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mruby-compiler: bail out of array-literal pattern match opt on splat

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The optimization that skips `deconstruct` and the size check when the
case/in value is an array literal trusted node count, ignoring splat.
An element like `*a` expands at runtime, so [*a] was treated as length
1 and matched only patterns of that length.

Fixes #6854.

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Yukihiro "Matz" Matsumoto
2026-05-22 18:39:38 +09:00
parent 3aea2f7e67
commit cddaec7264
2 changed files with 37 additions and 18 deletions
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mrbgems/mruby-compiler/core/codegen.c
+22 -18
View File
@@ -4285,6 +4285,22 @@ codegen_case(codegen_scope *s, node *varnode, int val)
*/
static void codegen_pattern(codegen_scope *s, node *pattern, int target, uint32_t *fail_pos, int known_array_len);
/* Return the static element count of an array literal AST node, or -1 if any
* element is a splat (whose runtime length is unknown).
*/
static int
array_literal_known_len(node *value)
{
if (node_type(value) != NODE_ARRAY) return -1;
struct mrb_ast_array_node *arr = array_node(value);
int len = 0;
for (node *elem = arr->elements; elem; elem = elem->cdr) {
if (is_splat_node(elem->car)) return -1;
len++;
}
return len;
}
/* Pattern matching case/in expression */
static void
codegen_case_match(codegen_scope *s, node *varnode, int val)
@@ -4298,13 +4314,7 @@ codegen_case_match(codegen_scope *s, node *varnode, int val)
uint32_t tmp;
/* Check if value is an array literal - allows optimizations in pattern matching */
int known_array_len = -1;
if (node_type(value) == NODE_ARRAY) {
struct mrb_ast_array_node *arr = array_node(value);
node *elem;
known_array_len = 0;
for (elem = arr->elements; elem; elem = elem->cdr) known_array_len++;
}
int known_array_len = array_literal_known_len(value);
/* Generate code for the case value */
codegen(s, value, VAL);
@@ -6552,16 +6562,15 @@ codegen(codegen_scope *s, node *tree, int val)
/* Optimize: array literal => array pattern with matching sizes */
if (node_type(mp->value) == NODE_ARRAY &&
node_type(mp->pattern) == NODE_PAT_ARRAY) {
struct mrb_ast_array_node *arr = array_node(mp->value);
struct mrb_ast_pat_array_node *pat = pat_array_node(mp->pattern);
/* Only optimize for exact match (no rest, no post) */
if (pat->rest == 0 && pat->post == NULL) {
/* Count array elements and pattern pre elements */
int arr_len = 0, pat_len = 0;
/* Count array elements (bail if splat present) and pattern pre elements */
int arr_len = array_literal_known_len(mp->value);
int pat_len = 0;
node *e;
for (e = arr->elements; e; e = e->cdr) arr_len++;
for (e = pat->pre; e; e = e->cdr) pat_len++;
if (arr_len == pat_len) {
if (arr_len >= 0 && arr_len == pat_len) {
/* Sizes match - skip deconstruct and size check */
int arr_reg = cursp();
int i = 0;
@@ -6600,12 +6609,7 @@ codegen(codegen_scope *s, node *tree, int val)
head = cursp();
/* Check if value is array literal for optimization */
if (node_type(mp->value) == NODE_ARRAY) {
struct mrb_ast_array_node *arr = array_node(mp->value);
node *elem;
known_array_len = 0;
for (elem = arr->elements; elem; elem = elem->cdr) known_array_len++;
}
known_array_len = array_literal_known_len(mp->value);
/* Evaluate the value */
codegen(s, mp->value, VAL);
test/t/syntax.rb
+15
View File
@@ -1043,6 +1043,21 @@ assert('pattern matching - array patterns') do
x
end
assert_equal 3, result
# array literal with splat as case value (#6854):
# the array-literal-length optimization must bail out for splat,
# since the runtime length is unknown statically.
a = [1, 2]
result = case [*a]
in [1, 2] then :match
else :nomatch
end
assert_equal :match, result
# same bug in one-line `in` pattern
assert_true ([*a] in [1, 2])
assert_false ([*a] in [1, 2, 3])
assert_true ([1, *a, 4] in [1, 1, 2, 4])
end
assert('pattern matching - find patterns') do