Tweak borrow suggestion

compiler/rustc_hir_typeck/src/demand.rs

@@ -1334,52 +1334,55 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         ));
                     }
 
-                    if let Ok(src) = sm.span_to_snippet(sugg_sp) {
-                        let needs_parens = match expr.kind {
-                            // parenthesize if needed (Issue #46756)
-                            hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
-                            // parenthesize borrows of range literals (Issue #54505)
-                            _ if is_range_literal(expr) => true,
-                            _ => false,
-                        };
-
-                        if let Some(sugg) = self.can_use_as_ref(expr) {
-                            return Some((
-                                sugg.0,
-                                sugg.1.to_string(),
-                                sugg.2,
-                                Applicability::MachineApplicable,
-                                false,
-                                false,
-                            ));
-                        }
-
-                        let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
-                            Some(ident) => format!("{ident}: "),
-                            None => String::new(),
-                        };
-
-                        if let Some(hir::Node::Expr(hir::Expr {
-                            kind: hir::ExprKind::Assign(..),
-                            ..
-                        })) = self.tcx.hir().find_parent(expr.hir_id)
-                        {
-                            if mutability.is_mut() {
-                                // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
-                                return None;
-                            }
-                        }
+                    let needs_parens = match expr.kind {
+                        // parenthesize if needed (Issue #46756)
+                        hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true,
+                        // parenthesize borrows of range literals (Issue #54505)
+                        _ if is_range_literal(expr) => true,
+                        _ => false,
+                    };
 
-                        let sugg_expr = if needs_parens { format!("({src})") } else { src };
+                    if let Some(sugg) = self.can_use_as_ref(expr) {
                         return Some((
-                            sp,
-                            format!("consider {}borrowing here", mutability.mutably_str()),
-                            format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
+                            sugg.0,
+                            sugg.1.to_string(),
+                            sugg.2,
                             Applicability::MachineApplicable,
                             false,
                             false,
                         ));
                     }
+
+                    let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) {
+                        Some(ident) => format!("{ident}: "),
+                        None => String::new(),
+                    };
+
+                    if let Some(hir::Node::Expr(hir::Expr {
+                        kind: hir::ExprKind::Assign(..),
+                        ..
+                    })) = self.tcx.hir().find_parent(expr.hir_id)
+                    {
+                        if mutability.is_mut() {
+                            // Suppressing this diagnostic, we'll properly print it in `check_expr_assign`
+                            return None;
+                        }
+                    }
+
+                    let (sp, sugg_expr, verbose) = if needs_parens {
+                        let src = sm.span_to_snippet(sugg_sp).ok()?;
+                        (sp, format!("({src})"), false)
+                    } else {
+                        (sp.shrink_to_lo(), "".to_string(), true)
+                    };
+                    return Some((
+                        sp,
+                        format!("consider {}borrowing here", mutability.mutably_str()),
+                        format!("{prefix}{}{sugg_expr}", mutability.ref_prefix_str()),
+                        Applicability::MachineApplicable,
+                        verbose,
+                        false,
+                    ));
                 }
             }
             (

tests/ui/argument-suggestions/issue-97484.stderr

@@ -16,7 +16,7 @@ LL | fn foo(a: &A, d: D, e: &E, g: G) {}
 help: consider borrowing here
    |
 LL |     foo(&&A, B, C, D, &E, F, G);
-   |                       ~~
+   |                       +
 help: remove the extra arguments
    |
 LL -     foo(&&A, B, C, D, E, F, G);

tests/ui/async-await/issues/issue-102206.stderr

@@ -2,14 +2,16 @@ error[E0308]: mismatched types
   --> $DIR/issue-102206.rs:6:27
    |
 LL |     std::mem::size_of_val(foo());
-   |     --------------------- ^^^^^
-   |     |                     |
-   |     |                     expected `&_`, found future
-   |     |                     help: consider borrowing here: `&foo()`
+   |     --------------------- ^^^^^ expected `&_`, found future
+   |     |
    |     arguments to this function are incorrect
    |
 note: function defined here
   --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
+help: consider borrowing here
+   |
+LL |     std::mem::size_of_val(&foo());
+   |                           +
 
 error: aborting due to previous error
 

tests/ui/coercion/coercion-slice.stderr

@@ -2,11 +2,14 @@ error[E0308]: mismatched types
   --> $DIR/coercion-slice.rs:4:21
    |
 LL |     let _: &[i32] = [0];
-   |            ------   ^^^
-   |            |        |
-   |            |        expected `&[i32]`, found `[{integer}; 1]`
-   |            |        help: consider borrowing here: `&[0]`
+   |            ------   ^^^ expected `&[i32]`, found `[{integer}; 1]`
+   |            |
    |            expected due to this
+   |
+help: consider borrowing here
+   |
+LL |     let _: &[i32] = &[0];
+   |                     +
 
 error: aborting due to previous error
 

tests/ui/inference/deref-suggestion.stderr

@@ -98,19 +98,23 @@ error[E0308]: mismatched types
   --> $DIR/deref-suggestion.rs:40:17
    |
 LL |     let s = S { u };
-   |                 ^
-   |                 |
-   |                 expected `&u32`, found integer
-   |                 help: consider borrowing here: `u: &u`
+   |                 ^ expected `&u32`, found integer
+   |
+help: consider borrowing here
+   |
+LL |     let s = S { u: &u };
+   |                 ++++
 
 error[E0308]: mismatched types
   --> $DIR/deref-suggestion.rs:42:20
    |
 LL |     let s = S { u: u };
-   |                    ^
-   |                    |
-   |                    expected `&u32`, found integer
-   |                    help: consider borrowing here: `&u`
+   |                    ^ expected `&u32`, found integer
+   |
+help: consider borrowing here
+   |
+LL |     let s = S { u: &u };
+   |                    +
 
 error[E0308]: mismatched types
   --> $DIR/deref-suggestion.rs:45:17

tests/ui/issues/issue-11374.stderr

@@ -2,10 +2,8 @@ error[E0308]: mismatched types
   --> $DIR/issue-11374.rs:26:15
    |
 LL |     c.read_to(v);
-   |       ------- ^
-   |       |       |
-   |       |       expected `&mut [u8]`, found `Vec<_>`
-   |       |       help: consider mutably borrowing here: `&mut v`
+   |       ------- ^ expected `&mut [u8]`, found `Vec<_>`
+   |       |
    |       arguments to this method are incorrect
    |
    = note: expected mutable reference `&mut [u8]`
@@ -15,6 +13,10 @@ note: method defined here
    |
 LL |     pub fn read_to(&mut self, vec: &mut [u8]) {
    |            ^^^^^^^            --------------
+help: consider mutably borrowing here
+   |
+LL |     c.read_to(&mut v);
+   |               ++++
 
 error: aborting due to previous error
 

tests/ui/issues/issue-17033.stderr

@@ -2,11 +2,14 @@ error[E0308]: mismatched types
   --> $DIR/issue-17033.rs:2:10
    |
 LL |     (*p)(())
-   |     ---- ^^
-   |     |    |
-   |     |    expected `&mut ()`, found `()`
-   |     |    help: consider mutably borrowing here: `&mut ()`
+   |     ---- ^^ expected `&mut ()`, found `()`
+   |     |
    |     arguments to this function are incorrect
+   |
+help: consider mutably borrowing here
+   |
+LL |     (*p)(&mut ())
+   |          ++++
 
 error: aborting due to previous error
 

tests/ui/issues/issue-18819.stderr

@@ -19,7 +19,7 @@ LL | fn print_x(_: &dyn Foo<Item=bool>, extra: &str) {
 help: consider borrowing here
    |
 LL |     print_x(&X);
-   |             ~~
+   |             +
 help: provide the argument
    |
 LL |     print_x(/* &dyn Foo<Item = bool> */, /* &str */);

tests/ui/issues/issue-46302.stderr

@@ -2,10 +2,12 @@ error[E0308]: mismatched types
   --> $DIR/issue-46302.rs:3:27
    |
 LL |   let u: &str = if true { s[..2] } else { s };
-   |                           ^^^^^^
-   |                           |
-   |                           expected `&str`, found `str`
-   |                           help: consider borrowing here: `&s[..2]`
+   |                           ^^^^^^ expected `&str`, found `str`
+   |
+help: consider borrowing here
+   |
+LL |   let u: &str = if true { &s[..2] } else { s };
+   |                           +
 
 error: aborting due to previous error
 

tests/ui/issues/issue-61106.stderr

@@ -2,17 +2,19 @@ error[E0308]: mismatched types
   --> $DIR/issue-61106.rs:3:9
    |
 LL |     foo(x.clone());
-   |     --- ^^^^^^^^^
-   |     |   |
-   |     |   expected `&str`, found `String`
-   |     |   help: consider borrowing here: `&x`
+   |     --- ^^^^^^^^^ expected `&str`, found `String`
+   |     |
    |     arguments to this function are incorrect
    |
 note: function defined here
   --> $DIR/issue-61106.rs:6:4
    |
 LL | fn foo(_: &str) {}
    |    ^^^ -------
+help: consider borrowing here
+   |
+LL |     foo(&x.clone());
+   |         +
 
 error: aborting due to previous error
 

tests/ui/methods/method-self-arg-1.stderr

@@ -2,17 +2,19 @@ error[E0308]: mismatched types
   --> $DIR/method-self-arg-1.rs:11:14
    |
 LL |     Foo::bar(x);
-   |     -------- ^
-   |     |        |
-   |     |        expected `&Foo`, found `Foo`
-   |     |        help: consider borrowing here: `&x`
+   |     -------- ^ expected `&Foo`, found `Foo`
+   |     |
    |     arguments to this function are incorrect
    |
 note: method defined here
   --> $DIR/method-self-arg-1.rs:6:8
    |
 LL |     fn bar(&self) {}
    |        ^^^ -----
+help: consider borrowing here
+   |
+LL |     Foo::bar(&x);
+   |              +
 
 error[E0308]: mismatched types
   --> $DIR/method-self-arg-1.rs:13:14

tests/ui/mismatched_types/dont-point-return-on-E0308.stderr

@@ -2,17 +2,19 @@ error[E0308]: mismatched types
   --> $DIR/dont-point-return-on-E0308.rs:11:11
    |
 LL |         f(());
-   |         - ^^
-   |         | |
-   |         | expected `&()`, found `()`
-   |         | help: consider borrowing here: `&()`
+   |         - ^^ expected `&()`, found `()`
+   |         |
    |         arguments to this function are incorrect
    |
 note: function defined here
   --> $DIR/dont-point-return-on-E0308.rs:3:10
    |
 LL | async fn f(_: &()) {}
    |          ^ ------
+help: consider borrowing here
+   |
+LL |         f(&());
+   |           +
 
 error: aborting due to previous error
 

tests/ui/mut/mut-cross-borrowing.stderr

@@ -2,10 +2,8 @@ error[E0308]: mismatched types
   --> $DIR/mut-cross-borrowing.rs:7:7
    |
 LL |     f(x)
-   |     - ^
-   |     | |
-   |     | expected `&mut isize`, found `Box<{integer}>`
-   |     | help: consider mutably borrowing here: `&mut x`
+   |     - ^ expected `&mut isize`, found `Box<{integer}>`
+   |     |
    |     arguments to this function are incorrect
    |
    = note: expected mutable reference `&mut isize`
@@ -15,6 +13,10 @@ note: function defined here
    |
 LL | fn f(_: &mut isize) {}
    |    ^ -------------
+help: consider mutably borrowing here
+   |
+LL |     f(&mut x)
+   |       ++++
 
 error: aborting due to previous error