add unless block

Author: leafo

moonscript/parse.lua

@@ -404,6 +404,9 @@ local build_grammar = wrap_env(function()
 			((Break * CheckIndent)^-1 * EmptyLine^0 * key"elseif" * IfCond * key"then"^-1 * Body / mark"elseif")^0 *
 			((Break * CheckIndent)^-1 * EmptyLine^0 * key"else" * Body / mark"else")^-1 / mark"if",
 
+		Unless = key"unless" * IfCond * key"then"^-1 * Body *
+			((Break * CheckIndent)^-1 * EmptyLine^0 * key"else" * Body / mark"else")^-1 / mark"unless",
+
 		While = key"while" * Exp * key"do"^-1 * Body / mark"while",
 
 		For = key"for" * (Name * sym"=" * Ct(Exp * sym"," * Exp * (sym"," * Exp)^-1)) *
@@ -435,7 +438,7 @@ local build_grammar = wrap_env(function()
 		-- Term = Ct(Value * (TermOp * Value)^0) / flatten_or_mark"exp",
 
 		SimpleValue =
-			If +
+			If + Unless +
 			Switch +
 			With +
 			ForEach + For + While +

moonscript/transform.lua

@@ -549,6 +549,19 @@ Statement = Transformer({
     end
     return node
   end,
+  unless = function(self, node)
+    return {
+      "if",
+      {
+        "not",
+        {
+          "parens",
+          node[2]
+        }
+      },
+      unpack(node, 3)
+    }
+  end,
   ["if"] = function(self, node, ret)
     if ntype(node[2]) == "assign" then
       local _, assign, body = unpack(node)
@@ -1284,6 +1297,11 @@ Value = Transformer({
       node
     })
   end,
+  unless = function(self, node)
+    return build.block_exp({
+      node
+    })
+  end,
   with = function(self, node)
     return build.block_exp({
       node

moonscript/transform.moon

@@ -244,8 +244,10 @@ Statement = Transformer {
     node[2] = apply_to_last node[2], ret if ret
     node
 
-  if: (node, ret) =>
+  unless: (node) =>
+    { "if", {"not", {"parens", node[2]}}, unpack node, 3 }
 
+  if: (node, ret) =>
     -- expand assign in cond
     if ntype(node[2]) == "assign"
       _, assign, body = unpack node
@@ -684,6 +686,7 @@ Value = Transformer {
     node
 
   if: (node) => build.block_exp { node }
+  unless: (node) =>build.block_exp { node }
   with: (node) => build.block_exp { node }
   switch: (node) =>
     build.block_exp { node }

moonscript/types.lua

@@ -10,6 +10,7 @@ manual_return = data.Set({
 })
 cascading = data.Set({
   "if",
+  "unless",
   "with",
   "switch"
 })

moonscript/types.moon

@@ -12,7 +12,7 @@ import insert from table
 manual_return = data.Set{"foreach", "for", "while", "return"}
 
 -- assigns and returns are bubbled into their bodies
-cascading = data.Set{ "if", "with", "switch" }
+cascading = data.Set{ "if", "unless", "with", "switch" }
 
 is_value = (stm) ->
   import compile, transform from moonscript

tests/inputs/cond.moon

@@ -89,3 +89,56 @@ elseif z = true
 else
   four
 
+---
+
+unless true
+  print "cool!"
+
+unless true and false
+  print "cool!"
+
+unless false then print "cool!"
+unless false then print "cool!" else print "no way!"
+
+unless nil
+  print "hello"
+else
+  print "world"
+
+--
+
+x = unless true
+  print "cool!"
+
+x = unless true and false
+  print "cool!"
+
+x = unless false then print "cool!"
+x = unless false then print "cool!" else print "no way!"
+
+x = unless nil
+  print "hello"
+else
+  print "world"
+
+print unless true
+  print "cool!"
+
+print unless true and false
+  print "cool!"
+
+print unless false then print "cool!"
+print unless false then print "cool!" else print "no way!"
+
+print unless nil
+  print "hello"
+else
+  print "world"
+
+--
+
+print "hello" unless value
+
+dddd = {1,2,3} unless value
+
+

tests/outputs/cond.lua

@@ -149,4 +149,82 @@ else
       end
     end
   end
+end
+if not (true) then
+  print("cool!")
+end
+if not (true and false) then
+  print("cool!")
+end
+if not (false) then
+  print("cool!")
+end
+if not (false) then
+  print("cool!")
+else
+  print("no way!")
+end
+if not (nil) then
+  print("hello")
+else
+  print("world")
+end
+local x
+if not (true) then
+  x = print("cool!")
+end
+if not (true and false) then
+  x = print("cool!")
+end
+if not (false) then
+  x = print("cool!")
+end
+if not (false) then
+  x = print("cool!")
+else
+  x = print("no way!")
+end
+if not (nil) then
+  x = print("hello")
+else
+  x = print("world")
+end
+print((function()
+  if not (true) then
+    return print("cool!")
+  end
+end)())
+print((function()
+  if not (true and false) then
+    return print("cool!")
+  end
+end)())
+print((function()
+  if not (false) then
+    return print("cool!")
+  end
+end)())
+print((function()
+  if not (false) then
+    return print("cool!")
+  else
+    return print("no way!")
+  end
+end)())
+print((function()
+  if not (nil) then
+    return print("hello")
+  else
+    return print("world")
+  end
+end)())
+if not (value) then
+  print("hello")
+end
+if not (value) then
+  local dddd = {
+    1,
+    2,
+    3
+  }
 end