message: Simplify import pattern
diff: @@ -3,12 +3,7 @@ import { DelegateToEditor } from "./i-delegate-to-editor";
  import { ShowErrorMessage, ErrorReason } from "./i-show-error-message";
  import { renameSymbol } from "./rename-symbol";
  import { Selection } from "./selection";
  -import {
  - traverseAST,
  - isStringLiteral,
  - isNumericLiteral,
  - isBooleanLiteral
  -} from "./ast";
  +import * as ast from "./ast";
  export { extractVariable };
  @@ -23,12 +18,13 @@ async function extractVariable(
  let indentationLevel = 0;
  let extractedSelection = selection;
  - traverseAST(code, {
  + ast.traverseAST(code, {
  enter(path) {
  if (
  - !isStringLiteral(path.node) &&
  - !isNumericLiteral(path.node) &&
  - !isBooleanLiteral(path.node)
  + !ast.isStringLiteral(path.node) &&
  + !ast.isNumericLiteral(path.node) &&
  + !ast.isBooleanLiteral(path.node) &&
  + !ast.isNullLiteral(path.node)
  )
  return;
  if (!path.node.loc) return;
  @@ -36,7 +32,7 @@ async function extractVariable(
  const selectionInAST = Selection.fromAST(path.node.loc);
  if (selection.isInside(selectionInAST)) {
  // If extracted code is a string, we want the raw value with the quotes.
  - extractedCode = isStringLiteral(path.node)
  + extractedCode = ast.isStringLiteral(path.node)
  ? path.node.extra.raw
  : path.node.value;
  extractedSelection = selectionInAST;
  