The inferred type of `this` is wrong

[basarat]

On this file

declare var require:any;

var HTMLDOMPropertyConfig = require('react/lib/HTMLDOMPropertyConfig');

// Populate property map with ReactJS's attribute and property mappings
// TODO handle/use .Properties value eg: MUST_USE_PROPERTY is not HTML attr
for (var propname in HTMLDOMPropertyConfig.Properties) {
 if (!HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname)) {
 continue;
 }

 var mapFrom = HTMLDOMPropertyConfig.DOMAttributeNames[propname] || propname.toLowerCase();
}

/**
 * Repeats a string a certain number of times.
 * Also: the future is bright and consists of native string repetition:
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
 *
 * @param {string} string String to repeat
 * @param {number} times Number of times to repeat string. Integer.
 * @see http://jsperf.com/string-repeater/2
 */
function repeatString(string, times) {
 if (times === 1) {
 return string;
 }
 if (times < 0) { throw new Error(); }
 var repeated = '';
 while (times) {
 if (times & 1) {
 repeated += string;
 }
 if (times >>= 1) {
 string += string;
 }
 }
 return repeated;
}

/**
 * Determine if the string ends with the specified substring.
 *
 * @param {string} haystack String to search in
 * @param {string} needle String to search for
 * @return {boolean}
 */
function endsWith(haystack, needle) {
 return haystack.slice(-needle.length) === needle;
}

/**
 * Trim the specified substring off the string. If the string does not end
 * with the specified substring, this is a no-op.
 *
 * @param {string} haystack String to search in
 * @param {string} needle String to search for
 * @return {string}
 */
function trimEnd(haystack, needle) {
 return endsWith(haystack, needle)
 ? haystack.slice(0, -needle.length)
 : haystack;
}

/**
 * Convert a hyphenated string to camelCase.
 */
function hyphenToCamelCase(string) {
 return string.replace(/-(.)/g, function(match, chr) {
 return chr.toUpperCase();
 });
}

/**
 * Determines if the specified string consists entirely of whitespace.
 */
function isEmpty(string) {
 return !/[^\s]/.test(string);
}

/**
 * Determines if the CSS value can be converted from a
 * 'px' suffixed string to a numeric value
 *
 * @param {string} value CSS property value
 * @return {boolean}
 */
function isConvertiblePixelValue(value) {
 return /^\d+px$/.test(value);
}

export class HTMLtoJSX {
 private output: string;
 private level: number;
 private _inPreTag: boolean;


 /**
 * Handles processing of the specified text node
 *
 * @param {TextNode} node
 */
 _visitText = (node) => {
 var parentTag = node.parentNode && node.parentNode.tagName.toLowerCase();
 if (parentTag === 'textarea' || parentTag === 'style') {
 // Ignore text content of textareas and styles, as it will have already been moved
 // to a "defaultValue" attribute and "dangerouslySetInnerHTML" attribute respectively.
 return;
 }

 var text = ''

 if (this._inPreTag) {
 // If this text is contained within a <pre>, we need to ensure the JSX
 // whitespace coalescing rules don't eat the whitespace. This means
 // wrapping newlines and sequences of two or more spaces in variables.
 text = text
 .replace(/\r/g, '')
 .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {
 return '{' + JSON.stringify(whitespace) + '}';
 });
 } else {
 // If there's a newline in the text, adjust the indent level
 if (text.indexOf('\n') > -1) {
 }
 }
 this.output += text;
 }



};

/**
 * Handles parsing of inline styles
 */
export class StyleParser {
 styles = {};
 toJSXString = () => {
 for (var key in this.styles) {
 if (!this.styles.hasOwnProperty(key)) {
 }
 }
 }
}

which is actually a part of a larger file here

With TypeScript nightly we get the following errors:

C:/repos/alm/tests/success/simple/bas.tsx:141 Property 'styles' does not exist on type 'HTMLtoJSX'.
C:/repos/alm/tests/success/simple/bas.tsx:142 Property 'styles' does not exist on type 'HTMLtoJSX'.

Basically this in the class function isn't inferring to StyleParser and instead inferring to HTMLtoJSX

export class StyleParser {
 styles = {};
 toJSXString = () => {
 for (var key in this.styles) {
 if (!this.styles.hasOwnProperty(key)) {
 }
 }
 }
}

Sorry for not being able to narrow it down, deleting portions of the file (e.g. the HTMLtoJSX._visitText method) makes the error go away. Note that this error only appeared in the last 10 days 🌹

[mhegazy]

Nathan Shively-Sanders (@sandersn) can you take a look.

[mhegazy]

possibly caused by #8849

[sandersn]

#8849 contains the only change to checkThisExpression in the last month or two. It's probably the culprit. It now passes /*includeOuterFunctions*/ true to getFlowTypeOfReference. Not sure why this would cause this bug. I'll have to investigate.

[ahejlsberg]

The issue is that the binder is not constructing separate control flows for property initializers. It's an easy fix. I can put up a PR.