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Allow .. ranges to use "a..a-1" in order to express zero length.

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This commit is contained in:
Christoffer Lerno
2025-10-10 00:34:30 +02:00
parent f3b7df2ab0
commit df67b7dddd
5 changed files with 152 additions and 8 deletions
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7
src/compiler/sema_expr.c
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@@ -4258,6 +4258,7 @@ INLINE bool sema_expr_analyse_range_internal(SemaContext *context, Range *range,
if (!sema_analyse_expr_rvalue(context, start)) return false;
if (end && !sema_analyse_expr_rvalue(context, end)) return false;
ArrayIndex lowest = range->is_len ? 0 : -1;
if (!cast_to_index_len(context, start, false)) return false;
if (end && !cast_to_index_len(context, end, false)) return false;
Type *end_type = end ? type_no_optional(end->type) : NULL;
@@ -4307,14 +4308,14 @@ INLINE bool sema_expr_analyse_range_internal(SemaContext *context, Range *range,
// Something like 1 .. ^4 with an unknown length.
if (len < 0) return true;
// Otherwise we fold the "from end"
if (end_index > len)
if (end_index + lowest > len)
{
RETURN_SEMA_ERROR(end, "An index may only be negative for pointers (it was: %lld).", len - end_index);
}
end_index = len - end_index;
range->end_from_end = false;
}
if (end_index < 0 && env != RANGE_PTR)
if (end_index < lowest && env != RANGE_PTR)
{
RETURN_SEMA_ERROR(end, "An index may only be negative for pointers (it was: %lld).", end_index);
}
@@ -4363,7 +4364,7 @@ INLINE bool sema_expr_analyse_range_internal(SemaContext *context, Range *range,
if (range->range_type == RANGE_CONST_END)
{
ArrayIndex end_index = range->const_end;
if (end_index < start_index) RETURN_SEMA_ERROR(start, "The start index (%lld) should not be greater than the end index (%lld).",
if (end_index - lowest < start_index) RETURN_SEMA_ERROR(start, "The start index (%lld) should not be greater than the end index (%lld).",
start_index, end_index);
range->const_end = end_index + 1 - start_index;
range->range_type = RANGE_CONST_LEN;