Update Rhs on ShlAssign to default to Self

[npmccallum]

This matches the behavior on ShrAssign and all other *Assign operations.

[BurntSushi]

@rust-lang/libs This seems fine to me if it is consistent with other traits. Are there any backwards compatibility concerns to worry about here? (I don't think so?)

[alexcrichton]

Oh dear this definitely looks like an oversight! I can't think of any back-compat concerns but since this is a widely used trait I think we could benefit from crater

@bors: try

@rust-lang/release could a crater run be scheduled for this PR?

[bors]

⌛ Trying commit 37464a0a7d53cc22b4345d5b8a6773810fc0a38e with merge 4846fb5a35cbaeaa1107a3550cbfde95362b47c3...

[bors]

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

[clarfonthey]

I honestly would have suggested to default to Self for most traits, but I thought that not defaulting for shift ops was intentional. Because at least one of them defaults, I'd make sure we do fix all of them before crater runs.

[npmccallum]

It looks like we aren't missing any other instances of this oversight:

$ grep -R "pub trait .*Rhs" src/
src/libcore/cmp.rs:pub trait PartialEq<Rhs: ?Sized = Self> {
src/libcore/cmp.rs:pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
src/libcore/ops/arith.rs:pub trait AddAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait SubAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait MulAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait DivAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait RemAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitAndAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitOrAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitXorAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait ShlAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait ShrAssign<Rhs=Self> {

For reference, this is before my patch:

$ grep -R "pub trait .*Rhs" src/
src/libcore/cmp.rs:pub trait PartialEq<Rhs: ?Sized = Self> {
src/libcore/cmp.rs:pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
src/libcore/ops/arith.rs:pub trait AddAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait SubAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait MulAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait DivAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait RemAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitAndAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitOrAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitXorAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait ShlAssign<Rhs> {
src/libcore/ops/bit.rs:pub trait ShrAssign<Rhs=Self> {

[leoyvens]

I believe we currently guarantee that adding a default doesn't break anything.

[clarfonthey]

@npmccallum Shl and Shr don't; ShlAssign did for some reason

[npmccallum]

@clarcharr I pushed a new version of the patch which fixes Shl and Shr in addition to ShlAssign. ShrAssign is already correct.

Please also see this related issue: rust-lang/libc#964

[npmccallum]

After the above patches (including libc), we get these results:

$ grep -Ri "pub trait .*Rhs" src/
src/doc/book/first-edition/src/operators-and-overloading.md:pub trait Add<RHS = Self> {
src/doc/rust-by-example/src/generics/phantom/testcase_units.md:pub trait Add<RHS = Self> {
src/libcore/cmp.rs:pub trait PartialEq<Rhs: ?Sized = Self> {
src/libcore/cmp.rs:pub trait PartialOrd<Rhs: ?Sized = Self>: PartialEq<Rhs> {
src/libcore/ops/arith.rs:pub trait Add<RHS=Self> {
src/libcore/ops/arith.rs:pub trait Sub<RHS=Self> {
src/libcore/ops/arith.rs:pub trait Mul<RHS=Self> {
src/libcore/ops/arith.rs:pub trait Div<RHS=Self> {
src/libcore/ops/arith.rs:pub trait Rem<RHS=Self> {
src/libcore/ops/arith.rs:pub trait AddAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait SubAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait MulAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait DivAssign<Rhs=Self> {
src/libcore/ops/arith.rs:pub trait RemAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitAnd<RHS=Self> {
src/libcore/ops/bit.rs:pub trait BitOr<RHS=Self> {
src/libcore/ops/bit.rs:pub trait BitXor<RHS=Self> {
src/libcore/ops/bit.rs:pub trait Shl<RHS=Self> {
src/libcore/ops/bit.rs:pub trait Shr<RHS=Self> {
src/libcore/ops/bit.rs:pub trait BitAndAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitOrAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait BitXorAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait ShlAssign<Rhs=Self> {
src/libcore/ops/bit.rs:pub trait ShrAssign<Rhs=Self> {
src/liblibc/src/dox.rs:    pub trait Div<RHS=Self> {
src/liblibc/src/dox.rs:    pub trait Shl<RHS=Self> {
src/liblibc/src/dox.rs:    pub trait Mul<RHS=Self> {
src/liblibc/src/dox.rs:    pub trait Sub<RHS=Self> {
src/liblibc/src/dox.rs:    pub trait Bitor<RHS=Self> {
src/liblibc/src/dox.rs:    pub trait Add<RHS = Self> {
src/test/compile-fail/issue-28576.rs:pub trait Foo<RHS=Self> {
src/test/run-pass/trait-inheritance-subst.rs:pub trait Add<RHS,Result> {
src/test/rustdoc/auxiliary/issue-20727.rs:pub trait Add<RHS = Self> {
src/test/rustdoc/issue-20727-2.rs:pub trait Add<RHS = Self> {

The only case we haven't handled that I can see is the one in src/test/run-pass/trait-inheritance-subst.rs, which we probably don't care about.

[Mark-Simulacrum]

Crater has started. ETA is ~5 days.

[Mark-Simulacrum]

Crater results are at: http://cargobomb-reports.s3.amazonaws.com/pr-49630/index.html. 'Blacklisted' crates (spurious failures etc) can be found here. If you see any spurious failures not on the list, please make a PR against that file.

(interested observers: Crater is a tool for testing the impact of changes on the crates.io ecosystem. You can find out more at the repo if you're curious)

[npmccallum]

I'm new at this, but the failure don't appear to me to be related to this patch set.

[alexcrichton]

Yep those do indeed look spurious, so I think this is good to go!

@bors: r+

[bors]

📌 Commit 587098a has been approved by alexcrichton

[bors]

⌛ Testing commit 587098a with merge 883bf4b...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing 883bf4b to master...