Forbid recursive impl trait #56074

matthewjasper · 2018-11-19T19:45:57Z

There is no type T, such that T = [T; 2], but impl Trait could sometimes
be to circumvented this.

This patch makes it a hard error for an opaque type to resolve to such a
"type". Before this can be merged it needs

A better error message - it's good enough for now.
A crater run (?) to see if this any real-world code

closes #47659

rust-highfive · 2018-11-19T19:46:01Z

r? @zackmdavis

(rust_highfive has picked a reviewer for you, use r? to override)

cramertj · 2018-11-20T02:20:21Z

cc #47659

zackmdavis · 2018-11-22T01:08:39Z

src/librustc_typeck/check/mod.rs

+    span: Span,
+) {
+    if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id, substs) {
+        let mut err = tcx.sess.struct_span_err(span, "recursive opaque type");


Maybe this deserves a dedicated E0XXX error code? (which would be defined in librustc_typeck/diagnostics.rs)

zackmdavis · 2018-11-22T01:09:54Z

@bors try

bors · 2018-11-22T01:10:10Z

⌛ Trying commit cdf5394 with merge db42d4d...

…try> Forbid recursive impl trait There is no type T, such that `T = [T; 2]`, but impl Trait could sometimes be to circumvented this. This patch makes it a hard error for an opaque type to resolve to such a "type". Before this can be merged it needs - [ ] A better error message - [ ] A crater run (?) to see if this any real-world code

bors · 2018-11-22T03:23:42Z

☀️ Test successful - status-travis
State: approved= try=True

matthewjasper · 2018-11-26T22:25:01Z

Can I have a crater run @rust-lang/infra?

pietroalbini · 2018-11-27T08:36:47Z

@craterbot run start=master#0b9f19dff1347e29bf4362ab5a8fab84b43023b5 end=try#db42d4dad33013eba11ef37342ad9f614e5652b8 mode=check-only

craterbot · 2018-11-27T08:36:49Z

👌 Experiment pr-56074 created and queued.
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2018-11-27T15:49:55Z

🚧 Experiment pr-56074 is now running on agent aws-1.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

craterbot · 2018-11-29T05:45:45Z

🎉 Experiment pr-56074 is completed!
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

pietroalbini · 2018-11-29T14:35:50Z

Only one regression, ThatsGobbles/taggu-rust:

Nov 28 10:49:30.564 INFO [stderr] error: recursive opaque type
Nov 28 10:49:30.564 INFO [stderr]    --> src/metadata/mod.rs:149:63
Nov 28 10:49:30.564 INFO [stderr]     |
Nov 28 10:49:30.564 INFO [stderr] 149 |     pub fn iter_over<'a>(&'a self, mis: MappingIterScheme) -> impl Iterator<Item = &'a String> {
Nov 28 10:49:30.564 INFO [stderr]     |                                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ resolves to self-referential type
Nov 28 10:49:30.564 INFO [stderr]     |
Nov 28 10:49:30.564 INFO [stderr]     = note: resolved type is `generator::GenConverter::gen_to_iter::It<[generator@src/metadata/mod.rs:150:23: 184:10 self:&'a metadata::MetaValue, mis:metadata::MappingIterScheme for<'r, 's, 't0, 't1, 't2, 't3, 't4, 't5, 't6, 't7, 't8, 't9, 't10, 't11, 't12, 't13, 't14, 't15, 't16, 't17, 't18, 't19, 't20, 't21, 't22, 't23, 't24, 't25, 't26, 't27, 't28, 't29, 't30, 't31, 't32, 't33, 't34, 't35> {&'r metadata::MetaValue, metadata::MetaValue, &'s std::string::String, (), &'t0 std::vec::Vec<metadata::MetaValue>, fn(&'t1 std::vec::Vec<metadata::MetaValue>) -> <&'t1 std::vec::Vec<metadata::MetaValue> as std::iter::IntoIterator>::IntoIter {<&'t1 std::vec::Vec<metadata::MetaValue> as std::iter::IntoIterator>::into_iter}, std::slice::Iter<'t2, metadata::MetaValue>, std::slice::Iter<'t3, metadata::MetaValue>, &'t4 metadata::MetaValue, &'t5 metadata::MetaValue, fn(std::boxed::Box<impl std::iter::Iterator>) -> <std::boxed::Box<impl std::iter::Iterator> as std::iter::IntoIterator>::IntoIter {<std::boxed::Box<impl std::iter::Iterator> as std::iter::IntoIterator>::into_iter}, fn(impl std::iter::Iterator) -> std::boxed::Box<impl std::iter::Iterator> {<std::boxed::Box<T>><impl std::iter::Iterator>::new}, &'t8 metadata::MetaValue, metadata::MappingIterScheme, impl std::iter::Iterator, std::boxed::Box<impl std::iter::Iterator>, &'t11 std::string::String, &'t12 std::string::String, std::string::String, &'t13 std::string::String, &'t14 std::collections::BTreeMap<metadata::MetaKey, metadata::MetaValue>, fn(&'t15 std::collections::BTreeMap<metadata::MetaKey, metadata::MetaValue>) -> <&'t15 std::collections::BTreeMap<metadata::MetaKey, metadata::MetaValue> as std::iter::IntoIterator>::IntoIter {<&'t15 std::collections::BTreeMap<metadata::MetaKey, metadata::MetaValue> as std::iter::IntoIterator>::into_iter}, std::collections::btree_map::Iter<'t16, metadata::MetaKey, metadata::MetaValue>, std::collections::btree_map::Iter<'t17, metadata::MetaKey, metadata::MetaValue>, (&'t18 metadata::MetaKey, &'t19 metadata::MetaValue), &'t20 metadata::MetaKey, &'t21 metadata::MetaValue, fn(std::boxed::Box<impl std::iter::Iterator>) -> <std::boxed::Box<impl std::iter::Iterator> as std::iter::IntoIterator>::IntoIter {<std::boxed::Box<impl std::iter::Iterator> as std::iter::IntoIterator>::into_iter}, fn(impl std::iter::Iterator) -> std::boxed::Box<impl std::iter::Iterator> {<std::boxed::Box<T>><impl std::iter::Iterator>::new}, metadata::MetaKey, &'t24 metadata::MetaKey, impl std::iter::Iterator, std::boxed::Box<impl std::iter::Iterator>, &'t27 std::string::String, &'t28 std::string::String, fn(std::boxed::Box<impl std::iter::Iterator>) -> <std::boxed::Box<impl std::iter::Iterator> as std::iter::IntoIterator>::IntoIter {<std::boxed::Box<impl std::iter::Iterator> as std::iter::IntoIterator>::into_iter}, fn(impl std::iter::Iterator) -> std::boxed::Box<impl std::iter::Iterator> {<std::boxed::Box<T>><impl std::iter::Iterator>::new}, &'t31 metadata::MetaValue, impl std::iter::Iterator, std::boxed::Box<impl std::iter::Iterator>, &'t34 std::string::String, &'t35 std::string::String}]>`

matthewjasper · 2018-11-29T20:30:31Z

Regression is due to this change. Code in question is:

impl MetaValue {
    pub fn iter_over<'a>(&'a self, mis: MappingIterScheme) -> impl Iterator<Item = &'a String> {
        let closure = move || {
            match *self {
                MetaValue::Nil => {},
                MetaValue::Str(ref s) => { yield s; },
                MetaValue::Seq(ref mvs) => {
                    for mv in mvs {
                        for i in Box::new(mv.iter_over(mis)) {
                            yield i;
                        }
                    }
                },
                MetaValue::Map(ref map) => {
                    for (mk, mv) in map {
                        match mis {
                            MappingIterScheme::Keys | MappingIterScheme::Both => {
                                // This outputs the value of the Nil key first, but only if a BTreeMap is used.
                                for s in Box::new(mk.iter_over()) {
                                    yield s;
                                }
                            },
                            MappingIterScheme::Vals => {},
                        };

                        match mis {
                            MappingIterScheme::Vals | MappingIterScheme::Both => {
                                for s in Box::new(mv.iter_over(mis)) {
                                    yield s;
                                }
                            },
                            MappingIterScheme::Keys => {},
                        };
                    }
                },
            }
        };

        GenConverter::gen_to_iter(closure)
    }
}

Replacing for s in Box::new(mv.iter_over(mis)) { with

let iter = Box::new(mv.iter_over(mis)) as Box<dyn Iterator<Item = &'a String>>;
for s in iter {

fixes this.
using an existential type with a wrapper struct should also work at some point.

So @rust-lang/lang, should this be a future compatibility lint (with what default level)?

eddyb · 2018-12-02T13:50:00Z

r? @nikomatsakis

nikomatsakis

the code is r=me-- haven't looked or thought about crater run results yet

src/librustc/ty/util.rs

src/librustc_typeck/check/mod.rs

src/librustc/ty/util.rs

matthewjasper · 2018-12-15T21:25:20Z

@Centril was a decision reached on whether this should be a future compat lint?

Centril · 2018-12-16T01:55:56Z

I don't recall a decision on that but as there was a regression you might as well do it. An issue filed against the regressed repo would also be nice.

bors · 2019-01-02T16:58:39Z

📌 Commit 671da3d47366a3f79162a8c0a77c3a58f567ced8 has been approved by nikomatsakis

bors · 2019-01-03T09:38:25Z

⌛ Testing commit 671da3d47366a3f79162a8c0a77c3a58f567ced8 with merge 357c9c1522caf3c1ab6c2f4380090650d491db56...

bors · 2019-01-03T10:30:08Z

💔 Test failed - status-travis

rust-highfive · 2019-01-03T10:30:09Z

The job dist-i586-gnu-i586-i686-musl of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:48:39] 
[00:48:39] ---- [ui] ui/impl-trait/infinite-impl-trait-issue-38064.rs stdout ----
[00:48:39] diff of stderr:
[00:48:39] 
[00:48:39] 1 error[E0720]: opaque type expands to a recursive type
[00:48:39] +   --> $DIR/infinite-impl-trait-issue-38064.rs:8:13
[00:48:39] 3    |
[00:48:39] 3    |
[00:48:39] 4 LL | fn foo() -> impl Quux { //~ opaque type expands to a recursive type
[00:48:39] 5    |             ^^^^^^^^^ expands to self-referential type
[00:48:39] 
[00:48:39] 7    = note: expanded type is `foo::Foo<bar::Bar<impl Quux>>`
[00:48:39] 8 
[00:48:39] 9 error[E0720]: opaque type expands to a recursive type
[00:48:39] +   --> $DIR/infinite-impl-trait-issue-38064.rs:14:13
[00:48:39] 11    |
[00:48:39] 11    |
[00:48:39] 12 LL | fn bar() -> impl Quux { //~ opaque type expands to a recursive type
[00:48:39] 13    |             ^^^^^^^^^ expands to self-referential type
[00:48:39] 
[00:48:39] The actual stderr differed from the expected stderr.
[00:48:39] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/impl-trait/infinite-impl-trait-issue-38064/infinite-impl-trait-issue-38064.stderr
[00:48:39] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/impl-trait/infinite-impl-trait-issue-38064/infinite-impl-trait-issue-38064.stderr
[00:48:39] To update references, rerun the tests and pass the `--bless` flag
[00:48:39] To only update this specific test, also pass `--test-args impl-trait/infinite-impl-trait-issue-38064.rs`
[00:48:39] error: 1 errors occurred comparing output.
[00:48:39] status: exit code: 1
[00:48:39] status: exit code: 1
[00:48:39] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs" "--target=i586-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/impl-trait/infinite-impl-trait-issue-38064/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/i586-unknown-linux-gnu/native/rust-test-helpers" "-Clinker=cc" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/impl-trait/infinite-impl-trait-issue-38064/auxiliary" "-A" "unused"
[00:48:39] ------------------------------------------
[00:48:39] 
[00:48:39] ------------------------------------------
[00:48:39] stderr:
[00:48:39] stderr:
[00:48:39] ------------------------------------------
[00:48:39] {"message":"opaque type expands to a recursive type","code":{"code":"E0720","explanation":"\nAn `impl Trait` type expands to a recursive type.\n\nAn `impl Trait` type must be expandable to a concrete type that contains no\n`impl Trait` types. For example the following example tries to create an\n`impl Trait` type `T` that is equal to `[T, T]`:\n\n```compile_fail,E0720\nfn make_recursive_type() -> impl Sized {\n    [make_recursive_type(), make_recursive_type()]\n}\n```\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs","byte_start":154,"byte_end":163,"line_start":8,"line_end":8,"column_start":13,"column_end":22,"is_primary":true,"text":[{"text":"fn foo() -> impl Quux { //~ opaque type expands to a recursive type","highlight_start":13,"highlight_end":22}],"label":"expands to self-referential type","suggested_replacement":null,"suggestion_applicability":null,"expansion":{"span":{"file_name":"/checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs","byte_start":154,"byte_end":163,"line_start":8,"line_end":8,"column_start":13,"column_end":22,"is_primary":false,"text":[{"text":"fn foo() -> impl Quux { //~ opaque type expands to a recursive type","highlight_start":13,"highlight_end":22}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null},"macro_decl_name":"desugaring of `existential type`","def_site_span":{"file_name":"/checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs","byte_start":154,"byte_end":163,"line_start":8,"line_end":8,"column_start":13,"column_end":22,"is_primary":false,"text":[{"text":"fn foo() -> impl Quux { //~ opaque type expands to a recursive type","highlight_start":13,"highlight_end":22}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}}}],"children":[{"message":"expanded type is `foo::Foo<bar::Bar<impl Quux>>`","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"error[E0720]: opaque type expands to a recursive type\n  --> /checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs:8:13\n   |\nLL | fn foo() -> impl Quux { //~ opaque type expands to a recursive type\n   |             ^^^^^^^^^ expands to self-referential type\n   |\n   = note: expanded type is `foo::Foo<bar::Bar<impl Quux>>`\n\n"}
[00:48:39] {"message":"opaque type expands to a recursive type","code":{"code":"E0720","explanation":"\nAn `impl Trait` type expands to a recursive type.\n\nAn `impl Trait` type must be expandable to a concrete type that contains no\n`impl Trait` types. For example the following example tries to create an\n`impl Trait` type `T` that is equal to `[T, T]`:\n\n```compile_fail,E0720\nfn make_recursive_type() -> impl Sized {\n    [make_recursive_type(), make_recursive_type()]\n}\n```\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs","byte_start":293,"byte_end":302,"line_start":14,"line_end":14,"column_start":13,"column_end":22,"is_primary":true,"text":[{"text":"fn bar() -> impl Quux { //~ opaque type expands to a recursive type","highlight_start":13,"highlight_end":22}],"label":"expands to self-referential type","suggested_replacement":null,"suggestion_applicability":null,"expansion":{"span":{"file_name":"/checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs","byte_start":293,"byte_end":302,"line_start":14,"line_end":14,"column_start":13,"column_end":22,"is_primary":false,"text":[{"text":"fn bar() -> impl Quux { //~ opaque type expands to a recursive type","highlight_start":13,"highlight_end":22}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null},"macro_decl_name":"desugaring of `existential type`","def_site_span":{"file_name":"/checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs","byte_start":293,"byte_end":302,"line_start":14,"line_end":14,"column_start":13,"column_end":22,"is_primary":false,"text":[{"text":"fn bar() -> impl Quux { //~ opaque type expands to a recursive type","highlight_start":13,"highlight_end":22}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}}}],"children":[{"message":"expanded type is `bar::Bar<foo::Foo<impl Quux>>`","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"error[E0720]: opaque type expands to a recursive type\n  --> /checkout/src/test/ui/impl-trait/infinite-impl-trait-issue-38064.rs:14:13\n   |\nLL | fn bar() -> impl Quux { //~ opaque type expands to a recursive type\n   |             ^^^^^^^^^ expands to self-referential type\n   |\n   = note: expanded type is `bar::Bar<foo::Foo<impl Quux>>`\n\n"}
[00:48:39] {"message":"aborting due to 2 previous errors","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to 2 previous errors\n\n"}
[00:48:39] {"message":"For more information about this error, try `rustc --explain E0720`.","code":null,"level":"","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0720`.\n"}
[00:48:39] ------------------------------------------
[00:48:39] 
[00:48:39] thread '[ui] ui/impl-trait/infinite-impl-trait-issue-38064.rs' panicked at 'explicit panic', src/tools/compiletest/src/runtest.rs:3245:9
[00:48:39] note: Run with `RUST_BACKTRACE=1` for a backtrace.
---
[00:48:39] 
[00:48:39] thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:495:22
[00:48:39] 
[00:48:39] 
[00:48:39] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/i586-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-i586-unknown-linux-gnu" "--mode" "ui" "--target" "i586-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/checkout/obj/build/x86_64-unknown-linux-gnu/llvm/build/bin/FileCheck" "--linker" "cc" "--host-rustcflags" "-Crpath -O -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Zunstable-options  -Lnative=/checkout/obj/build/i586-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--llvm-version" "8.0.0svn\n" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
[00:48:39] 
[00:48:39] 
[00:48:39] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test --target i586-unknown-linux-gnu,i686-unknown-linux-musl
[00:48:39] Build completed unsuccessfully in 0:46:24
---
travis_time:end:371b0910:start=1546511344068181903,finish=1546511344074849411,duration=6667508
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:0f702870
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:0d5db000
travis_time:start:0d5db000
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:0a1dd79a
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

nikomatsakis · 2019-01-03T17:52:15Z

@matthewjasper looks like this maybe needs a --bless run?

It used to display as just `impl`

matthewjasper · 2019-01-03T21:11:46Z

@bors r=nikomatsakis

bors · 2019-01-03T21:11:47Z

📌 Commit 450c756996340e50a2ed2d385b6e9d2dd6c51f67 has been approved by nikomatsakis

There is no type T, such that `T = [T; 2]`, we should not allow this to be circumvented by impl Trait.

matthewjasper · 2019-01-03T22:16:43Z

@bors r=nikomatsakis

bors · 2019-01-03T22:16:43Z

📌 Commit 65c1f54 has been approved by nikomatsakis

bors · 2019-01-04T14:21:27Z

⌛ Testing commit 65c1f54 with merge ae167c9...

…ikomatsakis Forbid recursive impl trait There is no type T, such that `T = [T; 2]`, but impl Trait could sometimes be to circumvented this. This patch makes it a hard error for an opaque type to resolve to such a "type". Before this can be merged it needs - [x] A better error message - it's good enough for now. - [x] A crater run (?) to see if this any real-world code closes #47659

bors · 2019-01-04T17:01:18Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing ae167c9 to master...

rust-highfive assigned zackmdavis Nov 19, 2018

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Display impl Sized correctly

7ba17aa

It used to display as just `impl`

matthewjasper force-pushed the forbid-recursive-impl-trait branch from 671da3d to 450c756 Compare January 3, 2019 20:49

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 3, 2019

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Forbid impl Trait from referring to unnamable recursive types

65c1f54

There is no type T, such that `T = [T; 2]`, we should not allow this to be circumvented by impl Trait.

matthewjasper force-pushed the forbid-recursive-impl-trait branch from 450c756 to 65c1f54 Compare January 3, 2019 22:16

bors merged commit 65c1f54 into rust-lang:master Jan 4, 2019

estebank mentioned this pull request Jan 4, 2019

For recursive impl trait point at statement that causes the recursion #57341

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matthewjasper deleted the forbid-recursive-impl-trait branch January 5, 2019 20:37

aturon mentioned this pull request Jan 28, 2019

Tracking issue for impl Trait (RFC 1522, RFC 1951, RFC 2071) #34511

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Forbid recursive impl trait #56074

Forbid recursive impl trait #56074

matthewjasper commented Nov 19, 2018 •

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Forbid recursive impl trait #56074

Forbid recursive impl trait #56074

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matthewjasper commented Nov 19, 2018 •

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