clean-up

- move `is_allowed_vec_method` to utils -- shared between `useless_vec`
and `ptr/`
- add another test for non-standard macro brace case
- rm unneeded `allow`s
- rm duplicated tests
- add comments to some tests

Author: ada4a

clippy_lints/src/ptr.rs

@@ -3,7 +3,7 @@ use clippy_utils::res::{MaybeDef, MaybeResPath};
 use clippy_utils::source::SpanRangeExt;
 use clippy_utils::sugg::Sugg;
 use clippy_utils::visitors::contains_unsafe_block;
-use clippy_utils::{get_expr_use_or_unification_node, is_lint_allowed, std_or_core, sym};
+use clippy_utils::{get_expr_use_or_unification_node, is_allowed_vec_method, is_lint_allowed, std_or_core, sym};
 use hir::LifetimeKind;
 use rustc_abi::ExternAbi;
 use rustc_errors::{Applicability, MultiSpan};
@@ -25,8 +25,6 @@ use rustc_trait_selection::infer::InferCtxtExt as _;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
 use std::{fmt, iter};
 
-use crate::useless_vec::is_allowed_vec_method;
-
 declare_clippy_lint! {
     /// ### What it does
     /// This lint checks for function arguments of type `&String`, `&Vec`,

clippy_lints/src/useless_vec.rs

@@ -10,7 +10,7 @@ use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::source::SpanRangeExt;
 use clippy_utils::ty::is_copy;
 use clippy_utils::visitors::for_each_local_use_after_expr;
-use clippy_utils::{get_parent_expr, higher, is_in_test, span_contains_comment, sym};
+use clippy_utils::{get_parent_expr, higher, is_allowed_vec_method, is_in_test, span_contains_comment};
 use rustc_errors::Applicability;
 use rustc_hir::{BorrowKind, Expr, ExprKind, HirId, LetStmt, Mutability, Node, Pat, PatKind};
 use rustc_lint::{LateContext, LateLintPass};
@@ -144,8 +144,9 @@ impl UselessVec {
                 VecToArray::Impossible
             },
             // search for `for _ in vec![...]`
-            Node::Expr(Expr { span, .. })
-                if span.is_desugaring(DesugaringKind::ForLoop) && self.msrv.meets(cx, msrvs::ARRAY_INTO_ITERATOR) =>
+            Node::Expr(expr)
+                if expr.span.is_desugaring(DesugaringKind::ForLoop)
+                    && self.msrv.meets(cx, msrvs::ARRAY_INTO_ITERATOR) =>
             {
                 VecToArray::Possible
             },
@@ -276,9 +277,8 @@ impl SuggestedType {
         assert!(args_span.is_none_or(|s| !s.from_expansion()));
         assert!(len_span.is_none_or(|s| !s.from_expansion()));
 
-        let maybe_args = args_span
-            .map(|sp| sp.get_source_text(cx).expect("spans are always crate-local"))
-            .map_or(String::new(), |x| x.to_owned());
+        let maybe_args = args_span.map(|sp| sp.get_source_text(cx).expect("spans are always crate-local"));
+        let maybe_args = maybe_args.as_deref().unwrap_or_default();
         let maybe_len = len_span
             .map(|sp| sp.get_source_text(cx).expect("spans are always crate-local"))
             .map(|st| format!("; {st}"))
@@ -301,17 +301,6 @@ fn adjusts_to_slice(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
     matches!(cx.typeck_results().expr_ty_adjusted(e).kind(), ty::Ref(_, ty, _) if ty.is_slice())
 }
 
-/// Checks if the given expression is a method call to a `Vec` method
-/// that also exists on slices. If this returns true, it means that
-/// this expression does not actually require a `Vec` and could just work with an array.
-pub fn is_allowed_vec_method(e: &Expr<'_>) -> bool {
-    if let ExprKind::MethodCall(path, _, [], _) = e.kind {
-        matches!(path.ident.name, sym::as_ptr | sym::is_empty | sym::len)
-    } else {
-        false
-    }
-}
-
 fn suggest_type(expr: &Expr<'_>) -> SuggestedType {
     if let ExprKind::AddrOf(BorrowKind::Ref, mutability, _) = expr.kind {
         // `expr` is `&vec![_]`, so suggest `&[_]` (or `&mut[_]` resp.)

clippy_utils/src/lib.rs

@@ -3524,3 +3524,14 @@ pub fn is_expr_async_block(expr: &Expr<'_>) -> bool {
 pub fn can_use_if_let_chains(cx: &LateContext<'_>, msrv: Msrv) -> bool {
     cx.tcx.sess.edition().at_least_rust_2024() && msrv.meets(cx, msrvs::LET_CHAINS)
 }
+
+/// Checks if the given expression is a method call to a `Vec` method
+/// that also exists on slices. If this returns true, it means that
+/// this expression does not actually require a `Vec` and could just work with an array.
+pub fn is_allowed_vec_method(e: &Expr<'_>) -> bool {
+    if let ExprKind::MethodCall(path, _, [], _) = e.kind {
+        matches!(path.ident.name, sym::as_ptr | sym::is_empty | sym::len)
+    } else {
+        false
+    }
+}

tests/ui/useless_vec.fixed

@@ -1,5 +1,4 @@
 #![warn(clippy::useless_vec)]
-#![allow(clippy::nonstandard_macro_braces, clippy::uninlined_format_args, unused)]
 
 use std::rc::Rc;
 
@@ -39,17 +38,14 @@ fn main() {
     on_mut_slice(&mut [1, 2]);
     //~^ useless_vec
 
-    on_slice(&[1, 2]);
-    //~^ useless_vec
-    on_slice(&[1, 2]);
-    on_mut_slice(&mut [1, 2]);
-    //~^ useless_vec
     #[rustfmt::skip]
-    on_slice(&[1, 2]);
-    //~^ useless_vec
-    on_slice(&[1, 2]);
-    on_mut_slice(&mut [1, 2]);
-    //~^ useless_vec
+    #[allow(clippy::nonstandard_macro_braces)] // not an `expect` as it will only lint _before_ the fix
+    {
+        on_slice(&[1, 2]);
+        //~^ useless_vec
+        on_mut_slice(&mut [1, 2]);
+        //~^ useless_vec
+    };
 
     on_slice(&[1; 2]);
     //~^ useless_vec
@@ -75,22 +71,24 @@ fn main() {
     on_vec(&vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
     on_mut_vec(&mut vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
 
-    // Ok
+    // Ok, size of `vec` higher than `too_large_for_stack`
     for a in vec![1; 201] {
-        println!("{:?}", a);
+        println!("{a:?}");
     }
 
     // https://github.com/rust-lang/rust-clippy/issues/2262#issuecomment-783979246
     let _x: i32 = [1, 2, 3].iter().sum();
     //~^ useless_vec
 
-    // Do lint
-    let mut x = [1, 2, 3];
-    //~^ useless_vec
-    x.fill(123);
-    dbg!(x[0]);
-    dbg!(x.len());
-    dbg!(x.iter().sum::<i32>());
+    // Do lint, only used as slice
+    {
+        let mut x = [1, 2, 3];
+        //~^ useless_vec
+        x.fill(123);
+        dbg!(x[0]);
+        dbg!(x.len());
+        dbg!(x.iter().sum::<i32>());
+    }
 
     let _x: &[i32] = &[1, 2, 3];
     //~^ useless_vec

tests/ui/useless_vec.rs

@@ -1,5 +1,4 @@
 #![warn(clippy::useless_vec)]
-#![allow(clippy::nonstandard_macro_braces, clippy::uninlined_format_args, unused)]
 
 use std::rc::Rc;
 
@@ -39,17 +38,14 @@ fn main() {
     on_mut_slice(&mut vec![1, 2]);
     //~^ useless_vec
 
-    on_slice(&vec![1, 2]);
-    //~^ useless_vec
-    on_slice(&[1, 2]);
-    on_mut_slice(&mut vec![1, 2]);
-    //~^ useless_vec
     #[rustfmt::skip]
-    on_slice(&vec!(1, 2));
-    //~^ useless_vec
-    on_slice(&[1, 2]);
-    on_mut_slice(&mut vec![1, 2]);
-    //~^ useless_vec
+    #[allow(clippy::nonstandard_macro_braces)] // not an `expect` as it will only lint _before_ the fix
+    {
+        on_slice(&vec!(1, 2));
+        //~^ useless_vec
+        on_mut_slice(&mut vec!(1, 2));
+        //~^ useless_vec
+    };
 
     on_slice(&vec![1; 2]);
     //~^ useless_vec
@@ -75,22 +71,24 @@ fn main() {
     on_vec(&vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
     on_mut_vec(&mut vec![1; 201]); // Ok, size of `vec` higher than `too_large_for_stack`
 
-    // Ok
+    // Ok, size of `vec` higher than `too_large_for_stack`
     for a in vec![1; 201] {
-        println!("{:?}", a);
+        println!("{a:?}");
     }
 
     // https://github.com/rust-lang/rust-clippy/issues/2262#issuecomment-783979246
     let _x: i32 = vec![1, 2, 3].iter().sum();
     //~^ useless_vec
 
-    // Do lint
-    let mut x = vec![1, 2, 3];
-    //~^ useless_vec
-    x.fill(123);
-    dbg!(x[0]);
-    dbg!(x.len());
-    dbg!(x.iter().sum::<i32>());
+    // Do lint, only used as slice
+    {
+        let mut x = vec![1, 2, 3];
+        //~^ useless_vec
+        x.fill(123);
+        dbg!(x[0]);
+        dbg!(x.len());
+        dbg!(x.iter().sum::<i32>());
+    }
 
     let _x: &[i32] = &vec![1, 2, 3];
     //~^ useless_vec

tests/ui/useless_vec.stderr

@@ -1,5 +1,5 @@
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:30:14
+  --> tests/ui/useless_vec.rs:29:14
    |
 LL |     on_slice(&vec![]);
    |              ^^^^^^^ help: you can use a slice directly: `&[]`
@@ -8,130 +8,118 @@ LL |     on_slice(&vec![]);
    = help: to override `-D warnings` add `#[allow(clippy::useless_vec)]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:33:18
+  --> tests/ui/useless_vec.rs:32:18
    |
 LL |     on_mut_slice(&mut vec![]);
    |                  ^^^^^^^^^^^ help: you can use a slice directly: `&mut []`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:36:14
+  --> tests/ui/useless_vec.rs:35:14
    |
 LL |     on_slice(&vec![1, 2]);
    |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:39:18
+  --> tests/ui/useless_vec.rs:38:18
    |
 LL |     on_mut_slice(&mut vec![1, 2]);
    |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:42:14
+  --> tests/ui/useless_vec.rs:44:18
    |
-LL |     on_slice(&vec![1, 2]);
-   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
-
-error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:45:18
-   |
-LL |     on_mut_slice(&mut vec![1, 2]);
-   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`
+LL |         on_slice(&vec!(1, 2));
+   |                  ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:48:14
+  --> tests/ui/useless_vec.rs:46:22
    |
-LL |     on_slice(&vec!(1, 2));
-   |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
-
-error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:51:18
-   |
-LL |     on_mut_slice(&mut vec![1, 2]);
-   |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`
+LL |         on_mut_slice(&mut vec!(1, 2));
+   |                      ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1, 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:54:14
+  --> tests/ui/useless_vec.rs:50:14
    |
 LL |     on_slice(&vec![1; 2]);
    |              ^^^^^^^^^^^ help: you can use a slice directly: `&[1; 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:57:18
+  --> tests/ui/useless_vec.rs:53:18
    |
 LL |     on_mut_slice(&mut vec![1; 2]);
    |                  ^^^^^^^^^^^^^^^ help: you can use a slice directly: `&mut [1; 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:84:19
+  --> tests/ui/useless_vec.rs:80:19
    |
 LL |     let _x: i32 = vec![1, 2, 3].iter().sum();
    |                   ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:88:17
+  --> tests/ui/useless_vec.rs:85:21
    |
-LL |     let mut x = vec![1, 2, 3];
-   |                 ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`
+LL |         let mut x = vec![1, 2, 3];
+   |                     ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:95:22
+  --> tests/ui/useless_vec.rs:93:22
    |
 LL |     let _x: &[i32] = &vec![1, 2, 3];
    |                      ^^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2, 3]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:98:14
+  --> tests/ui/useless_vec.rs:96:14
    |
 LL |     for _ in vec![1, 2, 3] {}
    |              ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:138:20
+  --> tests/ui/useless_vec.rs:136:20
    |
 LL |     for _string in vec![repro!(true), repro!(null)] {
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[repro!(true), repro!(null)]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:156:18
+  --> tests/ui/useless_vec.rs:154:18
    |
 LL |     in_macro!(1, vec![1, 2], vec![1; 2]);
    |                  ^^^^^^^^^^ help: you can use an array directly: `[1, 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:156:30
+  --> tests/ui/useless_vec.rs:154:30
    |
 LL |     in_macro!(1, vec![1, 2], vec![1; 2]);
    |                              ^^^^^^^^^^ help: you can use an array directly: `[1; 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:177:14
+  --> tests/ui/useless_vec.rs:175:14
    |
 LL |     for a in vec![1, 2, 3] {
    |              ^^^^^^^^^^^^^ help: you can use an array directly: `[1, 2, 3]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:182:14
+  --> tests/ui/useless_vec.rs:180:14
    |
 LL |     for a in vec![String::new(), String::new()] {
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[String::new(), String::new()]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:215:33
+  --> tests/ui/useless_vec.rs:213:33
    |
 LL |     this_macro_doesnt_need_vec!(vec![1]);
    |                                 ^^^^^^^ help: you can use an array directly: `[1]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:242:14
+  --> tests/ui/useless_vec.rs:240:14
    |
 LL |     for a in &(vec![1, 2]) {}
    |              ^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`
 
 error: useless use of `vec!`
-  --> tests/ui/useless_vec.rs:250:13
+  --> tests/ui/useless_vec.rs:248:13
    |
 LL |     let v = &vec![];
    |             ^^^^^^^ help: you can use a slice directly: `&[]`
 
-error: aborting due to 22 previous errors
+error: aborting due to 20 previous errors
 

tests/ui/useless_vec_unfixable.rs

@@ -1,5 +1,4 @@
 //@no-rustfix: no suggestions
-
 #![warn(clippy::useless_vec)]
 
 // Regression test for <https://github.com/rust-lang/rust-clippy/issues/13692>.

tests/ui/useless_vec_unfixable.stderr

@@ -1,5 +1,5 @@
 error: useless use of `vec!`
-  --> tests/ui/useless_vec_unfixable.rs:8:26
+  --> tests/ui/useless_vec_unfixable.rs:7:26
    |
 LL |       let _some_variable = vec![
    |  __________________________^