clarify comment
Co-authored-by: scottmcm <scottmcm@users.noreply.github.com>
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs
index 009f945..6992856 100644
--- a/compiler/rustc_const_eval/src/interpret/operator.rs
+++ b/compiler/rustc_const_eval/src/interpret/operator.rs
@@ -324,7 +324,9 @@
}
}
- /// Returns the result of the specified operation, and whether it overflowed.
+ /// Returns the result of the specified operation.
+ ///
+ /// Whether this produces a scalar or a pair depends on the specific `bin_op`.
pub fn binary_op(
&self,
bin_op: mir::BinOp,
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 56aba3c0..c191de4 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -297,6 +297,8 @@
impl BinOp {
pub fn to_hir_binop(self) -> hir::BinOpKind {
match self {
+ // HIR `+`/`-`/`*` can map to either of these MIR BinOp, depending
+ // on whether overflow checks are enabled or not.
BinOp::Add | BinOp::AddWithOverflow => hir::BinOpKind::Add,
BinOp::Sub | BinOp::SubWithOverflow => hir::BinOpKind::Sub,
BinOp::Mul | BinOp::MulWithOverflow => hir::BinOpKind::Mul,
@@ -313,6 +315,7 @@
BinOp::Gt => hir::BinOpKind::Gt,
BinOp::Le => hir::BinOpKind::Le,
BinOp::Ge => hir::BinOpKind::Ge,
+ // We don't have HIR syntax for these.
BinOp::Cmp
| BinOp::AddUnchecked
| BinOp::SubUnchecked
