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Reduce diagram mess in 'match arms have incompatible types' error

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This commit is contained in:
David Tolnay 2020-10-22 14:20:02 -07:00
parent f82adf5bdb
commit b0059500f6
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GPG Key ID: F9BA143B95FF6D82
4 changed files with 38 additions and 28 deletions
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16
compiler/rustc_infer/src/infer/error_reporting/mod.rs
View File

@ -619,6 +619,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
scrut_hir_id,
opt_suggest_box_span,
arm_span,
scrut_span,
..
}) => match source {
hir::MatchSource::IfLetDesugar { .. } => {
@ -664,18 +665,29 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
Some(ty::error::ExpectedFound { expected, .. }) => expected,
_ => last_ty,
});
let msg = "`match` arms have incompatible types";
err.span_label(cause.span, msg);
let source_map = self.tcx.sess.source_map();
let mut any_multiline_arm = source_map.is_multiline(arm_span);
if prior_arms.len() <= 4 {
for sp in prior_arms {
any_multiline_arm |= source_map.is_multiline(*sp);
err.span_label(*sp, format!("this is found to be of type `{}`", t));
}
} else if let Some(sp) = prior_arms.last() {
any_multiline_arm |= source_map.is_multiline(*sp);
err.span_label(
*sp,
format!("this and all prior arms are found to be of type `{}`", t),
);
}
let outer_error_span = if any_multiline_arm {
// Cover just `match` and the scrutinee expression, not
// the entire match body, to reduce diagram noise.
cause.span.shrink_to_lo().to(scrut_span)
} else {
cause.span
};
let msg = "`match` arms have incompatible types";
err.span_label(outer_error_span, msg);
if let Some(sp) = semi_span {
err.span_suggestion_short(
sp,

1
compiler/rustc_middle/src/traits/mod.rs
View File

@ -343,6 +343,7 @@ static_assert_size!(ObligationCauseCode<'_>, 32);
#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
pub struct MatchExpressionArmCause<'tcx> {
pub arm_span: Span,
pub scrut_span: Span,
pub semi_span: Option<Span>,
pub source: hir::MatchSource,
pub prior_arms: Vec<Span>,

1
compiler/rustc_typeck/src/check/_match.rs
View File

@ -201,6 +201,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
expr.span,
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
arm_span,
scrut_span: scrut.span,
semi_span,
source: match_src,
prior_arms: other_arms.clone(),

48
src/test/ui/match/match-incompat-type-semi.stderr
View File

@ -56,36 +56,32 @@ LL | | };
error[E0308]: `match` arms have incompatible types
--> $DIR/match-incompat-type-semi.rs:39:17
|
LL | let _ = match Some(42) {
| _____________-
LL | | Some(x) => {
LL | | x
| | - this is found to be of type `{integer}`
LL | | },
LL | | None => {
| |_________________^
LL | || },
| ||_________^ expected integer, found `()`
LL | | };
| |_____- `match` arms have incompatible types
LL | let _ = match Some(42) {
| -------------- `match` arms have incompatible types
LL | Some(x) => {
LL | x
| - this is found to be of type `{integer}`
LL | },
LL | None => {
| _________________^
LL | | },
| |_________^ expected integer, found `()`
error[E0308]: `match` arms have incompatible types
--> $DIR/match-incompat-type-semi.rs:50:17
|
LL | let _ = match Some(42) {
| _____________-
LL | | Some(x) => "rust-lang.org"
| |____________________-
LL | || .chars()
LL | || .skip(1)
LL | || .chain(Some(x as u8 as char))
LL | || .take(10)
LL | || .any(char::is_alphanumeric),
| ||_______________________________________- this is found to be of type `bool`
LL | | None => {}
| | ^^ expected `bool`, found `()`
LL | | };
| |_____- `match` arms have incompatible types
LL | let _ = match Some(42) {
| -------------- `match` arms have incompatible types
LL | Some(x) => "rust-lang.org"
| ____________________-
LL | | .chars()
LL | | .skip(1)
LL | | .chain(Some(x as u8 as char))
LL | | .take(10)
LL | | .any(char::is_alphanumeric),
| |_______________________________________- this is found to be of type `bool`
LL | None => {}
| ^^ expected `bool`, found `()`
error: aborting due to 5 previous errors