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Auto merge of #45069 - sinkuu:tuple_arg, r=nikomatsakis
Better error for missing tuple pattern in args #44150 Before: ``` error[E0593]: closure takes 2 arguments but 1 argument is required --> test.rs:5:40 | 5 | let it = v.into_iter().enumerate().map(|i, x| i); | ^^^ -------- takes 2 arguments | | | expected closure that takes 1 argument ``` After: ``` error[E0593]: closure takes 2 arguments but a 2-tuple is required --> test.rs:5:40 | 5 | let it = v.into_iter().enumerate().map(|i, x| i); | ^^^ ------ takes 2 arguments | | | expected closure that takes a 2-tuple ```
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‎src/librustc/traits/error_reporting.rs‎

Lines changed: 172 additions & 43 deletions
Original file line numberDiff line numberDiff line change
@@ -711,41 +711,105 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
711711
}
712712
}
713713

714-
OutputTypeParameterMismatch(ref expected_trait_ref, ref actual_trait_ref, _) => {
714+
OutputTypeParameterMismatch(ref found_trait_ref, ref expected_trait_ref, _) => {
715+
let found_trait_ref = self.resolve_type_vars_if_possible(&*found_trait_ref);
715716
let expected_trait_ref = self.resolve_type_vars_if_possible(&*expected_trait_ref);
716-
let actual_trait_ref = self.resolve_type_vars_if_possible(&*actual_trait_ref);
717-
if actual_trait_ref.self_ty().references_error() {
717+
if expected_trait_ref.self_ty().references_error() {
718718
return;
719719
}
720-
let expected_trait_ty = expected_trait_ref.self_ty();
721-
let found_span = expected_trait_ty.ty_to_def_id().and_then(|did| {
720+
let found_trait_ty = found_trait_ref.self_ty();
721+
722+
let found_did = found_trait_ty.ty_to_def_id();
723+
let found_span = found_did.and_then(|did| {
722724
self.tcx.hir.span_if_local(did)
723725
});
724726

725-
let self_ty_count =
726-
match expected_trait_ref.skip_binder().substs.type_at(1).sty {
727+
let found_ty_count =
728+
match found_trait_ref.skip_binder().substs.type_at(1).sty {
727729
ty::TyTuple(ref tys, _) => tys.len(),
728730
_ => 1,
729731
};
730-
let arg_ty_count =
731-
match actual_trait_ref.skip_binder().substs.type_at(1).sty {
732-
ty::TyTuple(ref tys, _) => tys.len(),
733-
_ => 1,
732+
let (expected_tys, expected_ty_count) =
733+
match expected_trait_ref.skip_binder().substs.type_at(1).sty {
734+
ty::TyTuple(ref tys, _) =>
735+
(tys.iter().map(|t| &t.sty).collect(), tys.len()),
736+
ref sty => (vec![sty], 1),
734737
};
735-
if self_ty_count == arg_ty_count {
738+
if found_ty_count == expected_ty_count {
736739
self.report_closure_arg_mismatch(span,
737740
found_span,
738-
expected_trait_ref,
739-
actual_trait_ref)
741+
found_trait_ref,
742+
expected_trait_ref)
740743
} else {
741-
// Expected `|| { }`, found `|x, y| { }`
742-
// Expected `fn(x) -> ()`, found `|| { }`
744+
let expected_tuple = if expected_ty_count == 1 {
745+
expected_tys.first().and_then(|t| {
746+
if let &&ty::TyTuple(ref tuptys, _) = t {
747+
Some(tuptys.len())
748+
} else {
749+
None
750+
}
751+
})
752+
} else {
753+
None
754+
};
755+
756+
// FIXME(#44150): Expand this to "N args expected but a N-tuple found."
757+
// Type of the 1st expected argument is somehow provided as type of a
758+
// found one in that case.
759+
//
760+
// ```
761+
// [1i32, 2, 3].sort_by(|(a, b)| ..)
762+
// // ^^^^^^^^
763+
// // expected_trait_ref: std::ops::FnMut<(&i32, &i32)>
764+
// // found_trait_ref: std::ops::FnMut<(&i32,)>
765+
// ```
766+
767+
let (closure_span, closure_args) = found_did
768+
.and_then(|did| self.tcx.hir.get_if_local(did))
769+
.and_then(|node| {
770+
if let hir::map::NodeExpr(
771+
&hir::Expr {
772+
node: hir::ExprClosure(_, ref decl, id, span, _),
773+
..
774+
}) = node
775+
{
776+
let ty_snips = decl.inputs.iter()
777+
.map(|ty| {
778+
self.tcx.sess.codemap().span_to_snippet(ty.span).ok()
779+
.and_then(|snip| {
780+
// filter out dummy spans
781+
if snip == "," || snip == "|" {
782+
None
783+
} else {
784+
Some(snip)
785+
}
786+
})
787+
})
788+
.collect::<Vec<Option<String>>>();
789+
790+
let body = self.tcx.hir.body(id);
791+
let pat_snips = body.arguments.iter()
792+
.map(|arg|
793+
self.tcx.sess.codemap().span_to_snippet(arg.pat.span).ok())
794+
.collect::<Option<Vec<String>>>();
795+
796+
Some((span, pat_snips, ty_snips))
797+
} else {
798+
None
799+
}
800+
})
801+
.map(|(span, pat, ty)| (Some(span), Some((pat, ty))))
802+
.unwrap_or((None, None));
803+
let closure_args = closure_args.and_then(|(pat, ty)| Some((pat?, ty)));
804+
743805
self.report_arg_count_mismatch(
744806
span,
745-
found_span,
746-
arg_ty_count,
747-
self_ty_count,
748-
expected_trait_ty.is_closure()
807+
closure_span.or(found_span),
808+
expected_ty_count,
809+
expected_tuple,
810+
found_ty_count,
811+
closure_args,
812+
found_trait_ty.is_closure()
749813
)
750814
}
751815
}
@@ -767,32 +831,97 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
767831
err.emit();
768832
}
769833

770-
fn report_arg_count_mismatch(&self,
771-
span: Span,
772-
found_span: Option<Span>,
773-
expected: usize,
774-
found: usize,
775-
is_closure: bool)
776-
-> DiagnosticBuilder<'tcx>
777-
{
834+
fn report_arg_count_mismatch(
835+
&self,
836+
span: Span,
837+
found_span: Option<Span>,
838+
expected: usize,
839+
expected_tuple: Option<usize>,
840+
found: usize,
841+
closure_args: Option<(Vec<String>, Vec<Option<String>>)>,
842+
is_closure: bool
843+
) -> DiagnosticBuilder<'tcx> {
844+
use std::borrow::Cow;
845+
846+
let kind = if is_closure { "closure" } else { "function" };
847+
848+
let args_str = |n, distinct| format!(
849+
"{} {}argument{}",
850+
n,
851+
if distinct && n >= 2 { "distinct " } else { "" },
852+
if n == 1 { "" } else { "s" },
853+
);
854+
855+
let expected_str = if let Some(n) = expected_tuple {
856+
assert!(expected == 1);
857+
if closure_args.as_ref().map(|&(ref pats, _)| pats.len()) == Some(n) {
858+
Cow::from("a single tuple as argument")
859+
} else {
860+
// be verbose when numbers differ
861+
Cow::from(format!("a single {}-tuple as argument", n))
862+
}
863+
} else {
864+
Cow::from(args_str(expected, false))
865+
};
866+
867+
let found_str = if expected_tuple.is_some() {
868+
args_str(found, true)
869+
} else {
870+
args_str(found, false)
871+
};
872+
873+
778874
let mut err = struct_span_err!(self.tcx.sess, span, E0593,
779-
"{} takes {} argument{} but {} argument{} {} required",
780-
if is_closure { "closure" } else { "function" },
781-
found,
782-
if found == 1 { "" } else { "s" },
783-
expected,
784-
if expected == 1 { "" } else { "s" },
785-
if expected == 1 { "is" } else { "are" });
786-
787-
err.span_label(span, format!("expected {} that takes {} argument{}",
788-
if is_closure { "closure" } else { "function" },
789-
expected,
790-
if expected == 1 { "" } else { "s" }));
875+
"{} is expected to take {}, but it takes {}",
876+
kind,
877+
expected_str,
878+
found_str,
879+
);
880+
881+
err.span_label(
882+
span,
883+
format!(
884+
"expected {} that takes {}",
885+
kind,
886+
expected_str,
887+
)
888+
);
889+
791890
if let Some(span) = found_span {
792-
err.span_label(span, format!("takes {} argument{}",
793-
found,
794-
if found == 1 { "" } else { "s" }));
891+
if let (Some(expected_tuple), Some((pats, tys))) = (expected_tuple, closure_args) {
892+
if expected_tuple != found || pats.len() != found {
893+
err.span_label(span, format!("takes {}", found_str));
894+
} else {
895+
let sugg = format!(
896+
"|({}){}|",
897+
pats.join(", "),
898+
899+
// add type annotations if available
900+
if tys.iter().any(|ty| ty.is_some()) {
901+
Cow::from(format!(
902+
": ({})",
903+
tys.into_iter().map(|ty| if let Some(ty) = ty {
904+
ty
905+
} else {
906+
"_".to_string()
907+
}).collect::<Vec<String>>().join(", ")
908+
))
909+
} else {
910+
Cow::from("")
911+
},
912+
);
913+
914+
err.span_suggestion(
915+
span,
916+
"consider changing the closure to accept a tuple",
917+
sugg
918+
);
919+
}
920+
} else {
921+
err.span_label(span, format!("takes {}", found_str));
922+
}
795923
}
924+
796925
err
797926
}
798927

‎src/test/ui/mismatched_types/closure-arg-count.rs‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -16,4 +16,8 @@ fn main() {
1616
[1, 2, 3].sort_by(|tuple| panic!());
1717
[1, 2, 3].sort_by(|(tuple, tuple2)| panic!());
1818
f(|| panic!());
19+
20+
let _it = vec![1, 2, 3].into_iter().enumerate().map(|i, x| i);
21+
let _it = vec![1, 2, 3].into_iter().enumerate().map(|i: usize, x| i);
22+
let _it = vec![1, 2, 3].into_iter().enumerate().map(|i, x, y| i);
1923
}

‎src/test/ui/mismatched_types/closure-arg-count.stderr‎

Lines changed: 33 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1,16 +1,16 @@
1-
error[E0593]: closure takes 0 arguments but 2 arguments are required
1+
error[E0593]: closure is expected to take 2 arguments, but it takes 0 arguments
22
--> $DIR/closure-arg-count.rs:15:15
33
|
44
15 | [1, 2, 3].sort_by(|| panic!());
5-
| ^^^^^^^ ----------- takes 0 arguments
5+
| ^^^^^^^ -- takes 0 arguments
66
| |
77
| expected closure that takes 2 arguments
88

9-
error[E0593]: closure takes 1 argument but 2 arguments are required
9+
error[E0593]: closure is expected to take 2 arguments, but it takes 1 argument
1010
--> $DIR/closure-arg-count.rs:16:15
1111
|
1212
16 | [1, 2, 3].sort_by(|tuple| panic!());
13-
| ^^^^^^^ ---------------- takes 1 argument
13+
| ^^^^^^^ ------- takes 1 argument
1414
| |
1515
| expected closure that takes 2 arguments
1616

@@ -23,23 +23,47 @@ error[E0308]: mismatched types
2323
= note: expected type `&{integer}`
2424
found type `(_, _)`
2525

26-
error[E0593]: closure takes 1 argument but 2 arguments are required
26+
error[E0593]: closure is expected to take 2 arguments, but it takes 1 argument
2727
--> $DIR/closure-arg-count.rs:17:15
2828
|
2929
17 | [1, 2, 3].sort_by(|(tuple, tuple2)| panic!());
30-
| ^^^^^^^ -------------------------- takes 1 argument
30+
| ^^^^^^^ ----------------- takes 1 argument
3131
| |
3232
| expected closure that takes 2 arguments
3333

34-
error[E0593]: closure takes 0 arguments but 1 argument is required
34+
error[E0593]: closure is expected to take 1 argument, but it takes 0 arguments
3535
--> $DIR/closure-arg-count.rs:18:5
3636
|
3737
18 | f(|| panic!());
38-
| ^ ----------- takes 0 arguments
38+
| ^ -- takes 0 arguments
3939
| |
4040
| expected closure that takes 1 argument
4141
|
4242
= note: required by `f`
4343

44-
error: aborting due to 5 previous errors
44+
error[E0593]: closure is expected to take a single tuple as argument, but it takes 2 distinct arguments
45+
--> $DIR/closure-arg-count.rs:20:53
46+
|
47+
20 | let _it = vec![1, 2, 3].into_iter().enumerate().map(|i, x| i);
48+
| ^^^ ------ help: consider changing the closure to accept a tuple: `|(i, x)|`
49+
| |
50+
| expected closure that takes a single tuple as argument
51+
52+
error[E0593]: closure is expected to take a single tuple as argument, but it takes 2 distinct arguments
53+
--> $DIR/closure-arg-count.rs:21:53
54+
|
55+
21 | let _it = vec![1, 2, 3].into_iter().enumerate().map(|i: usize, x| i);
56+
| ^^^ ------------- help: consider changing the closure to accept a tuple: `|(i, x): (usize, _)|`
57+
| |
58+
| expected closure that takes a single tuple as argument
59+
60+
error[E0593]: closure is expected to take a single 2-tuple as argument, but it takes 3 distinct arguments
61+
--> $DIR/closure-arg-count.rs:22:53
62+
|
63+
22 | let _it = vec![1, 2, 3].into_iter().enumerate().map(|i, x, y| i);
64+
| ^^^ --------- takes 3 distinct arguments
65+
| |
66+
| expected closure that takes a single 2-tuple as argument
67+
68+
error: aborting due to 8 previous errors
4569

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