needless_pass_by_value: make verbose suggestion

samueltardieu · samueltardieu · commit 417d4e6210d5 · 2025-03-12T13:50:04.000+01:00
This reduces the number of snippet manipulations, and shows the new
reference in context.
diff --git a/clippy_lints/src/needless_pass_by_value.rs b/clippy_lints/src/needless_pass_by_value.rs
@@ -279,13 +279,10 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                         }
                     }
 
-                    let inner_input = peel_hir_ty_options(cx, input);
-                    let before_span = input.span.until(inner_input.span);
-                    let after_span = before_span.shrink_to_hi().to(input.span.shrink_to_hi());
-                    diag.span_suggestion(
-                        input.span,
+                    diag.span_suggestion_verbose(
+                        peel_hir_ty_options(cx, input).span.shrink_to_lo(),
                         "consider taking a reference instead",
-                        format!("{}&{}", snippet(cx, before_span, "_"), snippet(cx, after_span, "_")),
+                        '&',
                         Applicability::MaybeIncorrect,
                     );
                 };
diff --git a/tests/ui/crashes/needless_pass_by_value-w-late-bound.stderr b/tests/ui/crashes/needless_pass_by_value-w-late-bound.stderr
@@ -2,7 +2,7 @@ error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/crashes/needless_pass_by_value-w-late-bound.rs:7:12
    |
 LL | fn test(x: Foo<'_>) {}
-   |            ^^^^^^^ help: consider taking a reference instead: `&Foo<'_>`
+   |            ^^^^^^^
    |
 help: or consider marking this type as `Copy`
   --> tests/ui/crashes/needless_pass_by_value-w-late-bound.rs:5:1
@@ -11,6 +11,10 @@ LL | struct Foo<'a>(&'a [(); 100]);
    | ^^^^^^^^^^^^^^
    = note: `-D clippy::needless-pass-by-value` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::needless_pass_by_value)]`
+help: consider taking a reference instead
+   |
+LL | fn test(x: &Foo<'_>) {}
+   |            +
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/needless_pass_by_value.stderr b/tests/ui/needless_pass_by_value.stderr
@@ -17,43 +17,78 @@ error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:35:22
    |
 LL | fn bar(x: String, y: Wrapper) {
-   |                      ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
+   |                      ^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn bar(x: String, y: &Wrapper) {
+   |                      +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:44:71
    |
 LL | fn test_borrow_trait<T: Borrow<str>, U: AsRef<str>, V>(t: T, u: U, v: V) {
-   |                                                                       ^ help: consider taking a reference instead: `&V`
+   |                                                                       ^
+   |
+help: consider taking a reference instead
+   |
+LL | fn test_borrow_trait<T: Borrow<str>, U: AsRef<str>, V>(t: T, u: U, v: &V) {
+   |                                                                       +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:58:18
    |
 LL | fn test_match(x: Option<Option<String>>, y: Option<Option<String>>) {
-   |                  ^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `Option<Option<&String>>`
+   |                  ^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn test_match(x: Option<Option<&String>>, y: Option<Option<String>>) {
+   |                                +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:73:24
    |
 LL | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
-   |                        ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
+   |                        ^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn test_destructure(x: &Wrapper, y: Wrapper, z: Wrapper) {
+   |                        +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:73:36
    |
 LL | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
-   |                                    ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
+   |                                    ^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn test_destructure(x: Wrapper, y: &Wrapper, z: Wrapper) {
+   |                                    +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:92:49
    |
 LL | fn test_blanket_ref<T: Foo, S: Serialize>(vals: T, serializable: S) {}
-   |                                                 ^ help: consider taking a reference instead: `&T`
+   |                                                 ^
+   |
+help: consider taking a reference instead
+   |
+LL | fn test_blanket_ref<T: Foo, S: Serialize>(vals: &T, serializable: S) {}
+   |                                                 +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:95:18
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
-   |                  ^^^^^^ help: consider taking a reference instead: `&String`
+   |                  ^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn issue_2114(s: &String, t: String, u: Vec<i32>, v: Vec<i32>) {
+   |                  +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:95:29
@@ -76,7 +111,12 @@ error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:95:40
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
-   |                                        ^^^^^^^^ help: consider taking a reference instead: `&Vec<i32>`
+   |                                        ^^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn issue_2114(s: String, t: String, u: &Vec<i32>, v: Vec<i32>) {
+   |                                        +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:95:53
@@ -105,109 +145,175 @@ error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:115:12
    |
 LL |         t: String,
-   |            ^^^^^^ help: consider taking a reference instead: `&String`
+   |            ^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL |         t: &String,
+   |            +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:125:23
    |
 LL |     fn baz(&self, uu: U, ss: Self) {}
-   |                       ^ help: consider taking a reference instead: `&U`
+   |                       ^
+   |
+help: consider taking a reference instead
+   |
+LL |     fn baz(&self, uu: &U, ss: Self) {}
+   |                       +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:125:30
    |
 LL |     fn baz(&self, uu: U, ss: Self) {}
-   |                              ^^^^ help: consider taking a reference instead: `&Self`
+   |                              ^^^^
+   |
+help: consider taking a reference instead
+   |
+LL |     fn baz(&self, uu: U, ss: &Self) {}
+   |                              +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:149:24
    |
 LL | fn bar_copy(x: u32, y: CopyWrapper) {
-   |                        ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
+   |                        ^^^^^^^^^^^
    |
 help: or consider marking this type as `Copy`
   --> tests/ui/needless_pass_by_value.rs:147:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^
+help: consider taking a reference instead
+   |
+LL | fn bar_copy(x: u32, y: &CopyWrapper) {
+   |                        +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:157:29
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
-   |                             ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
+   |                             ^^^^^^^^^^^
    |
 help: or consider marking this type as `Copy`
   --> tests/ui/needless_pass_by_value.rs:147:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^
+help: consider taking a reference instead
+   |
+LL | fn test_destructure_copy(x: &CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
+   |                             +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:157:45
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
-   |                                             ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
+   |                                             ^^^^^^^^^^^
    |
 help: or consider marking this type as `Copy`
   --> tests/ui/needless_pass_by_value.rs:147:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^
+help: consider taking a reference instead
+   |
+LL | fn test_destructure_copy(x: CopyWrapper, y: &CopyWrapper, z: CopyWrapper) {
+   |                                             +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:157:61
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
-   |                                                             ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
+   |                                                             ^^^^^^^^^^^
    |
 help: or consider marking this type as `Copy`
   --> tests/ui/needless_pass_by_value.rs:147:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^
+help: consider taking a reference instead
+   |
+LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: &CopyWrapper) {
+   |                                                             +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:173:40
    |
 LL | fn some_fun<'b, S: Bar<'b, ()>>(items: S) {}
-   |                                        ^ help: consider taking a reference instead: `&S`
+   |                                        ^
+   |
+help: consider taking a reference instead
+   |
+LL | fn some_fun<'b, S: Bar<'b, ()>>(items: &S) {}
+   |                                        +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:179:20
    |
 LL | fn more_fun(items: impl Club<'static, i32>) {}
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&impl Club<'static, i32>`
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn more_fun(items: &impl Club<'static, i32>) {}
+   |                    +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:194:24
    |
 LL | fn option_inner_ref(x: Option<String>) {
-   |                        ^^^^^^^^^^^^^^ help: consider taking a reference instead: `Option<&String>`
+   |                        ^^^^^^^^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn option_inner_ref(x: Option<&String>) {
+   |                               +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:204:27
    |
 LL | fn non_standard_option(x: non_standard::Option<String>) {
-   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&non_standard::Option<String>`
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn non_standard_option(x: &non_standard::Option<String>) {
+   |                           +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:209:22
    |
 LL | fn option_by_name(x: Option<std::option::Option<core::option::Option<non_standard::Option<String>>>>) {
-   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `Option<std::option::Option<core::option::Option<&non_standard::Option<String>>>>`
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn option_by_name(x: Option<std::option::Option<core::option::Option<&non_standard::Option<String>>>>) {
+   |                                                                      +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:216:18
    |
 LL | fn non_option(x: OptStr) {
-   |                  ^^^^^^ help: consider taking a reference instead: `&OptStr`
+   |                  ^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn non_option(x: &OptStr) {
+   |                  +
 
 error: this argument is passed by value, but not consumed in the function body
   --> tests/ui/needless_pass_by_value.rs:223:25
    |
 LL | fn non_option_either(x: Opt<String>) {
-   |                         ^^^^^^^^^^^ help: consider taking a reference instead: `&Opt<String>`
+   |                         ^^^^^^^^^^^
+   |
+help: consider taking a reference instead
+   |
+LL | fn non_option_either(x: &Opt<String>) {
+   |                         +
 
 error: aborting due to 27 previous errors
 
