deoptimized a = delete b.c (gkz/LiveScript#273)

Author: satyr

lib/ast.js

@@ -282,7 +282,7 @@ exports.Block = Block = (function(superclass){
       break;
     default:
       this.lines.push(it);
-      if (that = it.back, delete it.back, that) {
+      if (that = (ref$ = it.back, delete it.back, ref$)) {
         this.back = that;
       }
     }
@@ -377,7 +377,7 @@ exports.Block = Block = (function(superclass){
       scope: this.scope = Scope.root = new Scope
     }, options));
     delete o.filename;
-    o.indent = (bare = o.bare, delete o.bare, bare) ? '' : TAB;
+    o.indent = (bare = (ref$ = o.bare, delete o.bare, ref$)) ? '' : TAB;
     if (/^\s*(?:[/#]|javascript:)/.test((ref$ = this.lines[0]) != null ? ref$.code : void 8)) {
       prefix = this.lines.shift().code + '\n';
     }
@@ -659,7 +659,7 @@ exports.Chain = Chain = (function(superclass){
         this.head.sproto = true;
       }
     }
-    if (that = it.vivify, delete it.vivify, that) {
+    if (that = (ref$ = it.vivify, delete it.vivify, ref$)) {
       this.head = Assign(Chain(this.head, this.tails.splice(0, 9e9)), that(), '=', '||');
     }
     return this;
@@ -1471,14 +1471,7 @@ exports.Unary = Unary = (function(superclass){
   prototype.compilePluck = function(o){
     var ref$, get, del, code, ref;
     ref$ = Chain(this.it).cacheReference(o), get = ref$[0], del = ref$[1];
-    code = this.assigned
-      ? ''
-      : (ref = o.scope.temporary()) + " = ";
-    code += get.compile(o, LEVEL_LIST) + ", delete " + del.compile(o, LEVEL_LIST);
-    if (this.assigned) {
-      return code;
-    }
-    code += ", " + o.scope.free(ref);
+    code = (ref = o.scope.temporary()) + " = " + get.compile(o, LEVEL_LIST) + ", delete " + del.compile(o, LEVEL_LIST) + ", " + o.scope.free(ref);
     if (o.level < LEVEL_LIST) {
       return code;
     } else {
@@ -1764,9 +1757,9 @@ exports.Assign = Assign = (function(superclass){
     }
   };
   prototype.unfoldSoak = function(o){
-    var that, ref$, rite, temps;
+    var that, ref$, ref1$, rite, temps;
     if (this.left instanceof Existence) {
-      if (that = (ref$ = this.left = this.left.it).name, delete ref$.name, that) {
+      if (that = (ref1$ = (ref$ = this.left = this.left.it).name, delete ref$.name, ref1$)) {
         rite = this.right;
         rite = Assign(this.right = Var(that), rite);
       } else {
@@ -1780,7 +1773,7 @@ exports.Assign = Assign = (function(superclass){
     return this.access && this;
   };
   prototype.compileNode = function(o){
-    var left, ref$, i$, len$, op, right, minmax, lefs, reft, ref, x0$, code, name, lvar, del, that, res;
+    var left, ref$, i$, len$, op, right, minmax, lefs, reft, ref, x0$, code, name, lvar, that, res;
     left = this.left.expandSlice(o, true).unwrap();
     if (!this.right) {
       left.isAssignable() || left.carp('invalid unary assign');
@@ -1833,7 +1826,6 @@ exports.Assign = Assign = (function(superclass){
     (right = right.unparen()).ripName(left = left.unwrap());
     code = name = (left.front = true, left).compile(o, LEVEL_LIST);
     if (lvar = left instanceof Var) {
-      del = right.op === 'delete';
       if (op === '=') {
         o.scope.declare(name, left, this['const']);
       } else if (that = o.scope.checkReadOnly(name)) {
@@ -1843,14 +1835,9 @@ exports.Assign = Assign = (function(superclass){
     code += " " + (replace$.call(op, ':', '')) + " ";
     code = !o.level && right instanceof While && !right['else'] && (lvar || left instanceof Chain && left.isSimpleAccess())
       ? (res = o.scope.temporary('res')) + " = [];\n" + this.tab + right.makeReturn(res).compile(o) + "\n" + this.tab + code + o.scope.free(res)
-      : code + (right.assigned = true, right).compile(o, LEVEL_LIST);
-    if (that = o.level) {
-      if (del) {
-        code += ", " + name;
-      }
-      if (that > (del ? LEVEL_PAREN : LEVEL_LIST)) {
-        code = "(" + code + ")";
-      }
+      : code + right.compile(o, LEVEL_LIST);
+    if (o.level > LEVEL_LIST) {
+      code = "(" + code + ")";
     }
     return code;
   };
@@ -2212,7 +2199,7 @@ exports.Fun = Fun = (function(superclass){
     this.name || (this.name = it.varName());
   };
   prototype.compileNode = function(o){
-    var pscope, sscope, scope, that, loop, body, name, tab, code, ref$;
+    var pscope, sscope, scope, that, loop, ref$, body, name, tab, code;
     pscope = o.scope;
     sscope = pscope.shared || pscope;
     scope = o.scope = this.body.scope = new Scope(this.wrapper ? pscope : sscope, this.wrapper && sscope);
@@ -2223,7 +2210,7 @@ exports.Fun = Fun = (function(superclass){
     if (that = this.cname) {
       scope.assign('constructor', that);
     }
-    if (loop = o.loop, delete o.loop, loop) {
+    if (loop = (ref$ = o.loop, delete o.loop, ref$)) {
       o.indent = this.tab = '';
     }
     o.indent += TAB;

src/ast.co

@@ -887,11 +887,10 @@ class exports.Unary extends Node
   # `v = delete o.k`
   compilePluck: (o) ->
     [get, del] = Chain @it .cacheReference o
-    code = if @assigned then '' else "#{ ref = o.scope.temporary! } = "
-    code +=   "#{ get.compile o, LEVEL_LIST }
-      , delete #{ del.compile o, LEVEL_LIST }"
-    return code if @assigned
-    code += ", #{ o.scope.free ref }"
+    code = "#{ ref = o.scope.temporary!  } = \
+            #{ get.compile o, LEVEL_LIST }, delete \
+            #{ del.compile o, LEVEL_LIST }, \
+            #{ o.scope.free ref }"
     if o.level < LEVEL_LIST then code else "(#code)"
 
 #### Binary operators
@@ -1106,7 +1105,6 @@ class exports.Assign extends Node
     (right.=unparen!)ripName left.=unwrap!
     code = name = (left <<< {+front})compile o, LEVEL_LIST
     if lvar = left instanceof Var
-      del = right.op is \delete
       if op is \=
         o.scope.declare name, left, @const
       else if o.scope.checkReadOnly name
@@ -1119,10 +1117,8 @@ class exports.Assign extends Node
          #{@tab}#{ right.makeReturn(res)compile o }
          #{@tab}#code#{ o.scope.free res }"""
     else
-      code + (right <<< {+assigned})compile o, LEVEL_LIST
-    if o.level
-      code += ", #name" if del
-      code  = "(#code)" if that > (if del then LEVEL_PAREN else LEVEL_LIST)
+      code + right.compile o, LEVEL_LIST
+    code = "(#code)" if o.level > LEVEL_LIST
     code
 
   !function lefseek node, lefs

test/operator.co

@@ -357,6 +357,8 @@ compileThrows 'invalid decrement'           1 'q.=p--'
 
 
 ### `delete`
+# - Disallows variable deletion.
+# - Returns the deleted value rather than the useless configurability check.
 i = 0
 O = ->
   switch ++i
@@ -369,6 +371,12 @@ eq o[7], void
 compileThrows 'invalid delete' 1 'delete a'
 compileThrows 'invalid delete' 1 'delete a.=b'
 
+# [livescript#273](https://github.com/gkz/LiveScript/issues/273)
+a = b = ^{0} <<< [1]
+a = delete a.0
+eq 1 a
+eq 0 b.0
+
 
 ### [[Class]] sniffing
 eq \RegExp typeof! /^/