diff --git a/src/librustc/infer/error_reporting/mod.rs b/src/librustc/infer/error_reporting/mod.rs index 66e4cd49c807f..82e9a1e3c895b 100644 --- a/src/librustc/infer/error_reporting/mod.rs +++ b/src/librustc/infer/error_reporting/mod.rs @@ -509,22 +509,31 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> { } } } - ObligationCauseCode::MatchExpressionArm { arm_span, source } => match source { + ObligationCauseCode::MatchExpressionArm { + source, + ref prior_arms, + last_ty, + .. + } => match source { hir::MatchSource::IfLetDesugar { .. } => { - let msg = "`if let` arm with an incompatible type"; - if self.tcx.sess.source_map().is_multiline(arm_span) { - err.span_note(arm_span, msg); - } else { - err.span_label(arm_span, msg); - } + let msg = "`if let` arms have incompatible types"; + err.span_label(cause.span, msg); } hir::MatchSource::TryDesugar => {} _ => { - let msg = "match arm with an incompatible type"; - if self.tcx.sess.source_map().is_multiline(arm_span) { - err.span_note(arm_span, msg); - } else { - err.span_label(arm_span, msg); + let msg = "`match` arms have incompatible types"; + err.span_label(cause.span, msg); + if prior_arms.len() <= 4 { + for sp in prior_arms { + err.span_label(*sp, format!( + "this is found to be of type `{}`", + last_ty, + )); + } + } else if let Some(sp) = prior_arms.last() { + err.span_label(*sp, format!( + "this and all prior arms are found to be of type `{}`", last_ty, + )); } } }, diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs index 68383bef37a6a..7fc27ba735e47 100644 --- a/src/librustc/traits/mod.rs +++ b/src/librustc/traits/mod.rs @@ -145,6 +145,7 @@ impl<'tcx> ObligationCause<'tcx> { ObligationCauseCode::StartFunctionType => { tcx.sess.source_map().def_span(self.span) } + ObligationCauseCode::MatchExpressionArm { arm_span, .. } => arm_span, _ => self.span, } } @@ -223,6 +224,8 @@ pub enum ObligationCauseCode<'tcx> { MatchExpressionArm { arm_span: Span, source: hir::MatchSource, + prior_arms: Vec, + last_ty: Ty<'tcx>, }, /// Computing common supertype in the pattern guard for the arms of a match expression diff --git a/src/librustc/traits/structural_impls.rs b/src/librustc/traits/structural_impls.rs index 2f5df022218fe..8bbeec0b8ac2b 100644 --- a/src/librustc/traits/structural_impls.rs +++ b/src/librustc/traits/structural_impls.rs @@ -513,10 +513,21 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> { trait_item_def_id, }), super::ExprAssignable => Some(super::ExprAssignable), - super::MatchExpressionArm { arm_span, source } => Some(super::MatchExpressionArm { + super::MatchExpressionArm { arm_span, - source: source, - }), + source, + ref prior_arms, + last_ty, + } => { + tcx.lift(&last_ty).map(|last_ty| { + super::MatchExpressionArm { + arm_span, + source, + prior_arms: prior_arms.clone(), + last_ty, + } + }) + } super::MatchExpressionArmPattern { span, ty } => { tcx.lift(&ty).map(|ty| super::MatchExpressionArmPattern { span, ty }) } diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs index a90d83f3f8be0..cfc7cedc5e3e5 100644 --- a/src/librustc_typeck/check/_match.rs +++ b/src/librustc_typeck/check/_match.rs @@ -689,6 +689,8 @@ https://doc.rust-lang.org/reference/types.html#trait-objects"); CoerceMany::with_coercion_sites(coerce_first, arms) }; + let mut other_arms = vec![]; // used only for diagnostics + let mut prior_arm_ty = None; for (i, (arm, pats_diverge)) in arms.iter().zip(all_arm_pats_diverge).enumerate() { if let Some(ref g) = arm.guard { self.diverges.set(pats_diverge); @@ -709,17 +711,36 @@ https://doc.rust-lang.org/reference/types.html#trait-objects"); _ => false }; + let arm_span = if let hir::ExprKind::Block(ref blk, _) = arm.body.node { + // Point at the block expr instead of the entire block + blk.expr.as_ref().map(|e| e.span).unwrap_or(arm.body.span) + } else { + arm.body.span + }; if is_if_let_fallback { let cause = self.cause(expr.span, ObligationCauseCode::IfExpressionWithNoElse); assert!(arm_ty.is_unit()); coercion.coerce_forced_unit(self, &cause, &mut |_| (), true); } else { - let cause = self.cause(expr.span, ObligationCauseCode::MatchExpressionArm { - arm_span: arm.body.span, - source: match_src - }); + let cause = if i == 0 { + // The reason for the first arm to fail is not that the match arms diverge, + // but rather that there's a prior obligation that doesn't hold. + self.cause(arm_span, ObligationCauseCode::BlockTailExpression(arm.body.id)) + } else { + self.cause(expr.span, ObligationCauseCode::MatchExpressionArm { + arm_span, + source: match_src, + prior_arms: other_arms.clone(), + last_ty: prior_arm_ty.unwrap(), + }) + }; coercion.coerce(self, &cause, &arm.body, arm_ty); } + other_arms.push(arm_span); + if other_arms.len() > 5 { + other_arms.remove(0); + } + prior_arm_ty = Some(arm_ty); } // We won't diverge unless the discriminant or all arms diverge. diff --git a/src/test/ui/if/if-let-arm-types.rs b/src/test/ui/if/if-let-arm-types.rs index 749c089ae9752..819f5dd1cfc35 100644 --- a/src/test/ui/if/if-let-arm-types.rs +++ b/src/test/ui/if/if-let-arm-types.rs @@ -1,10 +1,11 @@ fn main() { - if let Some(b) = None { //~ ERROR: `if let` arms have incompatible types - //~^ expected (), found integer - //~| expected type `()` - //~| found type `{integer}` + if let Some(b) = None { + //~^ NOTE if let` arms have incompatible types () } else { 1 }; + //~^^ ERROR: `if let` arms have incompatible types + //~| NOTE expected (), found integer + //~| NOTE expected type `()` } diff --git a/src/test/ui/if/if-let-arm-types.stderr b/src/test/ui/if/if-let-arm-types.stderr index fcf9e4695f675..6401a62c06ba2 100644 --- a/src/test/ui/if/if-let-arm-types.stderr +++ b/src/test/ui/if/if-let-arm-types.stderr @@ -1,25 +1,17 @@ error[E0308]: `if let` arms have incompatible types - --> $DIR/if-let-arm-types.rs:2:5 + --> $DIR/if-let-arm-types.rs:6:9 | -LL | / if let Some(b) = None { //~ ERROR: `if let` arms have incompatible types -LL | | //~^ expected (), found integer -LL | | //~| expected type `()` -LL | | //~| found type `{integer}` -... | +LL | / if let Some(b) = None { +LL | | //~^ NOTE if let` arms have incompatible types +LL | | () +LL | | } else { LL | | 1 + | | ^ expected (), found integer LL | | }; - | |_____^ expected (), found integer + | |_____- `if let` arms have incompatible types | = note: expected type `()` found type `{integer}` -note: `if let` arm with an incompatible type - --> $DIR/if-let-arm-types.rs:7:12 - | -LL | } else { - | ____________^ -LL | | 1 -LL | | }; - | |_____^ error: aborting due to previous error diff --git a/src/test/ui/issues/issue-11319.rs b/src/test/ui/issues/issue-11319.rs index ea901205544b6..726c437355e53 100644 --- a/src/test/ui/issues/issue-11319.rs +++ b/src/test/ui/issues/issue-11319.rs @@ -1,12 +1,14 @@ fn main() { match Some(10) { - //~^ ERROR match arms have incompatible types - //~| expected type `bool` - //~| found type `()` - //~| expected bool, found () + //~^ NOTE `match` arms have incompatible types Some(5) => false, + //~^ NOTE this is found to be of type `bool` Some(2) => true, + //~^ NOTE this is found to be of type `bool` None => (), + //~^ ERROR match arms have incompatible types + //~| NOTE expected bool, found () + //~| NOTE expected type `bool` _ => true } } diff --git a/src/test/ui/issues/issue-11319.stderr b/src/test/ui/issues/issue-11319.stderr index 44d63ba3e6879..10db477b8ca7b 100644 --- a/src/test/ui/issues/issue-11319.stderr +++ b/src/test/ui/issues/issue-11319.stderr @@ -1,16 +1,20 @@ error[E0308]: match arms have incompatible types - --> $DIR/issue-11319.rs:2:5 + --> $DIR/issue-11319.rs:8:20 | LL | / match Some(10) { -LL | | //~^ ERROR match arms have incompatible types -LL | | //~| expected type `bool` -LL | | //~| found type `()` -... | +LL | | //~^ NOTE `match` arms have incompatible types +LL | | Some(5) => false, + | | ----- this is found to be of type `bool` +LL | | //~^ NOTE this is found to be of type `bool` +LL | | Some(2) => true, + | | ---- this is found to be of type `bool` +LL | | //~^ NOTE this is found to be of type `bool` LL | | None => (), - | | -- match arm with an incompatible type + | | ^^ expected bool, found () +... | LL | | _ => true LL | | } - | |_____^ expected bool, found () + | |_____- `match` arms have incompatible types | = note: expected type `bool` found type `()` diff --git a/src/test/ui/issues/issue-17728.rs b/src/test/ui/issues/issue-17728.rs index 0f13ae3304d6c..15cea1d609d53 100644 --- a/src/test/ui/issues/issue-17728.rs +++ b/src/test/ui/issues/issue-17728.rs @@ -97,7 +97,7 @@ impl Debug for Player { } fn str_to_direction(to_parse: &str) -> RoomDirection { - match to_parse { //~ ERROR match arms have incompatible types + match to_parse { "w" | "west" => RoomDirection::West, "e" | "east" => RoomDirection::East, "n" | "north" => RoomDirection::North, @@ -108,6 +108,7 @@ fn str_to_direction(to_parse: &str) -> RoomDirection { "down" => RoomDirection::Down, _ => None } + //~^^ ERROR match arms have incompatible types } fn main() { diff --git a/src/test/ui/issues/issue-17728.stderr b/src/test/ui/issues/issue-17728.stderr index 355868f05690f..2c2efad19f569 100644 --- a/src/test/ui/issues/issue-17728.stderr +++ b/src/test/ui/issues/issue-17728.stderr @@ -10,17 +10,19 @@ LL | Some(entry) => Ok(entry), | ^^^^^^^^^ ...but data from `room` is returned here error[E0308]: match arms have incompatible types - --> $DIR/issue-17728.rs:100:5 + --> $DIR/issue-17728.rs:109:14 | -LL | / match to_parse { //~ ERROR match arms have incompatible types +LL | / match to_parse { LL | | "w" | "west" => RoomDirection::West, LL | | "e" | "east" => RoomDirection::East, LL | | "n" | "north" => RoomDirection::North, ... | +LL | | "down" => RoomDirection::Down, + | | ------------------- this and all prior arms are found to be of type `RoomDirection` LL | | _ => None - | | ---- match arm with an incompatible type + | | ^^^^ expected enum `RoomDirection`, found enum `std::option::Option` LL | | } - | |_____^ expected enum `RoomDirection`, found enum `std::option::Option` + | |_____- `match` arms have incompatible types | = note: expected type `RoomDirection` found type `std::option::Option<_>` diff --git a/src/test/ui/issues/issue-24036.rs b/src/test/ui/issues/issue-24036.rs index 3642085934abe..2f501b941b5a6 100644 --- a/src/test/ui/issues/issue-24036.rs +++ b/src/test/ui/issues/issue-24036.rs @@ -6,11 +6,11 @@ fn closure_to_loc() { fn closure_from_match() { let x = match 1usize { - //~^ ERROR match arms have incompatible types 1 => |c| c + 1, 2 => |c| c - 1, _ => |c| c - 1 }; + //~^^^ ERROR match arms have incompatible types } fn main() { } diff --git a/src/test/ui/issues/issue-24036.stderr b/src/test/ui/issues/issue-24036.stderr index 9f799c9b45069..fa9935fcf619d 100644 --- a/src/test/ui/issues/issue-24036.stderr +++ b/src/test/ui/issues/issue-24036.stderr @@ -10,20 +10,20 @@ LL | x = |c| c + 1; = help: consider boxing your closure and/or using it as a trait object error[E0308]: match arms have incompatible types - --> $DIR/issue-24036.rs:8:13 + --> $DIR/issue-24036.rs:10:14 | LL | let x = match 1usize { - | _____________^ -LL | | //~^ ERROR match arms have incompatible types + | _____________- LL | | 1 => |c| c + 1, + | | --------- this is found to be of type `[closure@$DIR/issue-24036.rs:9:14: 9:23]` LL | | 2 => |c| c - 1, - | | --------- match arm with an incompatible type + | | ^^^^^^^^^ expected closure, found a different closure LL | | _ => |c| c - 1 LL | | }; - | |_____^ expected closure, found a different closure + | |_____- `match` arms have incompatible types | - = note: expected type `[closure@$DIR/issue-24036.rs:10:14: 10:23]` - found type `[closure@$DIR/issue-24036.rs:11:14: 11:23]` + = note: expected type `[closure@$DIR/issue-24036.rs:9:14: 9:23]` + found type `[closure@$DIR/issue-24036.rs:10:14: 10:23]` = note: no two closures, even if identical, have the same type = help: consider boxing your closure and/or using it as a trait object diff --git a/src/test/ui/match/match-type-err-first-arm.rs b/src/test/ui/match/match-type-err-first-arm.rs new file mode 100644 index 0000000000000..b4b84ef8f1cec --- /dev/null +++ b/src/test/ui/match/match-type-err-first-arm.rs @@ -0,0 +1,45 @@ +fn main() { + let _ = test_func1(1); + let _ = test_func2(1); +} + +fn test_func1(n: i32) -> i32 { + //~^ NOTE expected `i32` because of return type + match n { + 12 => 'b', + //~^ ERROR mismatched types + //~| NOTE expected i32, found char + _ => 42, + } +} + +fn test_func2(n: i32) -> i32 { + let x = match n { + //~^ NOTE `match` arms have incompatible types + 12 => 'b', + //~^ NOTE this is found to be of type `char` + _ => 42, + //~^ ERROR match arms have incompatible types + //~| NOTE expected char, found integer + //~| NOTE expected type `char` + }; + x +} + +fn test_func3(n: i32) -> i32 { + let x = match n { + //~^ NOTE `match` arms have incompatible types + 1 => 'b', + 2 => 'b', + 3 => 'b', + 4 => 'b', + 5 => 'b', + 6 => 'b', + //~^ NOTE this and all prior arms are found to be of type `char` + _ => 42, + //~^ ERROR match arms have incompatible types + //~| NOTE expected char, found integer + //~| NOTE expected type `char` + }; + x +} diff --git a/src/test/ui/match/match-type-err-first-arm.stderr b/src/test/ui/match/match-type-err-first-arm.stderr new file mode 100644 index 0000000000000..db8bef8dc7755 --- /dev/null +++ b/src/test/ui/match/match-type-err-first-arm.stderr @@ -0,0 +1,53 @@ +error[E0308]: mismatched types + --> $DIR/match-type-err-first-arm.rs:9:15 + | +LL | fn test_func1(n: i32) -> i32 { + | --- expected `i32` because of return type +... +LL | 12 => 'b', + | ^^^ expected i32, found char + +error[E0308]: match arms have incompatible types + --> $DIR/match-type-err-first-arm.rs:21:14 + | +LL | let x = match n { + | _____________- +LL | | //~^ NOTE `match` arms have incompatible types +LL | | 12 => 'b', + | | --- this is found to be of type `char` +LL | | //~^ NOTE this is found to be of type `char` +LL | | _ => 42, + | | ^^ expected char, found integer +... | +LL | | //~| NOTE expected type `char` +LL | | }; + | |_____- `match` arms have incompatible types + | + = note: expected type `char` + found type `{integer}` + +error[E0308]: match arms have incompatible types + --> $DIR/match-type-err-first-arm.rs:39:14 + | +LL | let x = match n { + | _____________- +LL | | //~^ NOTE `match` arms have incompatible types +LL | | 1 => 'b', +LL | | 2 => 'b', +... | +LL | | 6 => 'b', + | | --- this and all prior arms are found to be of type `char` +LL | | //~^ NOTE this and all prior arms are found to be of type `char` +LL | | _ => 42, + | | ^^ expected char, found integer +... | +LL | | //~| NOTE expected type `char` +LL | | }; + | |_____- `match` arms have incompatible types + | + = note: expected type `char` + found type `{integer}` + +error: aborting due to 3 previous errors + +For more information about this error, try `rustc --explain E0308`.