[ruby/yarp] Fix endless method definitions binding power to accept args (#8051)

test/yarp/fixtures/endless_methods.txt

@@ -0,0 +1,5 @@
+def foo = 1
+
+def bar = A ""
+
+def method = 1 + 2 + 3

test/yarp/snapshots/endless_methods.txt

@@ -0,0 +1,80 @@
+ProgramNode(0...51)(
+  [],
+  StatementsNode(0...51)(
+    [DefNode(0...11)(
+       (4...7),
+       nil,
+       nil,
+       StatementsNode(10...11)([IntegerNode(10...11)()]),
+       [],
+       (0...3),
+       nil,
+       nil,
+       nil,
+       (8...9),
+       nil
+     ),
+     DefNode(13...27)(
+       (17...20),
+       nil,
+       nil,
+       StatementsNode(23...27)(
+         [CallNode(23...27)(
+            nil,
+            nil,
+            (23...24),
+            nil,
+            ArgumentsNode(25...27)(
+              [StringNode(25...27)((25...26), (26...26), (26...27), "")]
+            ),
+            nil,
+            nil,
+            0,
+            "A"
+          )]
+       ),
+       [],
+       (13...16),
+       nil,
+       nil,
+       nil,
+       (21...22),
+       nil
+     ),
+     DefNode(29...51)(
+       (33...39),
+       nil,
+       nil,
+       StatementsNode(42...51)(
+         [CallNode(42...51)(
+            CallNode(42...47)(
+              IntegerNode(42...43)(),
+              nil,
+              (44...45),
+              nil,
+              ArgumentsNode(46...47)([IntegerNode(46...47)()]),
+              nil,
+              nil,
+              0,
+              "+"
+            ),
+            nil,
+            (48...49),
+            nil,
+            ArgumentsNode(50...51)([IntegerNode(50...51)()]),
+            nil,
+            nil,
+            0,
+            "+"
+          )]
+       ),
+       [],
+       (29...32),
+       nil,
+       nil,
+       nil,
+       (40...41),
+       nil
+     )]
+  )
+)

yarp/yarp.c

@@ -10941,7 +10941,7 @@ parse_expression_prefix(yp_parser_t *parser, yp_binding_power_t binding_power) {
                 context_push(parser, YP_CONTEXT_DEF);
                 statements = (yp_node_t *) yp_statements_node_create(parser);
 
-                yp_node_t *statement = parse_expression(parser, YP_BINDING_POWER_ASSIGNMENT + 1, "Expected to be able to parse body of endless method definition.");
+                yp_node_t *statement = parse_expression(parser, YP_BINDING_POWER_DEFINED + 1, "Expected to be able to parse body of endless method definition.");
 
                 if (accept(parser, YP_TOKEN_KEYWORD_RESCUE_MODIFIER)) {
                     yp_token_t rescue_keyword = parser->previous;