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Add test cases and address review comments

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This commit is contained in:
Esteban Küber 2020-08-22 17:24:26 -07:00
parent 5d2a935e6c
commit dc53cfea7e
5 changed files with 156 additions and 19 deletions
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10
compiler/rustc_infer/src/infer/error_reporting/mod.rs
View File

@ -617,14 +617,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
ref prior_arms,
last_ty,
scrut_hir_id,
suggest_box,
opt_suggest_box_span,
arm_span,
..
}) => match source {
hir::MatchSource::IfLetDesugar { .. } => {
let msg = "`if let` arms have incompatible types";
err.span_label(cause.span, msg);
if let Some(ret_sp) = suggest_box {
if let Some(ret_sp) = opt_suggest_box_span {
self.suggest_boxing_for_return_impl_trait(
err,
ret_sp,
@ -684,7 +684,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
Applicability::MachineApplicable,
);
}
if let Some(ret_sp) = suggest_box {
if let Some(ret_sp) = opt_suggest_box_span {
// Get return type span and point to it.
self.suggest_boxing_for_return_impl_trait(
err,
@ -699,7 +699,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
else_sp,
outer,
semicolon,
suggest_box,
opt_suggest_box_span,
}) => {
err.span_label(then, "expected because of this");
if let Some(sp) = outer {
@ -713,7 +713,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
Applicability::MachineApplicable,
);
}
if let Some(ret_sp) = suggest_box {
if let Some(ret_sp) = opt_suggest_box_span {
self.suggest_boxing_for_return_impl_trait(
err,
ret_sp,

4
compiler/rustc_middle/src/traits/mod.rs
View File

@ -350,7 +350,7 @@ pub struct MatchExpressionArmCause<'tcx> {
pub prior_arms: Vec<Span>,
pub last_ty: Ty<'tcx>,
pub scrut_hir_id: hir::HirId,
pub suggest_box: Option<Span>,
pub opt_suggest_box_span: Option<Span>,
}
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
@ -359,7 +359,7 @@ pub struct IfExpressionCause {
pub else_sp: Span,
pub outer: Option<Span>,
pub semicolon: Option<Span>,
pub suggest_box: Option<Span>,
pub opt_suggest_box_span: Option<Span>,
}
#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]

16
compiler/rustc_typeck/src/check/_match.rs
View File

@ -119,13 +119,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// When we have a `match` as a tail expression in a `fn` with a returned `impl Trait`
// we check if the different arms would work with boxed trait objects instead and
// provide a structured suggestion in that case.
let suggest_box = match (
let opt_suggest_box_span = match (
orig_expected,
self.body_id
.owner
.to_def_id()
.as_local()
.and_then(|id| self.ret_coercion_impl_trait.map(|ty| (id, ty))),
self.ret_coercion_impl_trait.map(|ty| (self.body_id.owner, ty)),
) {
(Expectation::ExpectHasType(expected), Some((id, ty)))
if self.in_tail_expr && self.can_coerce(arm_ty, expected) =>
@ -181,7 +177,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
&arm.body,
then_ty,
arm_ty,
suggest_box,
opt_suggest_box_span,
);
coercion.coerce(self, &cause, &arm.body, arm_ty);
}
@ -205,7 +201,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
prior_arms: other_arms.clone(),
last_ty: prior_arm_ty.unwrap(),
scrut_hir_id: scrut.hir_id,
suggest_box,
opt_suggest_box_span,
}),
),
};
@ -330,7 +326,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
else_expr: &'tcx hir::Expr<'tcx>,
then_ty: Ty<'tcx>,
else_ty: Ty<'tcx>,
suggest_box: Option<Span>,
opt_suggest_box_span: Option<Span>,
) -> ObligationCause<'tcx> {
let mut outer_sp = if self.tcx.sess.source_map().is_multiline(span) {
// The `if`/`else` isn't in one line in the output, include some context to make it
@ -421,7 +417,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
else_sp: error_sp,
outer: outer_sp,
semicolon: remove_semicolon,
suggest_box,
opt_suggest_box_span,
}),
)
}

35
src/test/ui/point-to-type-err-cause-on-impl-trait-return.rs
View File

@ -63,4 +63,39 @@ fn dog() -> impl std::fmt::Display {
}
}
fn hat() -> dyn std::fmt::Display { //~ ERROR return type cannot have an unboxed trait object
match 13 {
0 => {
return 0i32;
}
_ => {
1u32
}
}
}
fn pug() -> dyn std::fmt::Display { //~ ERROR return type cannot have an unboxed trait object
match 13 {
0 => 0i32,
1 => 1u32, //~ ERROR `match` arms have incompatible types
_ => 2u32,
}
}
fn man() -> dyn std::fmt::Display { //~ ERROR return type cannot have an unboxed trait object
if false {
0i32
} else {
1u32 //~ ERROR `if` and `else` have incompatible types
}
}
fn apt() -> impl std::fmt::Display {
if let Some(42) = Some(42) {
0i32
} else {
1u32 //~ ERROR `if` and `else` have incompatible types
}
}
fn main() {}

110
src/test/ui/point-to-type-err-cause-on-impl-trait-return.stderr
View File

@ -207,6 +207,112 @@ LL | 0 => Box::new(0i32),
LL | 1 => Box::new(1u32),
|
error: aborting due to 8 previous errors
error[E0308]: `if` and `else` have incompatible types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:97:9
|
LL | / if let Some(42) = Some(42) {
LL | | 0i32
| | ---- expected because of this
LL | | } else {
LL | | 1u32
| | ^^^^ expected `i32`, found `u32`
LL | | }
| |_____- `if` and `else` have incompatible types
|
help: you could change the return type to be a boxed trait object
|
LL | fn apt() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
help: if you change the return type to expect trait objects, box the returned expressions
|
LL | Box::new(0i32)
LL | } else {
LL | Box::new(1u32)
|
For more information about this error, try `rustc --explain E0308`.
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:66:13
|
LL | fn hat() -> dyn std::fmt::Display {
| ^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
= note: if all the returned values were of the same type you could use `impl std::fmt::Display` as the return type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: you can create a new `enum` with a variant for each returned type
help: return a boxed trait object instead
|
LL | fn hat() -> Box<dyn std::fmt::Display> {
LL | match 13 {
LL | 0 => {
LL | return Box::new(0i32);
LL | }
LL | _ => {
...
error[E0308]: `match` arms have incompatible types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:80:14
|
LL | / match 13 {
LL | | 0 => 0i32,
| | ---- this is found to be of type `i32`
LL | | 1 => 1u32,
| | ^^^^ expected `i32`, found `u32`
LL | | _ => 2u32,
LL | | }
| |_____- `match` arms have incompatible types
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:77:13
|
LL | fn pug() -> dyn std::fmt::Display {
| ^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
= note: if all the returned values were of the same type you could use `impl std::fmt::Display` as the return type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: you can create a new `enum` with a variant for each returned type
help: return a boxed trait object instead
|
LL | fn pug() -> Box<dyn std::fmt::Display> {
LL | match 13 {
LL | 0 => Box::new(0i32),
LL | 1 => Box::new(1u32),
LL | _ => Box::new(2u32),
|
error[E0308]: `if` and `else` have incompatible types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:89:9
|
LL | / if false {
LL | | 0i32
| | ---- expected because of this
LL | | } else {
LL | | 1u32
| | ^^^^ expected `i32`, found `u32`
LL | | }
| |_____- `if` and `else` have incompatible types
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:85:13
|
LL | fn man() -> dyn std::fmt::Display {
| ^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
= note: if all the returned values were of the same type you could use `impl std::fmt::Display` as the return type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: you can create a new `enum` with a variant for each returned type
help: return a boxed trait object instead
|
LL | fn man() -> Box<dyn std::fmt::Display> {
LL | if false {
LL | Box::new(0i32)
LL | } else {
LL | Box::new(1u32)
|
error: aborting due to 14 previous errors
Some errors have detailed explanations: E0308, E0746.
For more information about an error, try `rustc --explain E0308`.