Remove string concat node in prism

prism_compile.c

@@ -3686,15 +3686,6 @@ pm_compile_node(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *const ret,
         }
         return;
       }
-      case PM_STRING_CONCAT_NODE: {
-        pm_string_concat_node_t *str_concat_node = (pm_string_concat_node_t *)node;
-        PM_COMPILE(str_concat_node->left);
-        PM_COMPILE(str_concat_node->right);
-        if (!popped) {
-            ADD_INSN1(ret, &dummy_line_node, concatstrings, INT2FIX(2));
-        }
-        return;
-      }
       case PM_STRING_NODE: {
         if (!popped) {
             pm_string_node_t *string_node = (pm_string_node_t *) node;

test/ruby/test_compile_prism.rb

@@ -417,6 +417,7 @@ module Prism
     def test_InterpolatedStringNode
       assert_prism_eval('$pit = 1; "1 #$pit 1"')
       assert_prism_eval('"1 #{1 + 2} 1"')
+      assert_prism_eval('"Prism" "::" "TestCompilePrism"')
     end
 
     def test_InterpolatedSymbolNode
@@ -461,10 +462,6 @@ module Prism
       assert_prism_eval('2.times.map { /#{1}/o }')
     end
 
-    def test_StringConcatNode
-      assert_prism_eval('"Prism" "::" "TestCompilePrism"')
-    end
-
     def test_StringNode
       assert_prism_eval('"pit"')
     end