diff --git a/packages/babel-generator/src/index.js b/packages/babel-generator/src/index.js
index d8fbaf2a4952..5be44e2d0254 100644
--- a/packages/babel-generator/src/index.js
+++ b/packages/babel-generator/src/index.js
@@ -10,9 +10,7 @@ import type { Format } from "./printer";
  */
 
 class Generator extends Printer {
-  constructor(ast, opts, code) {
-    opts = opts || {};
-
+  constructor(ast, opts = {}, code) {
     const tokens = ast.tokens || [];
     const format = normalizeOptions(code, opts, tokens);
     const map = opts.sourceMaps ? new SourceMap(opts, code) : null;
diff --git a/packages/babel-generator/src/node/parentheses.js b/packages/babel-generator/src/node/parentheses.js
index b469ef1703a9..0175a6312dd8 100644
--- a/packages/babel-generator/src/node/parentheses.js
+++ b/packages/babel-generator/src/node/parentheses.js
@@ -34,12 +34,8 @@ export function NullableTypeAnnotation(node: Object, parent: Object): boolean {
 export { NullableTypeAnnotation as FunctionTypeAnnotation };
 
 export function UpdateExpression(node: Object, parent: Object): boolean {
-  if (t.isMemberExpression(parent) && parent.object === node) {
-    // (foo++).test()
-    return true;
-  }
-
-  return false;
+  // (foo++).test()
+  return t.isMemberExpression(parent) && parent.object === node;
 }
 
 export function ObjectExpression(node: Object, parent: Object, printStack: Array<Object>): boolean {
@@ -51,15 +47,11 @@ export function DoExpression(node: Object, parent: Object, printStack: Array<Obj
 }
 
 export function Binary(node: Object, parent: Object): boolean {
-  if ((t.isCallExpression(parent) || t.isNewExpression(parent)) && parent.callee === node) {
-    return true;
-  }
-
-  if (t.isUnaryLike(parent)) {
-    return true;
-  }
-
-  if (t.isMemberExpression(parent) && parent.object === node) {
+  if (
+    ((t.isCallExpression(parent) || t.isNewExpression(parent)) && parent.callee === node) ||
+    t.isUnaryLike(parent) ||
+    (t.isMemberExpression(parent) && parent.object === node)
+  ) {
     return true;
   }
 
@@ -70,12 +62,11 @@ export function Binary(node: Object, parent: Object): boolean {
     const nodeOp = node.operator;
     const nodePos = PRECEDENCE[nodeOp];
 
-    if (parentPos > nodePos) {
-      return true;
-    }
-
-    // Logical expressions with the same precedence don't need parens.
-    if (parentPos === nodePos && parent.right === node && !t.isLogicalExpression(parent)) {
+    if (
+      // Logical expressions with the same precedence don't need parens.
+      (parentPos === nodePos && parent.right === node && !t.isLogicalExpression(parent)) ||
+      parentPos > nodePos
+    ) {
       return true;
     }
   }
@@ -84,55 +75,27 @@ export function Binary(node: Object, parent: Object): boolean {
 }
 
 export function BinaryExpression(node: Object, parent: Object): boolean {
-  if (node.operator === "in") {
-    // let i = (1 in []);
-    if (t.isVariableDeclarator(parent)) {
-      return true;
-    }
-
-    // for ((1 in []);;);
-    if (t.isFor(parent)) {
-      return true;
-    }
-  }
-
-  return false;
+  // let i = (1 in []);
+  // for ((1 in []);;);
+  return node.operator === "in" && (t.isVariableDeclarator(parent) || t.isFor(parent));
 }
 
 export function SequenceExpression(node: Object, parent: Object): boolean {
-  if (t.isForStatement(parent)) {
+
+  if (
     // Although parentheses wouldn"t hurt around sequence
     // expressions in the head of for loops, traditional style
     // dictates that e.g. i++, j++ should not be wrapped with
     // parentheses.
-    return false;
-  }
-
-  if (t.isExpressionStatement(parent) && parent.expression === node) {
-    return false;
-  }
-
-  if (t.isReturnStatement(parent)) {
-    return false;
-  }
-
-  if (t.isThrowStatement(parent)) {
-    return false;
-  }
-
-  if (t.isSwitchStatement(parent) && parent.discriminant === node) {
-    return false;
-  }
-
-  if (t.isWhileStatement(parent) && parent.test === node) {
-    return false;
-  }
-
-  if (t.isIfStatement(parent) && parent.test === node) {
-    return false;
-  }
-
-  if (t.isForInStatement(parent) && parent.right === node) {
+    t.isForStatement(parent) ||
+    t.isThrowStatement(parent) ||
+    t.isReturnStatement(parent) ||
+    (t.isIfStatement(parent) && parent.test === node) ||
+    (t.isWhileStatement(parent) && parent.test === node) ||
+    (t.isForInStatement(parent) && parent.right === node) ||
+    (t.isSwitchStatement(parent) && parent.discriminant === node) ||
+    (t.isExpressionStatement(parent) && parent.expression === node)
+  ) {
     return false;
   }
 
@@ -158,15 +121,9 @@ export function ClassExpression(node: Object, parent: Object, printStack: Array<
 }
 
 export function UnaryLike(node: Object, parent: Object): boolean {
-  if (t.isMemberExpression(parent, { object: node })) {
-    return true;
-  }
-
-  if (t.isCallExpression(parent, { callee: node }) || t.isNewExpression(parent, { callee: node })) {
-    return true;
-  }
-
-  return false;
+  return t.isMemberExpression(parent, { object: node }) ||
+         t.isCallExpression(parent, { callee: node }) ||
+         t.isNewExpression(parent, { callee: node });
 }
 
 export function FunctionExpression(node: Object, parent: Object, printStack: Array<Object>): boolean {
@@ -189,19 +146,12 @@ export function ArrowFunctionExpression(node: Object, parent: Object): boolean {
 }
 
 export function ConditionalExpression(node: Object, parent: Object): boolean {
-  if (t.isUnaryLike(parent)) {
-    return true;
-  }
-
-  if (t.isBinary(parent)) {
-    return true;
-  }
-
-  if (t.isConditionalExpression(parent, { test: node })) {
-    return true;
-  }
-
-  if (t.isAwaitExpression(parent)) {
+  if (
+    t.isUnaryLike(parent) ||
+    t.isBinary(parent) ||
+    t.isConditionalExpression(parent, { test: node }) ||
+    t.isAwaitExpression(parent)
+  ) {
     return true;
   }
 
@@ -227,28 +177,23 @@ function isFirstInStatement(printStack: Array<Object>, {
   i--;
   let parent = printStack[i];
   while (i > 0) {
-    if (t.isExpressionStatement(parent, { expression: node })) {
-      return true;
-    }
-
-    if (t.isTaggedTemplateExpression(parent)) {
-      return true;
-    }
-
-    if (considerDefaultExports && t.isExportDefaultDeclaration(parent, { declaration: node })) {
-      return true;
-    }
-
-    if (considerArrow && t.isArrowFunctionExpression(parent, { body: node })) {
+    if (
+      t.isExpressionStatement(parent, { expression: node }) ||
+      t.isTaggedTemplateExpression(parent) ||
+      considerDefaultExports && t.isExportDefaultDeclaration(parent, { declaration: node }) ||
+      considerArrow && t.isArrowFunctionExpression(parent, { body: node })
+    ) {
       return true;
     }
 
-    if ((t.isCallExpression(parent, { callee: node })) ||
-        (t.isSequenceExpression(parent) && parent.expressions[0] === node) ||
-        (t.isMemberExpression(parent, { object: node })) ||
-        (t.isConditional(parent, { test: node })) ||
-        (t.isBinary(parent, { left: node })) ||
-        (t.isAssignmentExpression(parent, { left: node }))) {
+    if (
+      t.isCallExpression(parent, { callee: node }) ||
+      (t.isSequenceExpression(parent) && parent.expressions[0] === node) ||
+      t.isMemberExpression(parent, { object: node }) ||
+      t.isConditional(parent, { test: node }) ||
+      t.isBinary(parent, { left: node }) ||
+      t.isAssignmentExpression(parent, { left: node })
+    ) {
       node = parent;
       i--;
       parent = printStack[i];
diff --git a/packages/babel-generator/src/printer.js b/packages/babel-generator/src/printer.js
index 7a7331e06c96..1941b94acee3 100644
--- a/packages/babel-generator/src/printer.js
+++ b/packages/babel-generator/src/printer.js
@@ -332,9 +332,11 @@ export default class Printer {
     this._maybeAddAuxComment(this._insideAux && !oldInAux);
 
     let needsParens = n.needsParens(node, parent, this._printStack);
-    if (this.format.retainFunctionParens &&
-        node.type === "FunctionExpression" &&
-        node.extra && node.extra.parenthesized) {
+    if (
+      this.format.retainFunctionParens &&
+      node.type === "FunctionExpression" &&
+      node.extra && node.extra.parenthesized
+    ) {
       needsParens = true;
     }
     if (needsParens) this.token("(");