feat(zero_repeat_side_effects): don't suggest unnecessary braces around stmts (rust-lang#15826)

changelog: [`(zero_repeat_side_effects`]: don't suggest unnecessary
braces around stmts

r? @samueltardieu

Author: samueltardieu

clippy_lints/src/zero_repeat_side_effects.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::higher::VecArgs;
-use clippy_utils::source::snippet;
+use clippy_utils::source::{snippet, snippet_indent};
 use rustc_ast::LitKind;
 use rustc_data_structures::packed::Pu128;
 use rustc_errors::Applicability;
@@ -77,24 +77,36 @@ fn inner_check(cx: &LateContext<'_>, expr: &'_ rustc_hir::Expr<'_>, inner_expr:
         let return_type = cx.typeck_results().expr_ty(expr);
 
         let inner_expr = snippet(cx, inner_expr.span.source_callsite(), "..");
+        let indent = snippet_indent(cx, expr.span).unwrap_or_default();
         let vec = if is_vec { "vec!" } else { "" };
 
         let (span, sugg) = match parent_hir_node {
             Node::LetStmt(l) => (
                 l.span,
                 format!(
-                    "{inner_expr}; let {var_name}: {return_type} = {vec}[];",
+                    "{inner_expr};\n{indent}let {var_name}: {return_type} = {vec}[];",
                     var_name = snippet(cx, l.pat.span.source_callsite(), "..")
                 ),
             ),
             Node::Expr(x) if let ExprKind::Assign(l, _, _) = x.kind => (
                 x.span,
                 format!(
-                    "{inner_expr}; {var_name} = {vec}[] as {return_type}",
+                    "{inner_expr};\n{indent}{var_name} = {vec}[] as {return_type}",
                     var_name = snippet(cx, l.span.source_callsite(), "..")
                 ),
             ),
-            _ => (expr.span, format!("{{ {inner_expr}; {vec}[] as {return_type} }}")),
+            // 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}")),
+            _ => (
+                expr.span,
+                format!(
+                    "\
+{{
+{indent}    {inner_expr};
+{indent}    {vec}[] as {return_type}
+{indent}}}"
+                ),
+            ),
         };
         let span = span.source_callsite();
         span_lint_and_then(

tests/ui/zero_repeat_side_effects.fixed

@@ -1,5 +1,6 @@
 #![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
 
 fn f() -> i32 {
     println!("side effect");
@@ -13,36 +14,47 @@ fn main() {
     // should trigger
 
     // on arrays
-    f(); let a: [i32; 0] = [];
+    f();
+    let a: [i32; 0] = [];
     //~^ zero_repeat_side_effects
     let mut b;
-    f(); b = [] as [i32; 0];
+    f();
+    b = [] as [i32; 0];
     //~^ zero_repeat_side_effects
 
     // on vecs
     // vecs dont support inferring value of consts
-    f(); let c: std::vec::Vec<i32> = vec![];
+    f();
+    let c: std::vec::Vec<i32> = vec![];
     //~^ zero_repeat_side_effects
     let d;
-    f(); d = vec![] as std::vec::Vec<i32>;
+    f();
+    d = vec![] as std::vec::Vec<i32>;
     //~^ zero_repeat_side_effects
 
     // for macros
-    println!("side effect"); let e: [(); 0] = [];
+    println!("side effect");
+    let e: [(); 0] = [];
     //~^ zero_repeat_side_effects
 
     // for nested calls
-    { f() }; let g: [i32; 0] = [];
+    { f() };
+    let g: [i32; 0] = [];
     //~^ zero_repeat_side_effects
 
     // as function param
-    drop({ f(); vec![] as std::vec::Vec<i32> });
+    drop({
+        f();
+        vec![] as std::vec::Vec<i32>
+    });
     //~^ zero_repeat_side_effects
 
     // when singled out/not part of assignment/local
-    { f(); vec![] as std::vec::Vec<i32> };
+    f();
+    vec![] as std::vec::Vec<i32>;
     //~^ zero_repeat_side_effects
-    { f(); [] as [i32; 0] };
+    f();
+    [] as [i32; 0];
     //~^ zero_repeat_side_effects
 
     // should not trigger
@@ -96,8 +108,14 @@ fn issue_14681() {
 
     foo(&[Some(0i64); 0]);
     foo(&[Some(Some(0i64)); 0]);
-    foo(&{ Some(f()); [] as [std::option::Option<i32>; 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] });
+    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

@@ -1,5 +1,6 @@
 #![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
 
 fn f() -> i32 {
     println!("side effect");

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:16:5
+  --> tests/ui/zero_repeat_side_effects.rs:17:5
    |
 LL |     let a = [f(); 0];
    |     ^^^^^^^^^^^^^^^^^
@@ -8,128 +8,134 @@ LL |     let a = [f(); 0];
    = help: to override `-D warnings` add `#[allow(clippy::zero_repeat_side_effects)]`
 help: consider performing the side effect separately
    |
-LL -     let a = [f(); 0];
-LL +     f(); let a: [i32; 0] = [];
+LL ~     f();
+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:19:5
+  --> tests/ui/zero_repeat_side_effects.rs:20:5
    |
 LL |     b = [f(); 0];
    |     ^^^^^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     b = [f(); 0];
-LL +     f(); b = [] as [i32; 0];
+LL ~     f();
+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:24:5
+  --> tests/ui/zero_repeat_side_effects.rs:25:5
    |
 LL |     let c = vec![f(); 0];
    |     ^^^^^^^^^^^^^^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     let c = vec![f(); 0];
-LL +     f(); let c: std::vec::Vec<i32> = vec![];
+LL ~     f();
+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:27:5
+  --> tests/ui/zero_repeat_side_effects.rs:28:5
    |
 LL |     d = vec![f(); 0];
    |     ^^^^^^^^^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     d = vec![f(); 0];
-LL +     f(); d = vec![] as std::vec::Vec<i32>;
+LL ~     f();
+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:31:5
+  --> tests/ui/zero_repeat_side_effects.rs:32:5
    |
 LL |     let e = [println!("side effect"); 0];
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     let e = [println!("side effect"); 0];
-LL +     println!("side effect"); let e: [(); 0] = [];
+LL ~     println!("side effect");
+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:35:5
+  --> tests/ui/zero_repeat_side_effects.rs:36:5
    |
 LL |     let g = [{ f() }; 0];
    |     ^^^^^^^^^^^^^^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     let g = [{ f() }; 0];
-LL +     { f() }; let g: [i32; 0] = [];
+LL ~     { f() };
+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:39:10
+  --> tests/ui/zero_repeat_side_effects.rs:40:10
    |
 LL |     drop(vec![f(); 0]);
    |          ^^^^^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     drop(vec![f(); 0]);
-LL +     drop({ f(); vec![] as std::vec::Vec<i32> });
+LL ~     drop({
+LL +         f();
+LL +         vec![] as std::vec::Vec<i32>
+LL ~     });
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:43:5
+  --> tests/ui/zero_repeat_side_effects.rs:44:5
    |
 LL |     vec![f(); 0];
    |     ^^^^^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     vec![f(); 0];
-LL +     { f(); vec![] as std::vec::Vec<i32> };
+LL ~     f();
+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:45:5
+  --> tests/ui/zero_repeat_side_effects.rs:46:5
    |
 LL |     [f(); 0];
    |     ^^^^^^^^
    |
 help: consider performing the side effect separately
    |
-LL -     [f(); 0];
-LL +     { f(); [] as [i32; 0] };
+LL ~     f();
+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:99:10
+  --> tests/ui/zero_repeat_side_effects.rs:100:10
    |
 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] });
+LL ~     foo(&{
+LL +         Some(f());
+LL +         [] as [std::option::Option<i32>; 0]
+LL ~     });
    |
 
 error: expression with side effects as the initial value in a zero-sized array initializer
-  --> tests/ui/zero_repeat_side_effects.rs:101:10
+  --> tests/ui/zero_repeat_side_effects.rs:102:10
    |
 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] });
+LL ~     foo(&{
+LL +         Some(Some(S::new()));
+LL +         [] as [std::option::Option<std::option::Option<S>>; 0]
+LL ~     });
    |
 
 error: aborting due to 11 previous errors

tests/ui/zero_repeat_side_effects_never_pattern.fixed

@@ -4,6 +4,7 @@
 
 fn issue_14998() {
     // nameable type thanks to `never_type` being enabled, suggest
-    panic!(); let _data: [!; 0] = [];
+    panic!();
+    let _data: [!; 0] = [];
     //~^ zero_repeat_side_effects
 }

tests/ui/zero_repeat_side_effects_never_pattern.stderr

@@ -8,8 +8,8 @@ LL |     let _data = [panic!(); 0];
    = help: to override `-D warnings` add `#[allow(clippy::zero_repeat_side_effects)]`
 help: consider performing the side effect separately
    |
-LL -     let _data = [panic!(); 0];
-LL +     panic!(); let _data: [!; 0] = [];
+LL ~     panic!();
+LL +     let _data: [!; 0] = [];
    |
 
 error: aborting due to 1 previous error