Fix: zero_repeat_side_effects misses curlies (#15853)

Closes #15824
Closes #15825

changelog: [`zero_repeat_side_effects`] fix missing curlies

Author: blyxyas

clippy_lints/src/zero_repeat_side_effects.rs

@@ -4,10 +4,11 @@ use clippy_utils::source::{snippet, snippet_indent};
 use rustc_ast::LitKind;
 use rustc_data_structures::packed::Pu128;
 use rustc_errors::Applicability;
-use rustc_hir::{ConstArgKind, ExprKind, Node};
+use rustc_hir::{ConstArgKind, Expr, ExprKind, LetStmt, LocalSource, Node};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::IsSuggestable;
+use rustc_middle::ty::{IsSuggestable, Ty};
 use rustc_session::declare_lint_pass;
+use rustc_span::Span;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -44,7 +45,7 @@ declare_clippy_lint! {
 declare_lint_pass!(ZeroRepeatSideEffects => [ZERO_REPEAT_SIDE_EFFECTS]);
 
 impl LateLintPass<'_> for ZeroRepeatSideEffects {
-    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &rustc_hir::Expr<'_>) {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
         if let Some(args) = VecArgs::hir(cx, expr)
             && let VecArgs::Repeat(inner_expr, len) = args
             && let ExprKind::Lit(l) = len.kind
@@ -69,7 +70,7 @@ impl LateLintPass<'_> for ZeroRepeatSideEffects {
     }
 }
 
-fn inner_check(cx: &LateContext<'_>, expr: &'_ rustc_hir::Expr<'_>, inner_expr: &'_ rustc_hir::Expr<'_>, is_vec: bool) {
+fn inner_check(cx: &LateContext<'_>, expr: &'_ Expr<'_>, inner_expr: &'_ Expr<'_>, is_vec: bool) {
     // check if expr is a call or has a call inside it
     if inner_expr.can_have_side_effects() {
         let parent_hir_node = cx.tcx.parent_hir_node(expr.hir_id);
@@ -81,19 +82,22 @@ fn inner_check(cx: &LateContext<'_>, expr: &'_ rustc_hir::Expr<'_>, inner_expr:
         let vec = if is_vec { "vec!" } else { "" };
 
         let (span, sugg) = match parent_hir_node {
-            Node::LetStmt(l) => (
-                l.span,
-                format!(
-                    "{inner_expr};\n{indent}let {var_name}: {return_type} = {vec}[];",
-                    var_name = snippet(cx, l.pat.span.source_callsite(), "..")
-                ),
-            ),
+            Node::LetStmt(l)
+                if matches!(l.source, LocalSource::AssignDesugar(_))
+                    && let mut parent_iter = cx.tcx.hir_parent_iter(l.hir_id)
+                    && let Some((_, Node::Stmt(_))) = parent_iter.next()
+                    && let Some((_, Node::Block(_))) = parent_iter.next()
+                    && let Some((_, Node::Expr(x))) = parent_iter.next() =>
+            {
+                (
+                    x.span,
+                    assign_expr_suggestion(cx, x, l.pat.span, &inner_expr, return_type, vec),
+                )
+            },
+            Node::LetStmt(l) => (l.span, let_stmt_suggestion(cx, l, &inner_expr, return_type, vec)),
             Node::Expr(x) if let ExprKind::Assign(l, _, _) = x.kind => (
                 x.span,
-                format!(
-                    "{inner_expr};\n{indent}{var_name} = {vec}[] as {return_type}",
-                    var_name = snippet(cx, l.span.source_callsite(), "..")
-                ),
+                assign_expr_suggestion(cx, x, l.span, &inner_expr, return_type, vec),
             ),
             // NOTE: don't use the stmt span to avoid touching the trailing semicolon
             Node::Stmt(_) => (expr.span, format!("{inner_expr};\n{indent}{vec}[] as {return_type}")),
@@ -131,3 +135,41 @@ fn inner_check(cx: &LateContext<'_>, expr: &'_ rustc_hir::Expr<'_>, inner_expr:
         );
     }
 }
+
+fn let_stmt_suggestion(
+    cx: &LateContext<'_>,
+    let_stmt: &LetStmt<'_>,
+    inner_expr: &str,
+    return_type: Ty<'_>,
+    vec_str: &str,
+) -> String {
+    let indent = snippet_indent(cx, let_stmt.span).unwrap_or_default();
+    format!(
+        "{inner_expr};\n{}let {var_name}: {return_type} = {vec_str}[];",
+        indent,
+        var_name = snippet(cx, let_stmt.pat.span.source_callsite(), "..")
+    )
+}
+
+fn assign_expr_suggestion(
+    cx: &LateContext<'_>,
+    outer_expr: &Expr<'_>,
+    assign_expr_span: Span,
+    inner_expr: &str,
+    return_type: Ty<'_>,
+    vec_str: &str,
+) -> String {
+    let mut parent_hir_node = cx.tcx.parent_hir_node(outer_expr.hir_id);
+    if let Node::Stmt(stmt) = parent_hir_node {
+        parent_hir_node = cx.tcx.parent_hir_node(stmt.hir_id);
+    }
+    let needs_curly = !matches!(parent_hir_node, Node::Block(_));
+
+    let indent = snippet_indent(cx, outer_expr.span).unwrap_or_default();
+    let var_name = snippet(cx, assign_expr_span.source_callsite(), "..");
+    if needs_curly {
+        format!("{{\n    {indent}{inner_expr};\n    {indent}{var_name} = {vec_str}[] as {return_type}\n{indent}}}",)
+    } else {
+        format!("{inner_expr};\n{indent}{var_name} = {vec_str}[] as {return_type}")
+    }
+}

tests/ui/zero_repeat_side_effects.fixed

@@ -1,6 +1,11 @@
 #![warn(clippy::zero_repeat_side_effects)]
-#![expect(clippy::unnecessary_operation, clippy::useless_vec, clippy::needless_late_init)]
-#![allow(clippy::no_effect)] // only fires _after_ the fix
+#![allow(
+    clippy::unnecessary_operation,
+    clippy::useless_vec,
+    clippy::needless_late_init,
+    clippy::single_match,
+    clippy::no_effect // only fires _after_ the fix
+)]
 
 fn f() -> i32 {
     println!("side effect");
@@ -119,3 +124,26 @@ fn issue_14681() {
     });
     //~^ zero_repeat_side_effects
 }
+
+fn issue_15824() {
+    fn f() {}
+
+    match 0 {
+        0 => {
+            f();
+            _ = [] as [(); 0]
+        },
+        //~^ zero_repeat_side_effects
+        _ => {},
+    }
+
+    let mut a = [(); 0];
+    match 0 {
+        0 => {
+            f();
+            a = [] as [(); 0]
+        },
+        //~^ zero_repeat_side_effects
+        _ => {},
+    }
+}

tests/ui/zero_repeat_side_effects.rs

@@ -1,6 +1,11 @@
 #![warn(clippy::zero_repeat_side_effects)]
-#![expect(clippy::unnecessary_operation, clippy::useless_vec, clippy::needless_late_init)]
-#![allow(clippy::no_effect)] // only fires _after_ the fix
+#![allow(
+    clippy::unnecessary_operation,
+    clippy::useless_vec,
+    clippy::needless_late_init,
+    clippy::single_match,
+    clippy::no_effect // only fires _after_ the fix
+)]
 
 fn f() -> i32 {
     println!("side effect");
@@ -102,3 +107,20 @@ fn issue_14681() {
     foo(&[Some(Some(S::new())); 0]);
     //~^ zero_repeat_side_effects
 }
+
+fn issue_15824() {
+    fn f() {}
+
+    match 0 {
+        0 => _ = [f(); 0],
+        //~^ zero_repeat_side_effects
+        _ => {},
+    }
+
+    let mut a = [(); 0];
+    match 0 {
+        0 => a = [f(); 0],
+        //~^ zero_repeat_side_effects
+        _ => {},
+    }
+}

tests/ui/zero_repeat_side_effects.stderr

@@ -1,5 +1,5 @@
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:17:5
+  --> tests/ui/zero_repeat_side_effects.rs:22:5
    |
 LL |     let a = [f(); 0];
    |     ^^^^^^^^^^^^^^^^^
@@ -13,7 +13,7 @@ LL +     let a: [i32; 0] = [];
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:20:5
+  --> tests/ui/zero_repeat_side_effects.rs:25:5
    |
 LL |     b = [f(); 0];
    |     ^^^^^^^^^^^^
@@ -25,7 +25,7 @@ LL ~     b = [] as [i32; 0];
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:25:5
+  --> tests/ui/zero_repeat_side_effects.rs:30:5
    |
 LL |     let c = vec![f(); 0];
    |     ^^^^^^^^^^^^^^^^^^^^^
@@ -37,7 +37,7 @@ LL +     let c: std::vec::Vec<i32> = vec![];
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:28:5
+  --> tests/ui/zero_repeat_side_effects.rs:33:5
    |
 LL |     d = vec![f(); 0];
    |     ^^^^^^^^^^^^^^^^
@@ -49,7 +49,7 @@ LL ~     d = vec![] as std::vec::Vec<i32>;
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:32:5
+  --> tests/ui/zero_repeat_side_effects.rs:37:5
    |
 LL |     let e = [println!("side effect"); 0];
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -61,7 +61,7 @@ LL +     let e: [(); 0] = [];
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:36:5
+  --> tests/ui/zero_repeat_side_effects.rs:41:5
    |
 LL |     let g = [{ f() }; 0];
    |     ^^^^^^^^^^^^^^^^^^^^^
@@ -73,7 +73,7 @@ LL +     let g: [i32; 0] = [];
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:40:10
+  --> tests/ui/zero_repeat_side_effects.rs:45:10
    |
 LL |     drop(vec![f(); 0]);
    |          ^^^^^^^^^^^^
@@ -87,7 +87,7 @@ LL ~     });
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:44:5
+  --> tests/ui/zero_repeat_side_effects.rs:49:5
    |
 LL |     vec![f(); 0];
    |     ^^^^^^^^^^^^
@@ -99,7 +99,7 @@ LL ~     vec![] as std::vec::Vec<i32>;
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:46:5
+  --> tests/ui/zero_repeat_side_effects.rs:51:5
    |
 LL |     [f(); 0];
    |     ^^^^^^^^
@@ -111,7 +111,7 @@ LL ~     [] as [i32; 0];
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:100:10
+  --> tests/ui/zero_repeat_side_effects.rs:105:10
    |
 LL |     foo(&[Some(f()); 0]);
    |          ^^^^^^^^^^^^^^
@@ -125,7 +125,7 @@ LL ~     });
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:102:10
+  --> tests/ui/zero_repeat_side_effects.rs:107:10
    |
 LL |     foo(&[Some(Some(S::new())); 0]);
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -138,5 +138,33 @@ LL +         [] as [std::option::Option<std::option::Option<S>>; 0]
 LL ~     });
    |
 
-error: aborting due to 11 previous errors
+error: expression with side effects as the initial value in a zero-sized array initializer
+  --> tests/ui/zero_repeat_side_effects.rs:115:14
+   |
+LL |         0 => _ = [f(); 0],
+   |              ^^^^^^^^^^^^
+   |
+help: consider performing the side effect separately
+   |
+LL ~         0 => {
+LL +             f();
+LL +             _ = [] as [(); 0]
+LL ~         },
+   |
+
+error: expression with side effects as the initial value in a zero-sized array initializer
+  --> tests/ui/zero_repeat_side_effects.rs:122:14
+   |
+LL |         0 => a = [f(); 0],
+   |              ^^^^^^^^^^^^
+   |
+help: consider performing the side effect separately
+   |
+LL ~         0 => {
+LL +             f();
+LL +             a = [] as [(); 0]
+LL ~         },
+   |
+
+error: aborting due to 13 previous errors