Fix crash when using arithmetic expressions in pattern matching

When arithmetic expressions like `-1**2` are used in pattern matching
contexts, Ruby crashes with "Unexpected node type in pattern matching
expression: PM_CALL_NODE". This happens because the Prism parser creates
PM_CALL_NODE for arithmetic operations, but Ruby's pattern matching
compiler doesn't handle call nodes.

This fix adds validation to reject PM_CALL_NODE in pattern contexts with a
proper syntax error.

Author: st0012

src/prism.c

@@ -17393,6 +17393,14 @@ parse_pattern_primitive(pm_parser_t *parser, pm_constant_id_list_t *captures, pm
             // If we found a label, we need to immediately return to the caller.
             if (pm_symbol_node_label_p(node)) return node;
 
+            // Call nodes (arithmetic operations) are not allowed in patterns
+            if (PM_NODE_TYPE(node) == PM_CALL_NODE) {
+                pm_parser_err_node(parser, node, diag_id);
+                pm_missing_node_t *missing_node = pm_missing_node_create(parser, node->location.start, node->location.end);
+                xfree(node);
+                return (pm_node_t *) missing_node;
+            }
+
             // Now that we have a primitive, we need to check if it's part of a range.
             if (accept2(parser, PM_TOKEN_DOT_DOT, PM_TOKEN_DOT_DOT_DOT)) {
                 pm_token_t operator = parser->previous;

test/prism/errors/pattern_arithmetic_expressions.txt

@@ -0,0 +1,3 @@
+case 1; in -1**2; end
+           ^~~~~ expected a pattern expression after the `in` keyword
+