Tracking Issue for inherent unchecked integer methods · Issue #85122 · rust-lang/rust (original) (raw)

This is a tracking issue for the unchecked_* methods on integers.

unchecked_math (stable as of #122520)

impl uN { pub const unsafe fn unchecked_add(self, rhs: uN) -> uN; pub const unsafe fn unchecked_sub(self, rhs: uN) -> uN; pub const unsafe fn unchecked_mul(self, rhs: uN) -> uN; } impl iN { pub const unsafe fn unchecked_add(self, rhs: iN) -> iN; pub const unsafe fn unchecked_sub(self, rhs: iN) -> iN; pub const unsafe fn unchecked_mul(self, rhs: iN) -> iN; }

Steps / History

• Rework the std::iter::Step trait #69659 added unchecked_{add,sub,mul}
• Make unchecked_{add,sub,mul} inherent methods unstably const #85096
• Clean up unchecked_math, separate out unchecked_shifts #115626
• Stabilize unchecked_{add,sub,mul} #122520
• Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods #121571

unchecked_neg

impl iN { pub const unsafe fn unchecked_neg(self) -> iN; }

Steps / History

• Clean up unchecked_math, separate out unchecked_shifts #115626 added unchecked_neg
• Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods #121571

unchecked_shifts

impl uN { pub const unsafe fn unchecked_shl(self, rhs: u32) -> uN; pub const unsafe fn unchecked_shr(self, rhs: u32) -> uN; } impl iN { pub const unsafe fn unchecked_shl(self, rhs: u32) -> iN; pub const unsafe fn unchecked_shr(self, rhs: u32) -> iN; }

Steps / History

• Add inherent unchecked_shl, unchecked_shr to integers #85703
• unchecked_{shl|shr} should use u32 as the RHS #103456
• Clean up unchecked_math, separate out unchecked_shifts #115626
• Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods #121571

unchecked_* (aggregate)

impl uN { pub const unsafe fn unchecked_add(self, rhs: uN) -> uN; pub const unsafe fn unchecked_sub(self, rhs: uN) -> uN; pub const unsafe fn unchecked_mul(self, rhs: uN) -> uN; pub const unsafe fn unchecked_shl(self, rhs: u32) -> uN; pub const unsafe fn unchecked_shr(self, rhs: u32) -> uN; } impl iN { pub const unsafe fn unchecked_add(self, rhs: iN) -> iN; pub const unsafe fn unchecked_sub(self, rhs: iN) -> iN; pub const unsafe fn unchecked_mul(self, rhs: iN) -> iN; pub const unsafe fn unchecked_shl(self, rhs: u32) -> iN; pub const unsafe fn unchecked_shr(self, rhs: u32) -> iN; pub const unsafe fn unchecked_neg(self) -> iN; }

Steps / History

• Rework the std::iter::Step trait #69659 added unchecked_{add,sub,mul}
• Make unchecked_{add,sub,mul} inherent methods unstably const #85096
• Add inherent unchecked_shl, unchecked_shr to integers #85703
• unchecked_{shl|shr} should use u32 as the RHS #103456
• Clean up unchecked_math, separate out unchecked_shifts #115626 added unchecked_neg
• Stabilize unchecked_{add,sub,mul} #122520
• Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods #121571
• Final commenting period (FCP)
• Stabilization PR

Unresolved Questions

• Should the other unchecked intrinsics like exact_div also get inherent versions?
• From Add inherent unchecked_shl, unchecked_shr to integers #85703, consider if distinguishing the different kinds of ub could be useful (UB from overflow like MIN/-1 or MAX+1, LLVM's n[us]w; UB from input range like x/0 or x << -1; UB from lossy like 2/4 or 3 >> 1, LLVM's exact)

Resolved unresolved questions:

• Is unchecked_* the best naming for these? We stabilised unchecked_{add,sub,mul} already, so, yes.