ignore higher-ranked object bound conditions created by WF #59132
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In the `issue-53548` test added in this commit, the `Box<dyn Trait>`
type is expanded to `Box<dyn Trait + 'static>`, but the generator
"witness" that results is `for<'r> { Box<dyn Trait + 'r> }`. The WF
code was encountering an ICE (when debug-assertions were enabled) and
an unexpected compilation error (without debug-asserions) when trying
to process this `'r` region bound. In particular, to be WF, the region
bound must meet the requirements of the trait, and hence we got
`for<'r> { 'r: 'static }`. This would ICE because the `Binder`
constructor we were using was assering that no higher-ranked regions
were involved (because the WF code is supposed to skip those). The
error (if debug-asserions were disabled) came because we obviously
cannot prove that `'r: 'static` for any region `'r`. Pursuant with
our "lazy WF" strategy for higher-ranked regions, the fix is not to
require that `for<'r> { 'r: 'static }` holds (this is also analogous
to what we would do for higher-ranked regions appearing within the
trait in other positions).
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…bound, r=pnkfelix
ignore higher-ranked object bound conditions created by WF
In the `issue-53548` test added in this PR, the `Box<dyn Trait>` type is expanded to `Box<dyn Trait + 'static>`, but the generator "witness" that results is `for<'r> { Box<dyn Trait + 'r> }`. The WF code was encountering an ICE (when debug-assertions were enabled) and an unexpected compilation error (without debug-asserions) when trying to process this `'r` region bound. In particular, to be WF, the region bound must meet the requirements of the trait, and hence we got `for<'r> { 'r: 'static }`. This would ICE because the `Binder` constructor we were using was assering that no higher-ranked regions were involved (because the WF code is supposed to skip those). The error (if debug-asserions were disabled) came because we obviously cannot prove that `'r: 'static` for any region `'r`. Pursuant with
our "lazy WF" strategy for higher-ranked regions, the fix is not to require that `for<'r> { 'r: 'static }` holds (this is also analogous to what we would do for higher-ranked regions appearing within the trait in other positions).
Fixes rust-lang#53548
r? @pnkfelix
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that referenced
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Mar 13, 2019
Rollup of 16 pull requests Successful merges: - #58829 (librustc_interface: Update scoped-tls to 1.0) - #58876 (Parse lifetimes that start with a number and give specific error) - #58908 (Update rand version) - #58998 (Fix documentation of from_ne_bytes and from_le_bytes) - #59056 (Use lifetime contravariance to elide more lifetimes in core+alloc+std) - #59057 (Standardize `Range*` documentation) - #59080 (Fix incorrect links in librustc_codegen_llvm documentation) - #59083 (Fix #54822 and associated faulty tests) - #59093 (Remove precompute_in_scope_traits_hashes) - #59101 (Reduces Code Repetitions like `!n >> amt`) - #59121 (impl FromIterator for Result: Use assert_eq! instead of assert!) - #59124 (Replace assert with assert_eq) - #59129 (Visit impl Trait for dead_code lint) - #59130 (Note that NonNull does not launder shared references for mutation) - #59132 (ignore higher-ranked object bound conditions created by WF) - #59138 (Simplify Iterator::{min, max}) Failed merges: r? @ghost
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In the
issue-53548test added in this PR, theBox<dyn Trait>type is expanded toBox<dyn Trait + 'static>, but the generator "witness" that results isfor<'r> { Box<dyn Trait + 'r> }. The WF code was encountering an ICE (when debug-assertions were enabled) and an unexpected compilation error (without debug-asserions) when trying to process this'rregion bound. In particular, to be WF, the region bound must meet the requirements of the trait, and hence we gotfor<'r> { 'r: 'static }. This would ICE because theBinderconstructor we were using was assering that no higher-ranked regions were involved (because the WF code is supposed to skip those). The error (if debug-asserions were disabled) came because we obviously cannot prove that'r: 'staticfor any region'r. Pursuant withour "lazy WF" strategy for higher-ranked regions, the fix is not to require that
for<'r> { 'r: 'static }holds (this is also analogous to what we would do for higher-ranked regions appearing within the trait in other positions).Fixes #53548
r? @pnkfelix