Add "dereference boxed value" suggestion.
This commit adds a `help: consider dereferencing the boxed value`
suggestion to discriminants of match statements when the match arms have
type `T` and the discriminant has type `Box<T>`.
diff --git a/src/librustc/infer/error_reporting/mod.rs b/src/librustc/infer/error_reporting/mod.rs
index 2995b25..35f6e6a 100644
--- a/src/librustc/infer/error_reporting/mod.rs
+++ b/src/librustc/infer/error_reporting/mod.rs
@@ -485,12 +485,29 @@
}
}
- fn note_error_origin(&self, err: &mut DiagnosticBuilder<'tcx>, cause: &ObligationCause<'tcx>) {
+ fn note_error_origin(
+ &self,
+ err: &mut DiagnosticBuilder<'tcx>,
+ cause: &ObligationCause<'tcx>,
+ exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
+ ) {
match cause.code {
ObligationCauseCode::MatchExpressionArmPattern { span, ty } => {
if ty.is_suggestable() { // don't show type `_`
err.span_label(span, format!("this match expression has type `{}`", ty));
}
+ if let Some(ty::error::ExpectedFound { found, .. }) = exp_found {
+ if ty.is_box() && ty.boxed_ty() == found {
+ if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
+ err.span_suggestion_with_applicability(
+ span,
+ "consider dereferencing the boxed value",
+ format!("*{}", snippet),
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+ }
}
ObligationCauseCode::MatchExpressionArm { arm_span, source } => match source {
hir::MatchSource::IfLetDesugar { .. } => {
@@ -1013,7 +1030,7 @@
// It reads better to have the error origin as the final
// thing.
- self.note_error_origin(diag, &cause);
+ self.note_error_origin(diag, &cause, exp_found);
}
/// When encountering a case where `.as_ref()` on a `Result` or `Option` would be appropriate,
diff --git a/src/test/ui/issues/issue-57741-1.rs b/src/test/ui/issues/issue-57741-1.rs
new file mode 100644
index 0000000..d0aae23
--- /dev/null
+++ b/src/test/ui/issues/issue-57741-1.rs
@@ -0,0 +1,18 @@
+#![allow(warnings)]
+
+// This tests that the `help: consider dereferencing the boxed value` suggestion isn't made
+// because the box doesn't deref to the type of the arm.
+
+enum S {
+ A { a: usize },
+ B { b: usize },
+}
+
+fn main() {
+ let x = Box::new(3u32);
+ let y = match x {
+ S::A { a } | S::B { b: a } => a,
+ //~^ ERROR mismatched types [E0308]
+ //~^^ ERROR mismatched types [E0308]
+ };
+}
diff --git a/src/test/ui/issues/issue-57741-1.stderr b/src/test/ui/issues/issue-57741-1.stderr
new file mode 100644
index 0000000..d36424b
--- /dev/null
+++ b/src/test/ui/issues/issue-57741-1.stderr
@@ -0,0 +1,25 @@
+error[E0308]: mismatched types
+ --> $DIR/issue-57741-1.rs:14:9
+ |
+LL | let y = match x {
+ | - this match expression has type `std::boxed::Box<u32>`
+LL | S::A { a } | S::B { b: a } => a,
+ | ^^^^^^^^^^ expected struct `std::boxed::Box`, found enum `S`
+ |
+ = note: expected type `std::boxed::Box<u32>`
+ found type `S`
+
+error[E0308]: mismatched types
+ --> $DIR/issue-57741-1.rs:14:22
+ |
+LL | let y = match x {
+ | - this match expression has type `std::boxed::Box<u32>`
+LL | S::A { a } | S::B { b: a } => a,
+ | ^^^^^^^^^^^^^ expected struct `std::boxed::Box`, found enum `S`
+ |
+ = note: expected type `std::boxed::Box<u32>`
+ found type `S`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/issues/issue-57741.fixed b/src/test/ui/issues/issue-57741.fixed
new file mode 100644
index 0000000..4cae080
--- /dev/null
+++ b/src/test/ui/issues/issue-57741.fixed
@@ -0,0 +1,31 @@
+// run-rustfix
+
+#![allow(warnings)]
+
+// This tests that the `help: consider dereferencing the boxed value` suggestion is made and works.
+
+enum S {
+ A { a: usize },
+ B { b: usize },
+}
+
+enum T {
+ A(usize),
+ B(usize),
+}
+
+fn main() {
+ let x = Box::new(T::A(3));
+ let y = match *x {
+ T::A(a) | T::B(a) => a,
+ //~^ ERROR mismatched types [E0308]
+ //~^^ ERROR mismatched types [E0308]
+ };
+
+ let x = Box::new(S::A { a: 3 });
+ let y = match *x {
+ S::A { a } | S::B { b: a } => a,
+ //~^ ERROR mismatched types [E0308]
+ //~^^ ERROR mismatched types [E0308]
+ };
+}
diff --git a/src/test/ui/issues/issue-57741.rs b/src/test/ui/issues/issue-57741.rs
new file mode 100644
index 0000000..e265829
--- /dev/null
+++ b/src/test/ui/issues/issue-57741.rs
@@ -0,0 +1,31 @@
+// run-rustfix
+
+#![allow(warnings)]
+
+// This tests that the `help: consider dereferencing the boxed value` suggestion is made and works.
+
+enum S {
+ A { a: usize },
+ B { b: usize },
+}
+
+enum T {
+ A(usize),
+ B(usize),
+}
+
+fn main() {
+ let x = Box::new(T::A(3));
+ let y = match x {
+ T::A(a) | T::B(a) => a,
+ //~^ ERROR mismatched types [E0308]
+ //~^^ ERROR mismatched types [E0308]
+ };
+
+ let x = Box::new(S::A { a: 3 });
+ let y = match x {
+ S::A { a } | S::B { b: a } => a,
+ //~^ ERROR mismatched types [E0308]
+ //~^^ ERROR mismatched types [E0308]
+ };
+}
diff --git a/src/test/ui/issues/issue-57741.stderr b/src/test/ui/issues/issue-57741.stderr
new file mode 100644
index 0000000..a26b1d20
--- /dev/null
+++ b/src/test/ui/issues/issue-57741.stderr
@@ -0,0 +1,59 @@
+error[E0308]: mismatched types
+ --> $DIR/issue-57741.rs:20:9
+ |
+LL | let y = match x {
+ | -
+ | |
+ | this match expression has type `std::boxed::Box<T>`
+ | help: consider dereferencing the boxed value: `*x`
+LL | T::A(a) | T::B(a) => a,
+ | ^^^^^^^ expected struct `std::boxed::Box`, found enum `T`
+ |
+ = note: expected type `std::boxed::Box<T>`
+ found type `T`
+
+error[E0308]: mismatched types
+ --> $DIR/issue-57741.rs:20:19
+ |
+LL | let y = match x {
+ | -
+ | |
+ | this match expression has type `std::boxed::Box<T>`
+ | help: consider dereferencing the boxed value: `*x`
+LL | T::A(a) | T::B(a) => a,
+ | ^^^^^^^ expected struct `std::boxed::Box`, found enum `T`
+ |
+ = note: expected type `std::boxed::Box<T>`
+ found type `T`
+
+error[E0308]: mismatched types
+ --> $DIR/issue-57741.rs:27:9
+ |
+LL | let y = match x {
+ | -
+ | |
+ | this match expression has type `std::boxed::Box<S>`
+ | help: consider dereferencing the boxed value: `*x`
+LL | S::A { a } | S::B { b: a } => a,
+ | ^^^^^^^^^^ expected struct `std::boxed::Box`, found enum `S`
+ |
+ = note: expected type `std::boxed::Box<S>`
+ found type `S`
+
+error[E0308]: mismatched types
+ --> $DIR/issue-57741.rs:27:22
+ |
+LL | let y = match x {
+ | -
+ | |
+ | this match expression has type `std::boxed::Box<S>`
+ | help: consider dereferencing the boxed value: `*x`
+LL | S::A { a } | S::B { b: a } => a,
+ | ^^^^^^^^^^^^^ expected struct `std::boxed::Box`, found enum `S`
+ |
+ = note: expected type `std::boxed::Box<S>`
+ found type `S`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
