Rollup merge of #99438 - WaffleLapkin:dont_wrap_in_non_zero, r=compiler-errors

Improve suggestions for `NonZeroT` <- `T` coercion error

Currently, when encountering a type mismatch error with `NonZeroT` and `T` (for example `NonZeroU8` and `u8`) we errorneusly suggest wrapping expression in `NonZeroT`:
```text
error[E0308]: mismatched types
 --> ./t.rs:7:35
  |
7 |     let _: std::num::NonZeroU64 = 1;
  |            --------------------   ^ expected struct `NonZeroU64`, found integer
  |            |
  |            expected due to this
  |
help: try wrapping the expression in `std::num::NonZeroU64`
  |
7 |     let _: std::num::NonZeroU64 = std::num::NonZeroU64(1);
  |                                   +++++++++++++++++++++ +
```

I've removed this suggestion and added suggestions to call `new` (for `Option<NonZeroT>` <- `T` case) or `new` and `unwrap` (for `NonZeroT` <- `T` case):

```text
error[E0308]: mismatched types
 --> ./t.rs:7:35
  |
7 |     let _: std::num::NonZeroU64 = 1;
  |            --------------------   ^ expected struct `NonZeroU64`, found integer
  |            |
  |            expected due to this
  |
help: Consider calling `NonZeroU64::new`
  |
7 |     let _: std::num::NonZeroU64 = NonZeroU64::new(1).unwrap();
  |                                   ++++++++++++++++ ++++++++++

error[E0308]: mismatched types
 --> ./t.rs:8:43
  |
8 |     let _: Option<std::num::NonZeroU64> = 1;
  |            ----------------------------   ^ expected enum `Option`, found integer
  |            |
  |            expected due to this
  |
  = note: expected enum `Option<NonZeroU64>`
             found type `{integer}`
help: Consider calling `NonZeroU64::new`
  |
8 |     let _: Option<std::num::NonZeroU64> = NonZeroU64::new(1);
  |                                           ++++++++++++++++ +
```

r? `@compiler-errors`

4 files changed, 123 insertions, 0 deletions

diff --git a/src/test/ui/mismatched_types/non_zero_assigned_something.rs b/src/test/ui/mismatched_types/non_zero_assigned_something.rs
new file mode 100644
index 00000000000..d2adbe01c18
--- /dev/null
+++ b/src/test/ui/mismatched_types/non_zero_assigned_something.rs
@@ -0,0 +1,9 @@
+fn main() {
+    let _: std::num::NonZeroU64 = 1;
+    //~^ ERROR mismatched types
+    //~| HELP  consider calling `NonZeroU64::new`
+
+    let _: Option<std::num::NonZeroU64> = 1;
+    //~^ ERROR mismatched types
+    //~| HELP  consider calling `NonZeroU64::new`
+}
diff --git a/src/test/ui/mismatched_types/non_zero_assigned_something.stderr b/src/test/ui/mismatched_types/non_zero_assigned_something.stderr
new file mode 100644
index 00000000000..d4b2c902f9b
--- /dev/null
+++ b/src/test/ui/mismatched_types/non_zero_assigned_something.stderr
@@ -0,0 +1,31 @@
+error[E0308]: mismatched types
+  --> $DIR/non_zero_assigned_something.rs:2:35
+   |
+LL |     let _: std::num::NonZeroU64 = 1;
+   |            --------------------   ^ expected struct `NonZeroU64`, found integer
+   |            |
+   |            expected due to this
+   |
+help: consider calling `NonZeroU64::new`
+   |
+LL |     let _: std::num::NonZeroU64 = NonZeroU64::new(1).unwrap();
+   |                                   ++++++++++++++++ ++++++++++
+
+error[E0308]: mismatched types
+  --> $DIR/non_zero_assigned_something.rs:6:43
+   |
+LL |     let _: Option<std::num::NonZeroU64> = 1;
+   |            ----------------------------   ^ expected enum `Option`, found integer
+   |            |
+   |            expected due to this
+   |
+   = note: expected enum `Option<NonZeroU64>`
+              found type `{integer}`
+help: consider calling `NonZeroU64::new`
+   |
+LL |     let _: Option<std::num::NonZeroU64> = NonZeroU64::new(1);
+   |                                           ++++++++++++++++ +
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/mismatched_types/wrap-suggestion-privacy.rs b/src/test/ui/mismatched_types/wrap-suggestion-privacy.rs
new file mode 100644
index 00000000000..63cb1a12991
--- /dev/null
+++ b/src/test/ui/mismatched_types/wrap-suggestion-privacy.rs
@@ -0,0 +1,24 @@
+mod inner {
+    pub struct Wrapper<T>(T);
+}
+
+fn needs_wrapper(t: inner::Wrapper<i32>) {}
+fn needs_wrapping(t: std::num::Wrapping<i32>) {}
+fn needs_ready(t: std::future::Ready<i32>) {}
+
+fn main() {
+    // Suggest wrapping expression because type is local
+    // and its privacy can be easily changed
+    needs_wrapper(0);
+    //~^ ERROR mismatched types
+    //~| HELP  try wrapping the expression in `inner::Wrapper`
+
+    // Suggest wrapping expression because field is accessible
+    needs_wrapping(0);
+    //~^ ERROR mismatched types
+    //~| HELP  try wrapping the expression in `std::num::Wrapping`
+
+    // Do not suggest wrapping expression
+    needs_ready(Some(0));
+    //~^ ERROR mismatched types
+}
diff --git a/src/test/ui/mismatched_types/wrap-suggestion-privacy.stderr b/src/test/ui/mismatched_types/wrap-suggestion-privacy.stderr
new file mode 100644
index 00000000000..e8eb8d263ec
--- /dev/null
+++ b/src/test/ui/mismatched_types/wrap-suggestion-privacy.stderr
@@ -0,0 +1,59 @@
+error[E0308]: mismatched types
+  --> $DIR/wrap-suggestion-privacy.rs:12:19
+   |
+LL |     needs_wrapper(0);
+   |     ------------- ^ expected struct `Wrapper`, found integer
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Wrapper<i32>`
+                found type `{integer}`
+note: function defined here
+  --> $DIR/wrap-suggestion-privacy.rs:5:4
+   |
+LL | fn needs_wrapper(t: inner::Wrapper<i32>) {}
+   |    ^^^^^^^^^^^^^ ----------------------
+help: try wrapping the expression in `inner::Wrapper` (its field is private, but it's local to this crate and its privacy can be changed)
+   |
+LL |     needs_wrapper(inner::Wrapper(0));
+   |                   +++++++++++++++ +
+
+error[E0308]: mismatched types
+  --> $DIR/wrap-suggestion-privacy.rs:17:20
+   |
+LL |     needs_wrapping(0);
+   |     -------------- ^ expected struct `Wrapping`, found integer
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Wrapping<i32>`
+                found type `{integer}`
+note: function defined here
+  --> $DIR/wrap-suggestion-privacy.rs:6:4
+   |
+LL | fn needs_wrapping(t: std::num::Wrapping<i32>) {}
+   |    ^^^^^^^^^^^^^^ --------------------------
+help: try wrapping the expression in `std::num::Wrapping`
+   |
+LL |     needs_wrapping(std::num::Wrapping(0));
+   |                    +++++++++++++++++++ +
+
+error[E0308]: mismatched types
+  --> $DIR/wrap-suggestion-privacy.rs:22:17
+   |
+LL |     needs_ready(Some(0));
+   |     ----------- ^^^^^^^ expected struct `std::future::Ready`, found enum `Option`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `std::future::Ready<i32>`
+                found enum `Option<{integer}>`
+note: function defined here
+  --> $DIR/wrap-suggestion-privacy.rs:7:4
+   |
+LL | fn needs_ready(t: std::future::Ready<i32>) {}
+   |    ^^^^^^^^^^^ --------------------------
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.