Rollup merge of #144376 - estebank:issue-143795, r=lcnr

Suggest unwrapping when private method name is available in inner type

Given

```rust
fn main() {
    let maybe_vec = Some(vec![1,2,3]);
    assert_eq!(maybe_vec.len(), 3);
}
```

suggest unwraping `maybe_vec` to call `.len()` on the `Vec<_>`.

```
error[E0624]: method `len` is private
  --> $DIR/enum-method-probe.rs:61:9
   |
LL |     res.len();
   |         ^^^ private method
  --> $SRC_DIR/core/src/option.rs:LL:COL
   |
   = note: private method defined here
   |
note: the method `len` exists on the type `Vec<{integer}>`
  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
help: consider using `Option::expect` to unwrap the `Vec<{integer}>` value, panicking if the value is an `Option::None`
   |
LL |     res.expect("REASON").len();
   |        +++++++++++++++++
```

When a method isn't available, we emit E0599, but when it is private we emit E0624. We now just invoke the same suggestion logic from the later that we already did in the former.

Fix rust-lang/rust#143795.

4 files changed, 34 insertions, 2 deletions

diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index dbfa7e6273c..e64af8fb7b3 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -264,6 +264,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     err.span_label(within_macro_span, "due to this macro variable");
                 }
                 self.suggest_valid_traits(&mut err, item_name, out_of_scope_traits, true);
+                self.suggest_unwrapping_inner_self(&mut err, source, rcvr_ty, item_name);
                 err.emit()
             }
 
diff --git a/tests/ui/suggestions/enum-method-probe.fixed b/tests/ui/suggestions/enum-method-probe.fixed
index e097fa8cc1d..b7fd6f112d5 100644
--- a/tests/ui/suggestions/enum-method-probe.fixed
+++ b/tests/ui/suggestions/enum-method-probe.fixed
@@ -56,4 +56,11 @@ fn test_option_in_unit_return() {
     //~| HELP consider using `Option::expect` to unwrap the `Foo` value, panicking if the value is an `Option::None`
 }
 
+fn test_option_private_method() {
+    let res: Option<_> = Some(vec![1, 2, 3]);
+    res.expect("REASON").len();
+    //~^ ERROR method `len` is private
+    //~| HELP consider using `Option::expect` to unwrap the `Vec<{integer}>` value, panicking if the value is an `Option::None`
+}
+
 fn main() {}
diff --git a/tests/ui/suggestions/enum-method-probe.rs b/tests/ui/suggestions/enum-method-probe.rs
index 665ee7d0aaa..cbb819b7c8c 100644
--- a/tests/ui/suggestions/enum-method-probe.rs
+++ b/tests/ui/suggestions/enum-method-probe.rs
@@ -56,4 +56,11 @@ fn test_option_in_unit_return() {
     //~| HELP consider using `Option::expect` to unwrap the `Foo` value, panicking if the value is an `Option::None`
 }
 
+fn test_option_private_method() {
+    let res: Option<_> = Some(vec![1, 2, 3]);
+    res.len();
+    //~^ ERROR method `len` is private
+    //~| HELP consider using `Option::expect` to unwrap the `Vec<{integer}>` value, panicking if the value is an `Option::None`
+}
+
 fn main() {}
diff --git a/tests/ui/suggestions/enum-method-probe.stderr b/tests/ui/suggestions/enum-method-probe.stderr
index 6ed14984f47..e66973d9d95 100644
--- a/tests/ui/suggestions/enum-method-probe.stderr
+++ b/tests/ui/suggestions/enum-method-probe.stderr
@@ -94,6 +94,23 @@ help: consider using `Option::expect` to unwrap the `Foo` value, panicking if th
 LL |     res.expect("REASON").get();
    |        +++++++++++++++++
 
-error: aborting due to 6 previous errors
+error[E0624]: method `len` is private
+  --> $DIR/enum-method-probe.rs:61:9
+   |
+LL |     res.len();
+   |         ^^^ private method
+  --> $SRC_DIR/core/src/option.rs:LL:COL
+   |
+   = note: private method defined here
+   |
+note: the method `len` exists on the type `Vec<{integer}>`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+help: consider using `Option::expect` to unwrap the `Vec<{integer}>` value, panicking if the value is an `Option::None`
+   |
+LL |     res.expect("REASON").len();
+   |        +++++++++++++++++
+
+error: aborting due to 7 previous errors
 
-For more information about this error, try `rustc --explain E0599`.
+Some errors have detailed explanations: E0599, E0624.
+For more information about an error, try `rustc --explain E0599`.