Auto merge of #65068 - estebank:trait-impl-lt-mismatch, r=nikomatsakis
Custom lifetime error for `impl` item doesn't conform to `trait` Partly addresses #42706, #41343, fix #40900.
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commit
0b7e28a161
10 changed files with 115 additions and 53 deletions
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@ -12,6 +12,7 @@ mod named_anon_conflict;
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mod placeholder_error;
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mod outlives_closure;
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mod static_impl_trait;
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mod trait_impl_difference;
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mod util;
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impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
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@ -73,6 +74,7 @@ impl<'cx, 'tcx> NiceRegionError<'cx, 'tcx> {
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.or_else(|| self.try_report_anon_anon_conflict())
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.or_else(|| self.try_report_outlives_closure())
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.or_else(|| self.try_report_static_impl_trait())
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.or_else(|| self.try_report_impl_not_conforming_to_trait())
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}
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pub fn get_regions(&self) -> (Span, ty::Region<'tcx>, ty::Region<'tcx>) {
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@ -0,0 +1,59 @@
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//! Error Reporting for `impl` items that do not match the obligations from their `trait`.
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use syntax_pos::Span;
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use crate::ty::Ty;
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use crate::infer::{ValuePairs, Subtype};
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use crate::infer::error_reporting::nice_region_error::NiceRegionError;
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use crate::infer::lexical_region_resolve::RegionResolutionError;
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use crate::util::common::ErrorReported;
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use crate::traits::ObligationCauseCode::CompareImplMethodObligation;
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impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
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/// Print the error message for lifetime errors when the `impl` doesn't conform to the `trait`.
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pub(super) fn try_report_impl_not_conforming_to_trait(&self) -> Option<ErrorReported> {
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if let Some(ref error) = self.error {
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debug!("try_report_impl_not_conforming_to_trait {:?}", error);
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if let RegionResolutionError::SubSupConflict(
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_,
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var_origin,
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sub_origin,
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_sub,
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sup_origin,
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_sup,
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) = error.clone() {
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match (&sup_origin, &sub_origin) {
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(&Subtype(ref sup_trace), &Subtype(ref sub_trace)) => {
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if let (
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ValuePairs::Types(sub_expected_found),
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ValuePairs::Types(sup_expected_found),
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CompareImplMethodObligation { trait_item_def_id, .. },
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) = (&sub_trace.values, &sup_trace.values, &sub_trace.cause.code) {
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if sup_expected_found == sub_expected_found {
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self.emit_err(
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var_origin.span(),
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sub_expected_found.expected,
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sub_expected_found.found,
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self.tcx().def_span(*trait_item_def_id),
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);
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return Some(ErrorReported);
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}
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}
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}
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_ => {}
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}
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}
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}
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None
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}
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fn emit_err(&self, sp: Span, expected: Ty<'tcx>, found: Ty<'tcx>, impl_sp: Span) {
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let mut err = self.tcx().sess.struct_span_err(
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sp,
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"`impl` item signature doesn't match `trait` item signature",
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);
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err.note(&format!("expected `{:?}`\n found `{:?}`", expected, found));
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err.span_label(sp, &format!("found {:?}", found));
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err.span_label(impl_sp, &format!("expected {:?}", expected));
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err.emit();
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}
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}
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@ -1,3 +1,5 @@
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// ignore-x86
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// ^ due to stderr output differences
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use std::ops::Deref;
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trait Trait {}
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@ -6,9 +8,9 @@ struct Struct;
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impl Deref for Struct {
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type Target = dyn Trait;
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fn deref(&self) -> &dyn Trait {
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//~^ ERROR `impl` item signature doesn't match `trait` item signature
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unimplemented!();
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}
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}
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//~^^^^ ERROR cannot infer an appropriate lifetime for lifetime parameter
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fn main() {}
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@ -1,21 +1,16 @@
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error[E0495]: cannot infer an appropriate lifetime for lifetime parameter in generic type due to conflicting requirements
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--> $DIR/mismatched_trait_impl-2.rs:8:5
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error: `impl` item signature doesn't match `trait` item signature
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--> $DIR/mismatched_trait_impl-2.rs:10:5
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LL | fn deref(&self) -> &dyn Trait {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ found fn(&Struct) -> &dyn Trait
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::: $SRC_DIR/libcore/ops/deref.rs:LL:COL
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note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the method body at 8:5...
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--> $DIR/mismatched_trait_impl-2.rs:8:5
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LL | fn deref(&self) -> &Self::Target;
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| --------------------------------- expected fn(&Struct) -> &(dyn Trait + 'static)
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LL | / fn deref(&self) -> &dyn Trait {
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LL | | unimplemented!();
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LL | | }
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| |_____^
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= note: ...but the lifetime must also be valid for the static lifetime...
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= note: ...so that the method type is compatible with trait:
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expected fn(&Struct) -> &(dyn Trait + 'static)
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found fn(&Struct) -> &dyn Trait
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= note: expected `fn(&Struct) -> &(dyn Trait + 'static)`
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found `fn(&Struct) -> &dyn Trait`
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0495`.
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@ -1,25 +1,14 @@
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error[E0495]: cannot infer an appropriate lifetime for lifetime parameter 'a in generic type due to conflicting requirements
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error: `impl` item signature doesn't match `trait` item signature
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--> $DIR/mismatched_trait_impl.rs:9:5
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LL | fn foo(&self, x: &'a u32, y: &u32) -> &'a u32;
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| ---------------------------------------------- expected fn(&i32, &'a u32, &u32) -> &'a u32
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...
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LL | fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ found fn(&i32, &u32, &u32) -> &u32
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note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the method body at 9:5...
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--> $DIR/mismatched_trait_impl.rs:9:5
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LL | / fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 {
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LL | | x
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LL | | }
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| |_____^
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note: ...but the lifetime must also be valid for the lifetime `'a` as defined on the method body at 9:32...
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--> $DIR/mismatched_trait_impl.rs:9:32
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LL | fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 {
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| ^^
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= note: ...so that the method type is compatible with trait:
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expected fn(&i32, &'a u32, &u32) -> &'a u32
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found fn(&i32, &u32, &u32) -> &u32
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= note: expected `fn(&i32, &'a u32, &u32) -> &'a u32`
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found `fn(&i32, &u32, &u32) -> &u32`
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0495`.
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@ -6,7 +6,7 @@ trait Get {
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}
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impl Get for i32 {
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fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 { //~ ERROR cannot infer
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fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 { //~ ERROR `impl` item signature doesn't match
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x //~ ERROR lifetime mismatch
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}
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}
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@ -1,24 +1,14 @@
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error[E0495]: cannot infer an appropriate lifetime for lifetime parameter 'a in generic type due to conflicting requirements
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error: `impl` item signature doesn't match `trait` item signature
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--> $DIR/mismatched_trait_impl.rs:9:5
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LL | fn foo(&self, x: &'a u32, y: &u32) -> &'a u32;
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| ---------------------------------------------- expected fn(&i32, &'a u32, &u32) -> &'a u32
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...
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LL | fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ found fn(&i32, &u32, &u32) -> &u32
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note: first, the lifetime cannot outlive the anonymous lifetime #2 defined on the method body at 9:5...
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--> $DIR/mismatched_trait_impl.rs:9:5
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LL | / fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 {
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LL | | x
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LL | | }
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| |_____^
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note: ...but the lifetime must also be valid for the lifetime `'a` as defined on the method body at 9:32...
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--> $DIR/mismatched_trait_impl.rs:9:32
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LL | fn foo(&self, x: &u32, y: &'a u32) -> &'a u32 {
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| ^^
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= note: ...so that the method type is compatible with trait:
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expected fn(&i32, &'a u32, &u32) -> &'a u32
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found fn(&i32, &u32, &u32) -> &u32
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= note: expected `fn(&i32, &'a u32, &u32) -> &'a u32`
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found `fn(&i32, &u32, &u32) -> &u32`
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error[E0623]: lifetime mismatch
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--> $DIR/mismatched_trait_impl.rs:10:9
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@ -32,4 +22,3 @@ LL | x
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0495`.
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@ -0,0 +1,12 @@
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trait Foo {
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fn foo<'a>(x: &i32, y: &'a i32) -> &'a i32;
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}
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impl Foo for () {
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fn foo<'a>(x: &'a i32, y: &'a i32) -> &'a i32 {
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//~^ ERROR `impl` item signature doesn't match `trait` item signature
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if x > y { x } else { y }
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}
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}
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fn main() {}
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@ -0,0 +1,14 @@
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error: `impl` item signature doesn't match `trait` item signature
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--> $DIR/lifetime-mismatch-between-trait-and-impl.rs:6:5
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LL | fn foo<'a>(x: &i32, y: &'a i32) -> &'a i32;
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| ------------------------------------------- expected fn(&i32, &'a i32) -> &'a i32
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...
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LL | fn foo<'a>(x: &'a i32, y: &'a i32) -> &'a i32 {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ found fn(&i32, &i32) -> &i32
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= note: expected `fn(&i32, &'a i32) -> &'a i32`
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found `fn(&i32, &i32) -> &i32`
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error: aborting due to previous error
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@ -52,6 +52,6 @@ impl<One> Drop for V<One,One> { fn drop(&mut self) { } } // REJECT
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//~^ ERROR Implementations of Drop cannot be specialized
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impl<'lw> Drop for W<'lw,'lw> { fn drop(&mut self) { } } // REJECT
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//~^ ERROR cannot infer an appropriate lifetime
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//~^ ERROR cannot infer an appropriate lifetime for lifetime parameter `'lw`
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pub fn main() { }
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