[ruby/prism] Add a test for multiple &nil blocks/mixing them

ruby/prism@e5fb0e192b

Author: Earlopain

lib/prism/node_ext.rb

@@ -286,7 +286,9 @@ def signature
         case param
         when MultiTargetNode
           names << [:req]
-        when NoKeywordsParameterNode, KeywordRestParameterNode, ForwardingParameterNode
+        when NoKeywordsParameterNode, KeywordRestParameterNode,
+            NoBlockParameterNode, BlockParameterNode,
+            ForwardingParameterNode
           # Invalid syntax, e.g. "def f(**nil, ...)" moves the NoKeywordsParameterNode to posts
           raise "Invalid syntax"
         else

prism/config.yml

@@ -4065,6 +4065,9 @@ nodes:
           - on error: NoKeywordsParameterNode
           # On parsing error of `f(..., ...)`, the first forwarding parameter is moved here:
           - on error: ForwardingParameterNode
+          # On parsing error of `f(&nil, &foo)`/`f(&foo, &nil)`, the first forwarding parameter is moved here:
+          - on error: BlockParameterNode
+          - on error: NoBlockParameterNode
       - name: keywords
         type: node[]
         kind:

test/prism/errors/4.1/multiple_blocks.txt

@@ -0,0 +1,12 @@
+def foo(&nil, &nil); end
+              ^ unexpected parameter order
+              ^~~~ multiple block parameters; only one block is allowed
+
+def foo(&foo, &nil); end
+              ^ unexpected parameter order
+              ^~~~ multiple block parameters; only one block is allowed
+
+def foo(&nil, &foo); end
+              ^ unexpected parameter order
+              ^~~~ multiple block parameters; only one block is allowed
+