::new())); 0]);
+LL +     foo(&{ Some(Some(S::new())); [] as [std::option::Option<std::option::Option<S>>; 0] });
+   |
+
+error: aborting due to 11 previous errors