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node_modules/core-js/internals/is-constructor.js

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+'use strict';
+var uncurryThis = require('../internals/function-uncurry-this');
+var fails = require('../internals/fails');
+var isCallable = require('../internals/is-callable');
+var classof = require('../internals/classof');
+var getBuiltIn = require('../internals/get-built-in');
+var inspectSource = require('../internals/inspect-source');
+
+var noop = function () { /* empty */ };
+var empty = [];
+var construct = getBuiltIn('Reflect', 'construct');
+var constructorRegExp = /^\s*(?:class|function)\b/;
+var exec = uncurryThis(constructorRegExp.exec);
+var INCORRECT_TO_STRING = !constructorRegExp.exec(noop);
+
+var isConstructorModern = function isConstructor(argument) {
+  if (!isCallable(argument)) return false;
+  try {
+    construct(noop, empty, argument);
+    return true;
+  } catch (error) {
+    return false;
+  }
+};
+
+var isConstructorLegacy = function isConstructor(argument) {
+  if (!isCallable(argument)) return false;
+  switch (classof(argument)) {
+    case 'AsyncFunction':
+    case 'GeneratorFunction':
+    case 'AsyncGeneratorFunction': return false;
+  }
+  try {
+    // we can't check .prototype since constructors produced by .bind haven't it
+    // `Function#toString` throws on some built-it function in some legacy engines
+    // (for example, `DOMQuad` and similar in FF41-)
+    return INCORRECT_TO_STRING || !!exec(constructorRegExp, inspectSource(argument));
+  } catch (error) {
+    return true;
+  }
+};
+
+isConstructorLegacy.sham = true;
+
+// `IsConstructor` abstract operation
+// https://tc39.es/ecma262/#sec-isconstructor
+module.exports = !construct || fails(function () {
+  var called;
+  return isConstructorModern(isConstructorModern.call)
+    || !isConstructorModern(Object)
+    || !isConstructorModern(function () { called = true; })
+    || called;
+}) ? isConstructorLegacy : isConstructorModern;