librustc: Properly compare implementation method type parameter bounds
with the corresponding trait parameter bounds. This is a version of the patch in PR #12611 by Florian Hahn, modified to address Niko's feedback. It does not address the issue of duplicate type parameter bounds, nor does it address the issue of implementation-defined methods that contain *fewer* bounds than the trait, because Niko's review indicates that this should not be necessary (and indeed I believe it is not). A test has been added to ensure that this works. This will break code like: trait Foo { fn bar<T:Baz>(); } impl Foo for Boo { fn bar<T:Baz + Quux>() { ... } // ^~~~ ERROR } This will be rejected because the implementation requires *more* bounds than the trait. It can be fixed by either adding the missing bound to the trait: trait Foo { fn bar<T:Baz + Quux>(); // ^~~~ } impl Foo for Boo { fn bar<T:Baz + Quux>() { ... } // OK } Or by removing the bound from the impl: trait Foo { fn bar<T:Baz>(); } impl Foo for Boo { fn bar<T:Baz>() { ... } // OK // ^ remove Quux } This patch imports the relevant tests from #2687, as well as the test case in #5886, which is fixed as well by this patch. Closes #2687. Closes #5886. [breaking-change]
This commit is contained in:
Patrick Walton
parent
380657557c
commit
e56dbad9f7
@ -920,49 +920,6 @@ fn compare_impl_method(tcx: &ty::ctxt,
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let it = trait_m.generics.types.get_vec(subst::FnSpace).iter()
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.zip(impl_m.generics.types.get_vec(subst::FnSpace).iter());
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for (i, (trait_param_def, impl_param_def)) in it.enumerate() {
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// Check that the impl does not require any builtin-bounds
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// that the trait does not guarantee:
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let extra_bounds =
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impl_param_def.bounds.builtin_bounds -
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trait_param_def.bounds.builtin_bounds;
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if !extra_bounds.is_empty() {
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tcx.sess.span_err(
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impl_m_span,
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format!("in method `{}`, \
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type parameter {} requires `{}`, \
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which is not required by \
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the corresponding type parameter \
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in the trait declaration",
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token::get_ident(trait_m.ident),
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i,
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extra_bounds.user_string(tcx)).as_slice());
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return;
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}
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// FIXME(#2687)---we should be checking that the bounds of the
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// trait imply the bounds of the subtype, but it appears we
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// are...not checking this.
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if impl_param_def.bounds.trait_bounds.len() !=
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trait_param_def.bounds.trait_bounds.len()
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{
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let found = impl_param_def.bounds.trait_bounds.len();
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let expected = trait_param_def.bounds.trait_bounds.len();
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tcx.sess.span_err(
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impl_m_span,
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format!("in method `{}`, type parameter {} has {} trait \
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bound{}, but the corresponding type parameter in \
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the trait declaration has {} trait bound{}",
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token::get_ident(trait_m.ident),
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i,
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found,
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if found == 1 {""} else {"s"},
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expected,
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if expected == 1 {""} else {"s"}).as_slice());
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return;
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}
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}
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// This code is best explained by example. Consider a trait:
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//
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// trait Trait<T> {
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@ -1037,6 +994,70 @@ fn compare_impl_method(tcx: &ty::ctxt,
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let trait_fty = ty::mk_bare_fn(tcx, trait_m.fty.clone());
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let trait_fty = trait_fty.subst(tcx, &trait_to_skol_substs);
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// Check bounds.
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for (i, (trait_param_def, impl_param_def)) in it.enumerate() {
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// Check that the impl does not require any builtin-bounds
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// that the trait does not guarantee:
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let extra_bounds =
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impl_param_def.bounds.builtin_bounds -
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trait_param_def.bounds.builtin_bounds;
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if !extra_bounds.is_empty() {
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tcx.sess.span_err(
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impl_m_span,
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format!("in method `{}`, \
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type parameter {} requires `{}`, \
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which is not required by \
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the corresponding type parameter \
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in the trait declaration",
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token::get_ident(trait_m.ident),
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i,
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extra_bounds.user_string(tcx)).as_slice());
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return;
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}
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// Check that the trait bounds of the trait imply the bounds of its
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// implementation.
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//
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// FIXME(pcwalton): We could be laxer here regarding sub- and super-
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// traits, but I doubt that'll be wanted often, so meh.
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for impl_trait_bound in impl_param_def.bounds.trait_bounds.iter() {
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let impl_trait_bound =
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impl_trait_bound.subst(tcx, &impl_to_skol_substs);
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let mut ok = false;
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for trait_bound in trait_param_def.bounds.trait_bounds.iter() {
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let trait_bound =
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trait_bound.subst(tcx, &trait_to_skol_substs);
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let infcx = infer::new_infer_ctxt(tcx);
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match infer::mk_sub_trait_refs(&infcx,
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true,
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infer::Misc(impl_m_span),
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trait_bound,
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impl_trait_bound.clone()) {
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Ok(_) => {
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ok = true;
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break
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}
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Err(_) => continue,
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}
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}
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if !ok {
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tcx.sess.span_err(impl_m_span,
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format!("in method `{}`, type parameter {} \
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requires bound `{}`, which is not \
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required by the corresponding \
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type parameter in the trait \
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declaration",
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token::get_ident(trait_m.ident),
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i,
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ppaux::trait_ref_to_str(
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tcx,
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&*impl_trait_bound)).as_slice())
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}
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}
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}
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// Check the impl method type IM is a subtype of the trait method
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// type TM. To see why this makes sense, think of a vtable. The
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// expected type of the function pointers in the vtable is the
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78
src/test/compile-fail/trait-bounds-impl-comparison-1.rs
Normal file
78
src/test/compile-fail/trait-bounds-impl-comparison-1.rs
Normal file
@ -0,0 +1,78 @@
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//
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// Make sure rustc checks the type parameter bounds in implementations of traits,
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// see #2687
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trait A {}
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trait B: A {}
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trait C: A {}
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trait Foo {
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fn test_error1_fn<T: Eq>(&self);
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fn test_error2_fn<T: Eq + Ord>(&self);
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fn test_error3_fn<T: Eq + Ord>(&self);
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fn test3_fn<T: Eq + Ord>(&self);
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fn test4_fn<T: Eq + Ord>(&self);
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fn test_error5_fn<T: A>(&self);
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fn test6_fn<T: A + Eq>(&self);
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fn test_error7_fn<T: A>(&self);
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fn test_error8_fn<T: B>(&self);
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}
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impl Foo for int {
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// invalid bound for T, was defined as Eq in trait
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fn test_error1_fn<T: Ord>(&self) {}
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//~^ ERROR in method `test_error1_fn`, type parameter 0 requires bound `core::cmp::Ord`
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// invalid bound for T, was defined as Eq + Ord in trait
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fn test_error2_fn<T: Eq + B>(&self) {}
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//~^ ERROR in method `test_error2_fn`, type parameter 0 requires bound `B`
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// invalid bound for T, was defined as Eq + Ord in trait
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fn test_error3_fn<T: B + Eq>(&self) {}
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//~^ ERROR in method `test_error3_fn`, type parameter 0 requires bound `B`
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// multiple bounds, same order as in trait
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fn test3_fn<T: Ord + Eq>(&self) {}
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// multiple bounds, different order as in trait
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fn test4_fn<T: Eq + Ord>(&self) {}
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// parameters in impls must be equal or more general than in the defining trait
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fn test_error5_fn<T: B>(&self) {}
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//~^ ERROR in method `test_error5_fn`, type parameter 0 requires bound `B`
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// bound `std::cmp::Eq` not enforced by this implementation, but this is OK
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fn test6_fn<T: A>(&self) {}
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fn test_error7_fn<T: A + Eq>(&self) {}
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//~^ ERROR in method `test_error7_fn`, type parameter 0 requires bound `core::cmp::Eq`
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fn test_error8_fn<T: C>(&self) {}
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//~^ ERROR in method `test_error8_fn`, type parameter 0 requires bound `C`
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}
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trait Getter<T> { }
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trait Trait {
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fn method<G:Getter<int>>();
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}
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impl Trait for uint {
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fn method<G: Getter<uint>>() {}
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//~^ ERROR in method `method`, type parameter 0 requires bound `Getter<uint>`
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}
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fn main() {}
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33
src/test/compile-fail/trait-bounds-impl-comparison-2.rs
Normal file
33
src/test/compile-fail/trait-bounds-impl-comparison-2.rs
Normal file
@ -0,0 +1,33 @@
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Issue #5886: a complex instance of issue #2687.
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trait Iterator<A> {
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fn next(&mut self) -> Option<A>;
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}
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trait IteratorUtil<A> {
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fn zip<B, U: Iterator<U>>(self, other: U) -> ZipIterator<Self, U>;
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}
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impl<A, T: Iterator<A>> IteratorUtil<A> for T {
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fn zip<B, U: Iterator<B>>(self, other: U) -> ZipIterator<T, U> {
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//~^ ERROR in method `zip`, type parameter 1 requires bound `Iterator<B>`
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ZipIterator{a: self, b: other}
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}
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}
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struct ZipIterator<T, U> {
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a: T, b: U
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}
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fn main() {}
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25
src/test/run-pass/trait-bounds-impl-comparison-duplicates.rs
Normal file
25
src/test/run-pass/trait-bounds-impl-comparison-duplicates.rs
Normal file
@ -0,0 +1,25 @@
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Tests that type parameter bounds on an implementation need not match the
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// trait exactly, as long as the implementation doesn't demand *more* bounds
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// than the trait.
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trait A {
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fn foo<T: Eq + Ord>(&self);
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}
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impl A for int {
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fn foo<T: Ord + Ord>(&self) {}
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}
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fn main() {}
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