remove declarations transformer and instead do it whenever we push a generated declaration, better for perf and removes shitty bugs - fixes #1268

src/babel/transformation/file/index.js

@@ -41,10 +41,11 @@ export default class File {
     this.dynamicImportIds   = {};
     this.dynamicImports     = [];
 
-    this.usedHelpers = {};
-    this.dynamicData = {};
-    this.data        = {};
-    this.uids        = {};
+    this.declarations = {};
+    this.usedHelpers  = {};
+    this.dynamicData  = {};
+    this.data         = {};
+    this.uids         = {};
 
     this.log  = new Logger(this, opts.filename || "unknown");
     this.opts = this.normalizeOptions(opts);
@@ -395,8 +396,8 @@ export default class File {
 
     var program = this.ast.program;
 
-    var declar = program._declarations && program._declarations[name];
-    if (declar) return declar.id;
+    var declar = this.declarations[name];
+    if (declar) return declar;
 
     this.usedHelpers[name] = true;
 
@@ -413,11 +414,11 @@ export default class File {
 
     var ref = util.template("helper-" + name);
     ref._compact = true;
-    var uid = this.scope.generateUidIdentifier(name);
+    var uid = this.declarations[name] = this.scope.generateUidIdentifier(name);
     this.scope.push({
-      key: name,
       id: uid,
-      init: ref
+      init: ref,
+      unique: true
     });
     return uid;
   }

src/babel/transformation/transformers/es6/spec.symbols.js

@@ -21,3 +21,7 @@ export function UnaryExpression(node, parent, scope, file) {
     }
   }
 }
+
+export function VariableDeclaration(node) {
+  if (node._generated) this.skip();
+}

src/babel/transformation/transformers/index.js

@@ -94,8 +94,6 @@ export default {
 
   "spec.protoToAssign":                    require("./spec/proto-to-assign"),
 
-  _declarations:                           require("./internal/declarations"),
-
   _shadowFunctions:                        require("./internal/shadow-functions"),
 
   "es7.doExpressions":                     require("./es7/do-expressions"),

src/babel/transformation/transformers/internal/declarations.js

@@ -1,37 +0,0 @@
-import * as strict from "../../helpers/strict";
-import * as t from "../../../types";
-
-export var metadata = {
-  secondPass: true
-};
-
-export function BlockStatement(node, parent, scope, file) {
-  if (!node._declarations) return;
-
-  strict.wrap(node, function () {
-    var kinds = {};
-    var kind;
-
-    for (var i in node._declarations) {
-      var declar = node._declarations[i];
-
-      kind = declar.kind || "var";
-      var declarNode = t.variableDeclarator(declar.id, declar.init);
-
-      if (declar.init) {
-        node.body.unshift(file.attachAuxiliaryComment(t.variableDeclaration(kind, [declarNode])));
-      } else {
-        kinds[kind] ||= [];
-        kinds[kind].push(declarNode);
-      }
-    }
-
-    for (kind in kinds) {
-      node.body.unshift(file.attachAuxiliaryComment(t.variableDeclaration(kind, kinds[kind])));
-    }
-
-    node._declarations = null;
-  });
-}
-
-export { BlockStatement as Program };

src/babel/traversal/index.js

@@ -76,7 +76,7 @@ traverse.node = function (node, opts, scope, state, parentPath) {
 
 const CLEAR_KEYS = [
   "trailingComments", "leadingComments", "extendedRange",
-  "_declarations", "_scopeInfo" ,"_paths",
+  "_scopeInfo" ,"_paths",
   "tokens", "range", "start", "end", "loc", "raw"
 ];
 

src/babel/traversal/scope.js

@@ -516,23 +516,35 @@ export default class Scope {
    */
 
   push(opts: Object) {
-    var block = this.block;
+    var path = this.path;
 
-    if (t.isLoop(block) || t.isCatchClause(block) || t.isFunction(block)) {
-      t.ensureBlock(block);
-      block = block.body;
+    if (path.isLoop() || path.isCatchClause() || path.isFunction()) {
+      t.ensureBlock(path.node);
+      path = path.get("body");
     }
 
-    if (!t.isBlockStatement(block) && !t.isProgram(block)) {
-      block = this.getBlockParent().block;
+    if (!path.isBlockStatement() && !path.isProgram()) {
+      path = this.getBlockParent().path;
     }
 
-    block._declarations ||= {};
-    block._declarations[opts.key || opts.id.name] = {
-      kind: opts.kind || "var",
-      id: opts.id,
-      init: opts.init
-    };
+    var unique = opts.unique;
+    var kind   = opts.kind || "var";
+
+    var dataKey = `declaration:${kind}`;
+    var declar  = !unique && path.getData(dataKey);
+
+    if (!declar) {
+      declar = t.variableDeclaration(opts.kind || "var", []);
+      declar._generated = true;
+      declar._blockHoist = 2;
+
+      this.file.attachAuxiliaryComment(declar);
+
+      path.get("body")[0]._containerInsertBefore([declar]);
+      if (!unique) path.setData(dataKey, declar);
+    }
+
+    declar.declarations.push(t.variableDeclarator(opts.id, opts.init));
   }
 
   /**

src/babel/types/index.js

@@ -282,12 +282,11 @@ export function inheritsComments(child: Object, parent: Object): Object {
 export function inherits(child: Object, parent: Object): Object {
   if (!child || !parent) return child;
 
-  child._declarations = parent._declarations;
-  child._scopeInfo    = parent._scopeInfo;
-  child.range         = parent.range;
-  child.start         = parent.start;
-  child.loc           = parent.loc;
-  child.end           = parent.end;
+  child._scopeInfo = parent._scopeInfo;
+  child.range      = parent.range;
+  child.start      = parent.start;
+  child.loc        = parent.loc;
+  child.end        = parent.end;
 
   child.typeAnnotation = parent.typeAnnotation;
   child.returnType     = parent.returnType;