Reweork incompatible match arms error
- Point at the body expression of the match arm with the type error. - Point at the prior match arms explicitely stating the evaluated type. - Point at the entire match expr in a secondary span, instead of primary. - For type errors in the first match arm, the cause is outside of the match, treat as implicit block error to give a more appropriate error.
This commit is contained in:
Esteban Küber
parent
825f355c74
commit
9e934e2215
@ -509,22 +509,27 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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}
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}
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}
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ObligationCauseCode::MatchExpressionArm { arm_span, source } => match source {
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ObligationCauseCode::MatchExpressionArm {
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source,
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ref prior_arms,
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..
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} => match source {
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hir::MatchSource::IfLetDesugar { .. } => {
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let msg = "`if let` arm with an incompatible type";
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if self.tcx.sess.source_map().is_multiline(arm_span) {
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err.span_note(arm_span, msg);
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} else {
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err.span_label(arm_span, msg);
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}
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let msg = "`if let` arms have incompatible types";
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err.span_label(cause.span, msg);
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}
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hir::MatchSource::TryDesugar => {}
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_ => {
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let msg = "match arm with an incompatible type";
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if self.tcx.sess.source_map().is_multiline(arm_span) {
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err.span_note(arm_span, msg);
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} else {
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err.span_label(arm_span, msg);
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let msg = "`match` arms have incompatible types";
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err.span_label(cause.span, msg);
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if prior_arms.len() < 4 {
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for (sp, ty) in prior_arms {
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err.span_label(*sp, format!("this is found to be of type `{}`", ty));
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}
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} else if let Some((sp, ty)) = prior_arms.last() {
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err.span_label(*sp, format!(
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"this and all prior arms are found to be of type `{}`", ty,
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));
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}
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}
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},
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@ -145,6 +145,7 @@ impl<'tcx> ObligationCause<'tcx> {
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ObligationCauseCode::StartFunctionType => {
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tcx.sess.source_map().def_span(self.span)
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}
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ObligationCauseCode::MatchExpressionArm { arm_span, .. } => arm_span,
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_ => self.span,
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}
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}
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@ -223,6 +224,7 @@ pub enum ObligationCauseCode<'tcx> {
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MatchExpressionArm {
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arm_span: Span,
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source: hir::MatchSource,
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prior_arms: Vec<(Span, Ty<'tcx>)>,
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},
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/// Computing common supertype in the pattern guard for the arms of a match expression
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@ -513,10 +513,16 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
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trait_item_def_id,
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}),
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super::ExprAssignable => Some(super::ExprAssignable),
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super::MatchExpressionArm { arm_span, source } => Some(super::MatchExpressionArm {
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super::MatchExpressionArm {
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arm_span,
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source: source,
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}),
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source,
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ref prior_arms,
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} => {
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let prior_arms = prior_arms.iter().filter_map(|(sp, ty)| {
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tcx.lift(ty).map(|ty| (*sp, ty))
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}).collect();
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Some(super::MatchExpressionArm { arm_span, source, prior_arms })
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}
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super::MatchExpressionArmPattern { span, ty } => {
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tcx.lift(&ty).map(|ty| super::MatchExpressionArmPattern { span, ty })
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}
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@ -689,6 +689,7 @@ https://doc.rust-lang.org/reference/types.html#trait-objects");
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CoerceMany::with_coercion_sites(coerce_first, arms)
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};
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let mut other_arms = vec![]; // used only for diagnostics
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for (i, (arm, pats_diverge)) in arms.iter().zip(all_arm_pats_diverge).enumerate() {
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if let Some(ref g) = arm.guard {
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self.diverges.set(pats_diverge);
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@ -709,17 +710,31 @@ https://doc.rust-lang.org/reference/types.html#trait-objects");
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_ => false
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};
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let arm_span = if let hir::ExprKind::Block(ref blk, _) = arm.body.node {
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// Point at the block expr instead of the entire block
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blk.expr.as_ref().map(|e| e.span).unwrap_or(arm.body.span)
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} else {
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arm.body.span
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};
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if is_if_let_fallback {
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let cause = self.cause(expr.span, ObligationCauseCode::IfExpressionWithNoElse);
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assert!(arm_ty.is_unit());
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coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
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} else {
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let cause = self.cause(expr.span, ObligationCauseCode::MatchExpressionArm {
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arm_span: arm.body.span,
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source: match_src
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});
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let cause = if i == 0 {
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// The reason for the first arm to fail is not that the match arms diverge,
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// but rather that there's a prior obligation that doesn't hold.
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self.cause(arm_span, ObligationCauseCode::BlockTailExpression(arm.body.id))
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} else {
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self.cause(expr.span, ObligationCauseCode::MatchExpressionArm {
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arm_span,
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source: match_src,
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prior_arms: other_arms.clone(),
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})
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};
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coercion.coerce(self, &cause, &arm.body, arm_ty);
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}
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other_arms.push((arm_span, arm_ty));
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}
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// We won't diverge unless the discriminant or all arms diverge.
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@ -1,10 +1,11 @@
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fn main() {
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if let Some(b) = None { //~ ERROR: `if let` arms have incompatible types
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//~^ expected (), found integer
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//~| expected type `()`
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//~| found type `{integer}`
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if let Some(b) = None {
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//~^ NOTE if let` arms have incompatible types
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()
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} else {
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1
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};
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//~^^ ERROR: `if let` arms have incompatible types
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//~| NOTE expected (), found integer
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//~| NOTE expected type `()`
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}
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@ -1,25 +1,17 @@
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error[E0308]: `if let` arms have incompatible types
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--> $DIR/if-let-arm-types.rs:2:5
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--> $DIR/if-let-arm-types.rs:6:9
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LL | / if let Some(b) = None { //~ ERROR: `if let` arms have incompatible types
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LL | | //~^ expected (), found integer
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LL | | //~| expected type `()`
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LL | | //~| found type `{integer}`
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... |
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LL | / if let Some(b) = None {
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LL | | //~^ NOTE if let` arms have incompatible types
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LL | | ()
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LL | | } else {
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LL | | 1
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| | ^ expected (), found integer
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LL | | };
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| |_____^ expected (), found integer
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| |_____- `if let` arms have incompatible types
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= note: expected type `()`
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found type `{integer}`
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note: `if let` arm with an incompatible type
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--> $DIR/if-let-arm-types.rs:7:12
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LL | } else {
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| ____________^
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LL | | 1
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LL | | };
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| |_____^
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error: aborting due to previous error
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@ -1,12 +1,14 @@
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fn main() {
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match Some(10) {
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//~^ ERROR match arms have incompatible types
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//~| expected type `bool`
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//~| found type `()`
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//~| expected bool, found ()
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//~^ NOTE `match` arms have incompatible types
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Some(5) => false,
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//~^ NOTE this is found to be of type `bool`
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Some(2) => true,
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//~^ NOTE this is found to be of type `bool`
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None => (),
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//~^ ERROR match arms have incompatible types
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//~| NOTE expected bool, found ()
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//~| NOTE expected type `bool`
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_ => true
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}
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}
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@ -1,16 +1,20 @@
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error[E0308]: match arms have incompatible types
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--> $DIR/issue-11319.rs:2:5
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--> $DIR/issue-11319.rs:8:20
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LL | / match Some(10) {
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LL | | //~^ ERROR match arms have incompatible types
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LL | | //~| expected type `bool`
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LL | | //~| found type `()`
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... |
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LL | | //~^ NOTE `match` arms have incompatible types
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LL | | Some(5) => false,
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| | ----- this is found to be of type `bool`
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LL | | //~^ NOTE this is found to be of type `bool`
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LL | | Some(2) => true,
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| | ---- this is found to be of type `bool`
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LL | | //~^ NOTE this is found to be of type `bool`
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LL | | None => (),
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| | -- match arm with an incompatible type
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| | ^^ expected bool, found ()
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... |
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LL | | _ => true
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LL | | }
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| |_____^ expected bool, found ()
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| |_____- `match` arms have incompatible types
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= note: expected type `bool`
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found type `()`
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@ -97,7 +97,7 @@ impl Debug for Player {
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}
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fn str_to_direction(to_parse: &str) -> RoomDirection {
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match to_parse { //~ ERROR match arms have incompatible types
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match to_parse {
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"w" | "west" => RoomDirection::West,
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"e" | "east" => RoomDirection::East,
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"n" | "north" => RoomDirection::North,
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@ -108,6 +108,7 @@ fn str_to_direction(to_parse: &str) -> RoomDirection {
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"down" => RoomDirection::Down,
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_ => None
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}
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//~^^ ERROR match arms have incompatible types
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}
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fn main() {
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@ -10,17 +10,19 @@ LL | Some(entry) => Ok(entry),
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| ^^^^^^^^^ ...but data from `room` is returned here
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error[E0308]: match arms have incompatible types
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--> $DIR/issue-17728.rs:100:5
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--> $DIR/issue-17728.rs:109:14
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LL | / match to_parse { //~ ERROR match arms have incompatible types
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LL | / match to_parse {
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LL | | "w" | "west" => RoomDirection::West,
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LL | | "e" | "east" => RoomDirection::East,
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LL | | "n" | "north" => RoomDirection::North,
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... |
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LL | | "down" => RoomDirection::Down,
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| | ------------------- this and all prior arms are found to be of type `RoomDirection`
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LL | | _ => None
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| | ---- match arm with an incompatible type
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| | ^^^^ expected enum `RoomDirection`, found enum `std::option::Option`
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LL | | }
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| |_____^ expected enum `RoomDirection`, found enum `std::option::Option`
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| |_____- `match` arms have incompatible types
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= note: expected type `RoomDirection`
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found type `std::option::Option<_>`
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@ -6,11 +6,11 @@ fn closure_to_loc() {
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fn closure_from_match() {
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let x = match 1usize {
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//~^ ERROR match arms have incompatible types
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1 => |c| c + 1,
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2 => |c| c - 1,
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_ => |c| c - 1
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};
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//~^^^ ERROR match arms have incompatible types
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}
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fn main() { }
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@ -10,20 +10,20 @@ LL | x = |c| c + 1;
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= help: consider boxing your closure and/or using it as a trait object
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error[E0308]: match arms have incompatible types
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--> $DIR/issue-24036.rs:8:13
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--> $DIR/issue-24036.rs:10:14
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LL | let x = match 1usize {
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| _____________^
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LL | | //~^ ERROR match arms have incompatible types
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| _____________-
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LL | | 1 => |c| c + 1,
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| | --------- this is found to be of type `[closure@$DIR/issue-24036.rs:9:14: 9:23]`
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LL | | 2 => |c| c - 1,
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| | --------- match arm with an incompatible type
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| | ^^^^^^^^^ expected closure, found a different closure
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LL | | _ => |c| c - 1
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LL | | };
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| |_____^ expected closure, found a different closure
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| |_____- `match` arms have incompatible types
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= note: expected type `[closure@$DIR/issue-24036.rs:10:14: 10:23]`
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found type `[closure@$DIR/issue-24036.rs:11:14: 11:23]`
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= note: expected type `[closure@$DIR/issue-24036.rs:9:14: 9:23]`
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found type `[closure@$DIR/issue-24036.rs:10:14: 10:23]`
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= note: no two closures, even if identical, have the same type
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= help: consider boxing your closure and/or using it as a trait object
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