Trust signature over return expr for generators.
This commit extends the logic used to determine what the expected signature of a closure is so that it can also determine the expected signature of a generator. This improves a diagnostic where the fn signature was blamed instead of the generator body. It doesn't fix fix the diagnostic for `async fn`.
This commit is contained in:
David Wood
parent
a416a19153
commit
f2919a31c8
5 changed files with 53 additions and 53 deletions
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@ -246,7 +246,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
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}
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/// Given a projection like "<F as Fn(X)>::Result == Y", we can deduce
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/// everything we need to know about a closure.
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/// everything we need to know about a closure or generator.
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///
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/// The `cause_span` should be the span that caused us to
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/// have this expected signature, or `None` if we can't readily
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@ -262,37 +262,50 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
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let trait_ref = projection.to_poly_trait_ref(tcx);
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if tcx.lang_items().fn_trait_kind(trait_ref.def_id()).is_none() {
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let is_fn = tcx.lang_items().fn_trait_kind(trait_ref.def_id()).is_some();
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let gen_trait = tcx.lang_items().gen_trait().unwrap();
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let is_gen = gen_trait == trait_ref.def_id();
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if !is_fn && !is_gen {
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debug!("deduce_sig_from_projection: not fn or generator");
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return None;
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}
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let arg_param_ty = trait_ref.skip_binder().substs.type_at(1);
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let arg_param_ty = self.resolve_type_vars_if_possible(&arg_param_ty);
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debug!(
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"deduce_sig_from_projection: arg_param_ty {:?}",
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arg_param_ty
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);
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if is_gen {
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// Check that we deduce the signature from the `<_ as std::ops::Generator>::Return`
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// associated item and not yield.
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let return_assoc_item = self.tcx.associated_items(gen_trait).nth(1).unwrap().def_id;
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if return_assoc_item != projection.projection_def_id() {
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debug!("deduce_sig_from_projection: not return assoc item of generator");
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return None;
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}
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}
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let input_tys = match arg_param_ty.sty {
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ty::Tuple(tys) => tys.into_iter().map(|k| k.expect_ty()),
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_ => return None,
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let input_tys = if is_fn {
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let arg_param_ty = trait_ref.skip_binder().substs.type_at(1);
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let arg_param_ty = self.resolve_type_vars_if_possible(&arg_param_ty);
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debug!("deduce_sig_from_projection: arg_param_ty={:?}", arg_param_ty);
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match arg_param_ty.sty {
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ty::Tuple(tys) => tys.into_iter().map(|k| k.expect_ty()).collect::<Vec<_>>(),
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_ => return None,
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}
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} else {
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// Generators cannot have explicit arguments.
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vec![]
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};
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let ret_param_ty = projection.skip_binder().ty;
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let ret_param_ty = self.resolve_type_vars_if_possible(&ret_param_ty);
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debug!(
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"deduce_sig_from_projection: ret_param_ty {:?}",
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ret_param_ty
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);
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debug!("deduce_sig_from_projection: ret_param_ty={:?}", ret_param_ty);
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let sig = self.tcx.mk_fn_sig(
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input_tys,
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ret_param_ty,
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input_tys.iter(),
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&ret_param_ty,
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false,
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hir::Unsafety::Normal,
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Abi::Rust,
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);
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debug!("deduce_sig_from_projection: sig {:?}", sig);
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debug!("deduce_sig_from_projection: sig={:?}", sig);
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Some(ExpectedSig { cause_span, sig })
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}
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@ -13,7 +13,7 @@ pub fn want_cyclic_generator_return<T>(_: T)
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fn supply_cyclic_generator_return() {
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want_cyclic_generator_return(|| {
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//~^ ERROR type mismatch
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//~^ ERROR closure/generator type that references itself
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if false { yield None.unwrap(); }
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None.unwrap()
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})
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@ -1,20 +1,17 @@
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error[E0271]: type mismatch resolving `<[generator@$DIR/generator-yielding-or-returning-itself.rs:15:34: 19:6 _] as std::ops::Generator>::Return == [generator@$DIR/generator-yielding-or-returning-itself.rs:15:34: 19:6 _]`
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--> $DIR/generator-yielding-or-returning-itself.rs:15:5
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error[E0644]: closure/generator type that references itself
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--> $DIR/generator-yielding-or-returning-itself.rs:15:34
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LL | want_cyclic_generator_return(|| {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
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LL | want_cyclic_generator_return(|| {
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| __________________________________^
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LL | |
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LL | | if false { yield None.unwrap(); }
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LL | | None.unwrap()
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LL | | })
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| |_____^ cyclic type of infinite size
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= note: closures cannot capture themselves or take themselves as argument;
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this error may be the result of a recent compiler bug-fix,
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see https://github.com/rust-lang/rust/issues/46062 for more details
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note: required by `want_cyclic_generator_return`
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--> $DIR/generator-yielding-or-returning-itself.rs:9:1
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LL | / pub fn want_cyclic_generator_return<T>(_: T)
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LL | | where T: Generator<Yield = (), Return = T>
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LL | | {
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LL | | }
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| |_^
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error[E0271]: type mismatch resolving `<[generator@$DIR/generator-yielding-or-returning-itself.rs:28:33: 32:6 _] as std::ops::Generator>::Yield == [generator@$DIR/generator-yielding-or-returning-itself.rs:28:33: 32:6 _]`
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--> $DIR/generator-yielding-or-returning-itself.rs:28:5
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@ -36,4 +33,5 @@ LL | | }
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0271`.
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Some errors have detailed explanations: E0271, E0644.
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For more information about an error, try `rustc --explain E0271`.
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@ -2,15 +2,15 @@
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use std::ops::Generator;
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fn foo() -> impl Generator<Return = i32> { //~ ERROR type mismatch
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fn foo() -> impl Generator<Return = i32> {
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|| {
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if false {
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return Ok(6);
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return Ok(6); //~ ERROR mismatched types [E0308]
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}
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yield ();
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5 //~ ERROR mismatched types [E0308]
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5
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}
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}
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@ -1,23 +1,12 @@
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error[E0308]: mismatched types
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--> $DIR/type-mismatch-signature-deduction.rs:13:9
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--> $DIR/type-mismatch-signature-deduction.rs:8:20
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LL | 5
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| ^ expected enum `std::result::Result`, found integer
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LL | return Ok(6);
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| ^^^^^ expected i32, found enum `std::result::Result`
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= note: expected type `std::result::Result<{integer}, _>`
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found type `{integer}`
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= note: expected type `i32`
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found type `std::result::Result<{integer}, _>`
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error[E0271]: type mismatch resolving `<[generator@$DIR/type-mismatch-signature-deduction.rs:6:5: 14:6 _] as std::ops::Generator>::Return == i32`
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--> $DIR/type-mismatch-signature-deduction.rs:5:13
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LL | fn foo() -> impl Generator<Return = i32> {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected enum `std::result::Result`, found i32
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= note: expected type `std::result::Result<{integer}, _>`
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found type `i32`
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= note: the return type of a function must have a statically known size
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error: aborting due to previous error
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error: aborting due to 2 previous errors
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Some errors have detailed explanations: E0271, E0308.
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For more information about an error, try `rustc --explain E0271`.
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For more information about this error, try `rustc --explain E0308`.
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