handle general case of block_exp single assign

Author: leafo

moonscript/transform.lua

@@ -351,28 +351,35 @@ Statement = Transformer({
     local num_names = #values
     if num_names == 1 and num_values == 1 then
       local first_value = values[1]
+      local first_name = names[1]
       local _exp_0 = ntype(first_value)
-      if "comprehension" == _exp_0 then
-        local first_name = names[1]
-        local a = Accumulator()
-        local action
-        action = function(exp)
-          return a:mutate_body({
-            exp
-          })
-        end
-        node = self.transform.statement(first_value, action, node)
-        local wrapped = a:wrap(node, "do")
-        insert(wrapped[2], build.assign_one(first_name, a.accum_name))
+      if "block_exp" == _exp_0 then
+        local block_body = first_value[2]
+        local idx = #block_body
+        block_body[idx] = build.assign_one(first_name, block_body[idx])
         return build.group({
           {
             "declare",
             {
               first_name
             }
           },
-          wrapped
+          {
+            "do",
+            block_body
+          }
         })
+      elseif "comprehension" == _exp_0 then
+        local a = Accumulator()
+        local action
+        action = function(exp)
+          return a:mutate_body({
+            exp
+          })
+        end
+        node = self.transform.statement(first_value, action, node)
+        local wrapped = a:wrap(node)
+        return build.assign_one(first_name, wrapped)
       end
     end
     local transformed

moonscript/transform.moon

@@ -174,23 +174,29 @@ Statement = Transformer {
     num_values = #values
     num_names = #values
 
+    -- special code simplifications for single assigns
     if num_names == 1 and num_values == 1
       first_value = values[1]
+      first_name = names[1]
+
       switch ntype first_value
-        when "comprehension"
-          first_name = names[1]
+        when "block_exp"
+          block_body = first_value[2]
+          idx = #block_body
+          block_body[idx] = build.assign_one first_name, block_body[idx]
+
+          return build.group {
+            {"declare", {first_name}}
+            {"do", block_body}
+          }
 
+        when "comprehension"
           a = Accumulator!
           action = (exp) -> a\mutate_body { exp }
           node = @transform.statement first_value, action, node
 
-          wrapped = a\wrap node, "do"
-          insert wrapped[2], build.assign_one first_name, a.accum_name
-
-          return build.group {
-            {"declare", {first_name}}
-            wrapped
-          }
+          wrapped = a\wrap node
+          return build.assign_one first_name, wrapped
 
     -- bubble cascading assigns
     transformed = if num_values == 1