`checksum += parsed[i].score` (a number local plus an `any` value) failed
with SC1043 "comparing non-number, non-string values" in TypeScript, while
the expanded `checksum = checksum + parsed[i].score` compiled: the
compound lowering only routed checked-dynamic operands through the
runtime operators in JavaScript files.
Locals, record fields and array elements now lower `op=` with an untyped
right operand (or an untyped local target) exactly like `x = x op rhs`:
dyn.add / dyn.arithmetic / dyn.bitwise, then the checked conversion into
the target's declared type. Numeric operators keep Node's ToNumber
semantics; a `+=` that produces a string for a `number` target throws the
same catchable TypeError as the expanded assignment and leaves the target
unchanged (pinned in tests/harness/dyncheck.test.ts).
Remaining SC1043 refusals for arithmetic, unary, update and compound
operators now name the operator and operand types instead of the
comparison wording.
The retired-engine-763 diagnostics fixture compiles now and matches Node,
so it moves to the corpus as 5343.
Malte Ubl
6cd96eec49