Rollup merge of #91545 - compiler-errors:deref-suggestion-improvements, r=estebank

Generalize "remove `&`"  and "add `*`" suggestions to more than one deref

Suggest removing more than one `&` and `&mut`, along with suggesting adding more than one `*` (or a combination of the two).

r? `@estebank`
(since you're experienced with these types of suggestions, feel free to reassign)

5 files changed, 120 insertions, 0 deletions

diff --git a/src/test/ui/parser/expr-as-stmt-2.stderr b/src/test/ui/parser/expr-as-stmt-2.stderr
index 2b6314c38ce..b7516babc13 100644
--- a/src/test/ui/parser/expr-as-stmt-2.stderr
+++ b/src/test/ui/parser/expr-as-stmt-2.stderr
@@ -36,6 +36,11 @@ LL | /     &&
 LL | |     if let Some(y) = a { true } else { false }
    | |______________________________________________^ expected `bool`, found `&&bool`
    |
+help: consider removing the `&&`
+   |
+LL -     &&
+LL +     if let Some(y) = a { true } else { false }
+   | 
 help: parentheses are required to parse this as an expression
    |
 LL |     (if let Some(x) = a { true } else { false })
diff --git a/src/test/ui/parser/expr-as-stmt.stderr b/src/test/ui/parser/expr-as-stmt.stderr
index df0e4dcb16e..e63da52c8fe 100644
--- a/src/test/ui/parser/expr-as-stmt.stderr
+++ b/src/test/ui/parser/expr-as-stmt.stderr
@@ -170,6 +170,11 @@ LL | fn revenge_from_mars() -> bool {
 LL |     { true } && { true }
    |              ^^^^^^^^^^^ expected `bool`, found `&&bool`
    |
+help: consider removing the `&&`
+   |
+LL -     { true } && { true }
+LL +     { true } { true }
+   | 
 help: parentheses are required to parse this as an expression
    |
 LL |     ({ true }) && { true }
diff --git a/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr b/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr
index 4c830554d43..897de54a7bf 100644
--- a/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr
+++ b/src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr
@@ -676,6 +676,12 @@ error[E0308]: mismatched types
    |
 LL |     if let Range { start: true, end } = t..&&false {}
    |                                            ^^^^^^^ expected `bool`, found `&&bool`
+   |
+help: consider removing the `&&`
+   |
+LL -     if let Range { start: true, end } = t..&&false {}
+LL +     if let Range { start: true, end } = t..false {}
+   | 
 
 error[E0308]: mismatched types
   --> $DIR/disallowed-positions.rs:83:8
@@ -866,6 +872,12 @@ error[E0308]: mismatched types
    |
 LL |     while let Range { start: true, end } = t..&&false {}
    |                                               ^^^^^^^ expected `bool`, found `&&bool`
+   |
+help: consider removing the `&&`
+   |
+LL -     while let Range { start: true, end } = t..&&false {}
+LL +     while let Range { start: true, end } = t..false {}
+   | 
 
 error[E0308]: mismatched types
   --> $DIR/disallowed-positions.rs:147:11
diff --git a/src/test/ui/typeck/deref-multi.rs b/src/test/ui/typeck/deref-multi.rs
new file mode 100644
index 00000000000..3dc4771fefb
--- /dev/null
+++ b/src/test/ui/typeck/deref-multi.rs
@@ -0,0 +1,26 @@
+fn a(x: &&i32) -> i32 {
+    x
+    //~^ ERROR mismatched types
+}
+
+fn a2(x: &&&&&i32) -> i32 {
+    x
+    //~^ ERROR mismatched types
+}
+
+fn b(x: &i32) -> i32 {
+    &x
+    //~^ ERROR mismatched types
+}
+
+fn c(x: Box<i32>) -> i32 {
+    &x
+    //~^ ERROR mismatched types
+}
+
+fn d(x: std::sync::Mutex<&i32>) -> i32 {
+    x.lock().unwrap()
+    //~^ ERROR mismatched types
+}
+
+fn main() {}
diff --git a/src/test/ui/typeck/deref-multi.stderr b/src/test/ui/typeck/deref-multi.stderr
new file mode 100644
index 00000000000..bd6575c73d2
--- /dev/null
+++ b/src/test/ui/typeck/deref-multi.stderr
@@ -0,0 +1,72 @@
+error[E0308]: mismatched types
+  --> $DIR/deref-multi.rs:2:5
+   |
+LL | fn a(x: &&i32) -> i32 {
+   |                   --- expected `i32` because of return type
+LL |     x
+   |     ^ expected `i32`, found `&&i32`
+   |
+help: consider dereferencing the borrow
+   |
+LL |     **x
+   |     ++
+
+error[E0308]: mismatched types
+  --> $DIR/deref-multi.rs:7:5
+   |
+LL | fn a2(x: &&&&&i32) -> i32 {
+   |                       --- expected `i32` because of return type
+LL |     x
+   |     ^ expected `i32`, found `&&&&&i32`
+   |
+help: consider dereferencing the borrow
+   |
+LL |     *****x
+   |     +++++
+
+error[E0308]: mismatched types
+  --> $DIR/deref-multi.rs:12:5
+   |
+LL | fn b(x: &i32) -> i32 {
+   |                  --- expected `i32` because of return type
+LL |     &x
+   |     ^^ expected `i32`, found `&&i32`
+   |
+help: consider removing the `&` and dereferencing the borrow instead
+   |
+LL |     *x
+   |     ~
+
+error[E0308]: mismatched types
+  --> $DIR/deref-multi.rs:17:5
+   |
+LL | fn c(x: Box<i32>) -> i32 {
+   |                      --- expected `i32` because of return type
+LL |     &x
+   |     ^^ expected `i32`, found `&Box<i32>`
+   |
+   = note:   expected type `i32`
+           found reference `&Box<i32>`
+help: consider removing the `&` and dereferencing the borrow instead
+   |
+LL |     *x
+   |     ~
+
+error[E0308]: mismatched types
+  --> $DIR/deref-multi.rs:22:5
+   |
+LL | fn d(x: std::sync::Mutex<&i32>) -> i32 {
+   |                                    --- expected `i32` because of return type
+LL |     x.lock().unwrap()
+   |     ^^^^^^^^^^^^^^^^^ expected `i32`, found struct `MutexGuard`
+   |
+   = note: expected type `i32`
+            found struct `MutexGuard<'_, &i32>`
+help: consider dereferencing the type
+   |
+LL |     **x.lock().unwrap()
+   |     ++
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0308`.