Merge pull request #348 from ef4/map-child-nodes

Refactor child mapping & scope boundary detection

src/compiler.coffee

@@ -1,4 +1,4 @@
-{any, concat, concatMap, difference, divMod, foldl1, intersect, map, nub, owns, partition, span, union} = require './functional-helpers'
+{any, concat, concatMap, difference, divMod, foldl, foldl1, intersect, map, nub, owns, partition, span, union} = require './functional-helpers'
 {beingDeclared, usedAsExpression, envEnrichments} = require './helpers'
 CS = require './nodes'
 JS = require './js-nodes'
@@ -15,6 +15,29 @@ jsReserved = [
  'typeof', 'var', 'void', 'while', 'with', 'yield', 'arguments', 'eval'
 ]
 
+# mapper has type (node, nameInParent) -> A
+# reducer has type (B, A) -> B
+# identity has type B
+# opts contains optional overrides:
+# listReducer
+# listIdentity
+#
+# Runs the mapper over every child node, then folds them together with
+# the reducer & identity.
+#
+# listReducer and listIdentity are optional and let you use a different
+# reducing function for siblings in the same child listMember than you
+# use between disparate children.
+#
+mapChildNodes = (node, mapper, reducer, identity, opts={}) ->
+ opts.listReducer ?= reducer
+ opts.listIdentity ?= identity
+ foldl identity, (for childName in node.childNodes when node[childName]?
+ if childName in node.listMembers
+ foldl opts.listIdentity, (mapper(child, childName) for child in node[childName] when child?), opts.listReducer
+ else
+ mapper(node[childName], childName)
+ ), reducer
 
 genSym = do ->
  genSymCounter = 0
@@ -74,6 +97,9 @@ expr = (s) ->
  # TODO: comprehensive
  throw new Error "expr: Cannot use a #{s.type} as a value"
 
+isScopeBoundary = (node) ->
+ (node.instanceof JS.FunctionExpression, JS.FunctionDeclaration) and not node.generated
+
 makeReturn = (node) ->
  return new JS.ReturnStatement unless node?
  if node.instanceof JS.BlockStatement
@@ -99,15 +125,12 @@ makeReturn = (node) ->
 
 
 generateMutatingWalker = (fn) -> (node, args...) ->
- for childName in node.childNodes
- continue unless node[childName]?
- node[childName] =
- if childName in node.listMembers
- for n in node[childName]
- fn.apply n, args
- else
- fn.apply node[childName], args
- node
+ mapper = (child, nameInParent) -> [nameInParent, fn.apply(child, args)]
+ reducer = (parent, [name, newChild]) -> parent[name] = newChild; parent
+ mapChildNodes node, mapper, reducer, node, {
+ listReducer: ([_, accum],[name, newChild]) -> [name, accum.concat(newChild) ]
+ listIdentity: [null, []]
+ }
 
 declarationsNeeded = (node) ->
  return [] unless node?
@@ -117,45 +140,29 @@ declarationsNeeded = (node) ->
 
 declarationsNeededRecursive = (node) ->
  return [] unless node?
- # don't cross scope boundaries
- if (node.instanceof JS.FunctionExpression, JS.FunctionDeclaration) and not node.generated then []
- else union (declarationsNeeded node), concatMap node.childNodes, (childName) ->
- # TODO: this should make use of an fmap method
- return [] unless node[childName]?
- if childName in node.listMembers then concatMap node[childName], declarationsNeededRecursive
- else declarationsNeededRecursive node[childName]
+ if isScopeBoundary(node) then []
+ else union (declarationsNeeded node), mapChildNodes(node, declarationsNeededRecursive, ((a,b)->a.concat(b)), [])
 
 variableDeclarations = (node) ->
  return [] unless node?
- # don't cross scope boundaries
  if node.instanceof JS.FunctionDeclaration then [node.id]
- else if (node.instanceof JS.FunctionExpression) and not node.generated then []
+ else if isScopeBoundary(node) then []
  else if node.instanceof JS.VariableDeclarator then [node.id]
- else concatMap node.childNodes, (childName) ->
- # TODO: this should make use of an fmap method
- return [] unless node[childName]?
- if childName in node.listMembers then concatMap node[childName], variableDeclarations
- else variableDeclarations node[childName]
+ else mapChildNodes(node, variableDeclarations, ((a,b)->a.concat(b)), [])
 
 collectIdentifiers = (node) -> nub switch
  when !node? then []
  when node.instanceof JS.Identifier then [node.name]
  when (node.instanceof JS.MemberExpression) and not node.computed
  collectIdentifiers node.object
- else concatMap node.childNodes, (childName) ->
- return [] unless node[childName]?
- if childName in node.listMembers
- concatMap node[childName], collectIdentifiers
- else
- collectIdentifiers node[childName]
+ else mapChildNodes node, collectIdentifiers, ((a,b)->a.concat(b)), []
 
 # TODO: something like Optimiser.mayHaveSideEffects
 needsCaching = (node) ->
  return no unless node?
  (envEnrichments node, []).length > 0 or
  (node.instanceof CS.FunctionApplications, CS.DoOp, CS.NewOp, CS.ArrayInitialiser, CS.ObjectInitialiser, CS.RegExp, CS.HeregExp, CS.PreIncrementOp, CS.PostIncrementOp, CS.PreDecrementOp, CS.PostDecrementOp, CS.Range) or
- (any (difference node.childNodes, node.listMembers), (n) -> needsCaching node[n]) or
- any node.listMembers, (n) -> any node[n], needsCaching
+ mapChildNodes node, needsCaching, ((a,b) -> a or b), false
 
 forceBlock = (node) ->
  return new JS.BlockStatement [] unless node?
@@ -1094,7 +1101,7 @@ class exports.Compiler
  newNode = new JS.Identifier generateName this, state
  usedSymbols.push newNode.name
  newNode
- else if (@instanceof JS.FunctionExpression, JS.FunctionDeclaration) and not @generated
+ else if isScopeBoundary(this)
  params = concatMap @params, collectIdentifiers
  nsCounters_ = {}
  nsCounters_[k] = v for own k, v of nsCounters