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Rollup merge of #92918 - compiler-errors:gat-expr-lifetime-elision, r=jackh726
Allow eliding GATs in expression position Thoughts on whether this is worthwhile? Fixes #92836 r? ``@jackh726``
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commit
55d5513662
@ -445,7 +445,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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let named_type_param_count =
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param_counts.types - has_self as usize - synth_type_param_count;
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let infer_lifetimes =
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gen_pos != GenericArgPosition::Type && !gen_args.has_lifetime_params();
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(gen_pos != GenericArgPosition::Type || infer_args) && !gen_args.has_lifetime_params();
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if gen_pos != GenericArgPosition::Type && !gen_args.bindings.is_empty() {
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Self::prohibit_assoc_ty_binding(tcx, gen_args.bindings[0].span);
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@ -482,7 +482,20 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
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) -> subst::GenericArg<'tcx> {
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let tcx = self.astconv.tcx();
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match param.kind {
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GenericParamDefKind::Lifetime => tcx.lifetimes.re_static.into(),
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GenericParamDefKind::Lifetime => self
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.astconv
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.re_infer(Some(param), self.span)
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.unwrap_or_else(|| {
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debug!(?param, "unelided lifetime in signature");
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// This indicates an illegal lifetime in a non-assoc-trait position
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tcx.sess.delay_span_bug(self.span, "unelided lifetime in signature");
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// Supply some dummy value. We don't have an
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// `re_error`, annoyingly, so use `'static`.
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tcx.lifetimes.re_static
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})
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.into(),
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GenericParamDefKind::Type { has_default, .. } => {
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if !infer_args && has_default {
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// No type parameter provided, but a default exists.
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@ -0,0 +1,38 @@
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#![feature(generic_associated_types)]
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#![allow(unused)]
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pub trait Trait {
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type Assoc<'a> where Self: 'a;
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fn f(&self) -> Self::Assoc<'_>;
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// Disallow elision in return position, for now
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fn g(&self) -> Self::Assoc;
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//~^ ERROR missing generics for associated type `Trait::Assoc`
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}
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pub struct Struct {
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item: f32
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}
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pub struct GenericStruct<'a> {
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ref_item: &'a f32
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}
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impl Trait for Struct {
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type Assoc<'a> = GenericStruct<'a>;
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fn f(&self) -> Self::Assoc<'_> {
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Self::Assoc {
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ref_item: &self.item
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}
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}
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// Disallow elision in return position, for now
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fn g(&self) -> Self::Assoc {
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//~^ ERROR missing generics for associated type `Trait::Assoc`
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todo!()
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}
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}
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fn main() {}
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@ -0,0 +1,35 @@
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error[E0107]: missing generics for associated type `Trait::Assoc`
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--> $DIR/elided-in-expr-position.rs:10:26
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LL | fn g(&self) -> Self::Assoc;
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| ^^^^^ expected 1 lifetime argument
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note: associated type defined here, with 1 lifetime parameter: `'a`
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--> $DIR/elided-in-expr-position.rs:5:10
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LL | type Assoc<'a> where Self: 'a;
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| ^^^^^ --
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help: add missing lifetime argument
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LL | fn g(&self) -> Self::Assoc<'_>;
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| ~~~~~~~~~
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error[E0107]: missing generics for associated type `Trait::Assoc`
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--> $DIR/elided-in-expr-position.rs:32:26
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LL | fn g(&self) -> Self::Assoc {
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| ^^^^^ expected 1 lifetime argument
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note: associated type defined here, with 1 lifetime parameter: `'a`
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--> $DIR/elided-in-expr-position.rs:5:10
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LL | type Assoc<'a> where Self: 'a;
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| ^^^^^ --
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help: add missing lifetime argument
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LL | fn g(&self) -> Self::Assoc<'_> {
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| ~~~~~~~~~
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0107`.
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