Rollup merge of #59859 - davidtwco:issue-59756, r=cramertj

Suggest removing `?` to resolve type errors.

Fixes #59756.
This commit is contained in:
Mazdak Farrokhzad 2019-04-12 20:36:13 +02:00 committed by GitHub
commit 2bc127dcc7
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8 changed files with 84 additions and 2 deletions

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@ -604,13 +604,39 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
source,
ref prior_arms,
last_ty,
discrim_hir_id,
..
} => match source {
hir::MatchSource::IfLetDesugar { .. } => {
let msg = "`if let` arms have incompatible types";
err.span_label(cause.span, msg);
}
hir::MatchSource::TryDesugar => {}
hir::MatchSource::TryDesugar => {
if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found {
let discrim_expr = self.tcx.hir().expect_expr_by_hir_id(discrim_hir_id);
let discrim_ty = if let hir::ExprKind::Call(_, args) = &discrim_expr.node {
let arg_expr = args.first().expect("try desugaring call w/out arg");
self.in_progress_tables.and_then(|tables| {
tables.borrow().expr_ty_opt(arg_expr)
})
} else {
bug!("try desugaring w/out call expr as discriminant");
};
match discrim_ty {
Some(ty) if expected == ty => {
let source_map = self.tcx.sess.source_map();
err.span_suggestion(
source_map.end_point(cause.span),
"try removing this `?`",
"".to_string(),
Applicability::MachineApplicable,
);
},
_ => {},
}
}
}
_ => {
let msg = "`match` arms have incompatible types";
err.span_label(cause.span, msg);

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@ -226,6 +226,7 @@ pub enum ObligationCauseCode<'tcx> {
source: hir::MatchSource,
prior_arms: Vec<Span>,
last_ty: Ty<'tcx>,
discrim_hir_id: hir::HirId,
},
/// Computing common supertype in the pattern guard for the arms of a match expression

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@ -519,6 +519,7 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
source,
ref prior_arms,
last_ty,
discrim_hir_id,
} => {
tcx.lift(&last_ty).map(|last_ty| {
super::MatchExpressionArm {
@ -526,6 +527,7 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
source,
prior_arms: prior_arms.clone(),
last_ty,
discrim_hir_id,
}
})
}

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@ -732,6 +732,7 @@ https://doc.rust-lang.org/reference/types.html#trait-objects");
source: match_src,
prior_arms: other_arms.clone(),
last_ty: prior_arm_ty.unwrap(),
discrim_hir_id: discrim.hir_id,
})
};
coercion.coerce(self, &cause, &arm.body, arm_ty);

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@ -0,0 +1,17 @@
// run-rustfix
#![allow(warnings)]
struct A;
struct B;
fn foo() -> Result<A, B> {
Ok(A)
}
fn bar() -> Result<A, B> {
foo()
//~^ ERROR try expression alternatives have incompatible types [E0308]
}
fn main() {}

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@ -0,0 +1,17 @@
// run-rustfix
#![allow(warnings)]
struct A;
struct B;
fn foo() -> Result<A, B> {
Ok(A)
}
fn bar() -> Result<A, B> {
foo()?
//~^ ERROR try expression alternatives have incompatible types [E0308]
}
fn main() {}

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@ -0,0 +1,15 @@
error[E0308]: try expression alternatives have incompatible types
--> $DIR/issue-59756.rs:13:5
|
LL | foo()?
| ^^^^^-
| | |
| | help: try removing this `?`
| expected enum `std::result::Result`, found struct `A`
|
= note: expected type `std::result::Result<A, B>`
found type `A`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0308`.

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@ -2,7 +2,10 @@ error[E0308]: try expression alternatives have incompatible types
--> $DIR/issue-51632-try-desugar-incompatible-types.rs:8:5
|
LL | missing_discourses()?
| ^^^^^^^^^^^^^^^^^^^^^ expected enum `std::result::Result`, found isize
| ^^^^^^^^^^^^^^^^^^^^-
| | |
| | help: try removing this `?`
| expected enum `std::result::Result`, found isize
|
= note: expected type `std::result::Result<isize, ()>`
found type `isize`