Merge branch 'master' into mappedtype-inference-seperate-symbols

Author: weswigham

.devcontainer/Dockerfile

@@ -0,0 +1,7 @@
+# See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.154.0/containers/javascript-node/.devcontainer/base.Dockerfile
+
+# [Choice] Node.js version: 14, 12, 10
+ARG VARIANT="14-buster"
+FROM mcr.microsoft.com/vscode/devcontainers/javascript-node:0-${VARIANT}
+
+RUN sudo -u node npm install -g gulp-cli

.devcontainer/devcontainer.json

@@ -0,0 +1,16 @@
+{
+    "name": "Node.js",
+    "build": {
+        "dockerfile": "Dockerfile",
+        "args": {
+            "VARIANT": "14"
+        }
+    },
+    "settings": {
+        "terminal.integrated.shell.linux": "/bin/bash"
+    },
+    "extensions": [
+        "dbaeumer.vscode-eslint"
+    ],
+    "remoteUser": "node"
+}

.github/ISSUE_TEMPLATE/Bug_report.md

@@ -4,41 +4,70 @@ about: Create a report to help us improve TypeScript
 title: ''
 labels: ''
 assignees: ''
-
 ---
+# Bug Report
 
-<!-- 🚨 STOP 🚨 STOP 🚨 STOP 🚨
-
-Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Even if you think you've found a *bug*, please read the FAQ first, especially the Common "Bugs" That Aren't Bugs section!
+<!--
+  Please fill in each section completely. Thank you!
+-->
 
-Please help us by doing the following steps before logging an issue:
-  * Search: https://github.com/Microsoft/TypeScript/search?type=Issues
-  * Read the FAQ: https://github.com/Microsoft/TypeScript/wiki/FAQ
+### 🔎 Search Terms
 
-Please fill in the *entire* template below.
+<!--
+  What search terms did you use when trying to find an existing bug report?
+  List them here so people in the future can find this one more easily.
 -->
 
-<!--
-Please try to reproduce the issue with the latest published version. It may have already been fixed.
+### 🕗 Version & Regression Information
+
+<!-- When did you start seeing this bug occur?
+
+"Bugs" that have existed in TS for a long time are very likely to be FAQs; refer to
+  https://github.com/Microsoft/TypeScript/wiki/FAQ#common-bugs-that-arent-bugs
+
+If possible, please try testing the nightly version of TS to see if it's already been fixed.
 For npm: `typescript@next`
 This is also the 'Nightly' version in the playground: http://www.typescriptlang.org/play/?ts=Nightly
+
+Note: The TypeScript Playground can be used to try older versions of TypeScript.
+
+Please keep and fill in the line that best applies:
 -->
-**TypeScript Version:**  3.7.x-dev.201xxxxx
+- This is a crash
+- This changed between versions ______ and _______
+- This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
+- I was unable to test this on prior versions because _______
+
+### ⏯ Playground Link
 
-<!-- Search terms you tried before logging this (so others can find this issue more easily) -->
-**Search Terms:**
+<!--
+  A link to a TypeScript Playground "Share" link which shows this behavior
+
+  The TypeScript Workbench can be used for more complex setups, try
+  https://www.typescriptlang.org/dev/bug-workbench/
+
+  As a last resort, you can link to a repo, but these will be slower for us to investigate.
+-->
+[Playground link with relevant code](https://www.typescriptlang.org/play?#code/PTAEFkE9QYwewCYFNQHM5IM6gBZIE5JA)
 
-**Code**
+### 💻 Code
 
+<!-- Please post the relevant code sample here as well-->
 ```ts
-// A *self-contained* demonstration of the problem follows...
-// Test this by running `tsc` on the command-line, rather than through another build tool such as Gulp, Webpack, etc.
+// We can quickly address your report if:
+//  - The code sample is short. Nearly all TypeScript bugs can be demonstrated in 20-30 lines of code!
+//  - It doesn't use external libraries. These are often issues with the type definitions rather than TypeScript bugs.
+//  - The incorrectness of the behavior is readily apparent from reading the sample.
+// Reports are slower to investigate if:
+//  - We have to pare too much extraneous code.
+//  - We have to clone a large repo and validate that the problem isn't elsewhere.
+//  - The sample is confusing or doesn't clearly demonstrate what's wrong.
 ```
 
-**Expected behavior:**
+### 🙁 Actual behavior
 
-**Actual behavior:**
+<!-- What happened, and why it was wrong -->
 
-**Playground Link:** <!-- A link to a TypeScript Playground "Share" link which demonstrates this behavior -->
+### 🙂 Expected behavior
 
-**Related Issues:** <!-- Did you find other bugs that looked similar? -->
+<!-- What you expected to happen instead, and why -->

.github/ISSUE_TEMPLATE/Feature_request.md

@@ -4,44 +4,56 @@ about: Suggest an idea
 title: ''
 labels: ''
 assignees: ''
-
 ---
+# Suggestion
 
-<!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨
-
-Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker.
-
-Please help us by doing the following steps before logging an issue:
-  * Search: https://github.com/Microsoft/TypeScript/search?type=Issues
-  * Read the FAQ, especially the "Common Feature Requests" section: https://github.com/Microsoft/TypeScript/wiki/FAQ
-
+<!--
+  Please fill in each section completely. Thank you!
 -->
 
-## Search Terms
+## 🔍 Search Terms
 
-<!-- List of keywords you searched for before creating this issue. Write them down here so that others can find this suggestion more easily -->
+<!--
+  💡 Did you know? TypeScript has over 2,000 open suggestions!
+  🔎 Please search thoroughly before logging new feature requests as most common ideas already have a proposal in progress.
+  The "Common Feature Requests" section of the FAQ lists many popular requests: https://github.com/Microsoft/TypeScript/wiki/FAQ#common-feature-requests
 
-## Suggestion
+  Replace the text below:
+-->
 
-<!-- A summary of what you'd like to see added or changed -->
+List of keywords you searched for before creating this issue. Write them down here so that others can find this suggestion more easily and help provide feedback.
 
-## Use Cases
+## ✅ Viability Checklist
 
 <!--
-What do you want to use this for?
-What shortcomings exist with current approaches?
+   Suggestions that don't meet all these criteria are very, very unlikely to be accepted.
+   We always recommend reviewing the TypeScript design goals before investing time writing
+   a proposal for ideas outside the scope of the project.
 -->
-
-## Examples
-
-<!-- Show how this would be used and what the behavior would be -->
-
-## Checklist
-
 My suggestion meets these guidelines:
 
 * [ ] This wouldn't be a breaking change in existing TypeScript/JavaScript code
 * [ ] This wouldn't change the runtime behavior of existing JavaScript code
 * [ ] This could be implemented without emitting different JS based on the types of the expressions
-* [ ] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
+* [ ] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
 * [ ] This feature would agree with the rest of [TypeScript's Design Goals](https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals).
+
+
+## ⭐ Suggestion
+
+<!-- A summary of what you'd like to see added or changed -->
+
+## 📃 Motivating Example
+
+<!--
+  If you were announcing this feature in a blog post, what's a short explanation that shows
+  a developer why this feature improves the language?
+-->
+
+## 💻 Use Cases
+
+<!--
+  What do you want to use this for?
+  What shortcomings exist with current approaches?
+  What workarounds are you using in the meantime?
+-->

.github/ISSUE_TEMPLATE/lib_change.md

@@ -0,0 +1,55 @@
+---
+name: Library change
+about: Fix or improve issues with built-in type definitions like `lib.dom.d.ts`, `lib.es6.d.ts`, etc.
+title: ''
+labels: ''
+assignees: ''
+---
+# lib Update Request
+
+<!--
+  Please fill in each section completely. Thank you!
+
+  Are you here for one of these commonly-requested lib changes?
+    * Object.keys - see https://stackoverflow.com/questions/55012174/
+    * Array methods - see https://github.com/microsoft/TypeScript/issues/36554
+    * parseInt, parseFloat, isFinite, isNaN, etc. - see https://github.com/microsoft/TypeScript/issues/4002
+
+  The DOM lib is maintained elsewhere and you can skip a step by filing issues/PRs for the DOM at that repo.
+  See https://github.com/microsoft/TypeScript-DOM-lib-generator
+-->
+
+## Configuration Check
+
+<!--
+  If you're missing common new methods like Array.includes, you may have a misconfigured project.
+  Try setting `lib: "es2020"` and checking whether the type you want is present.
+  You can diagnose further by running `tsc` with `--listFilesOnly` or `--showConfig`.
+
+  Conversely, if you are seeing built-in methods you expect to *not* see, check your 'lib' setting
+  or review your dependencies for lib/reference directives that might be polluting
+  your global scope. This is common when using the 'node' type library. See https://github.com/microsoft/TypeScript/issues/40184
+
+  Replace the text below:
+-->
+My compilation *target* is `ES2015` and my *lib* is `the default`.
+
+## Missing / Incorrect Definition
+
+<!--
+  What property, method, function, etc is missing or incorrect?
+-->
+
+## Sample Code
+
+<!--
+  What's some code using this that should work, but doesn't?
+-->
+
+## Documentation Link
+
+<!--
+  Link to relevant documentation (e.g. MDN, W3C, ECMAScript Spec) to consult for this property.
+  Note that lib.dom.d.ts intentionally does not include browser-specific extensions
+   or early experimental features.
+-->

.github/workflows/new-release-branch.yaml

@@ -22,7 +22,7 @@ jobs:
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' src/compiler/corePublic.ts
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' tests/baselines/reference/api/typescript.d.ts
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' tests/baselines/reference/api/tsserverlibrary.d.ts
-        sed -i -e 's/const version = `${versionMajorMinor}.0-.*`/const version = `${versionMajorMinor}.0-${{ github.event.client_payload.core_tag || 'dev' }}`/g' src/compiler/corePublic.ts
+        sed -i -e 's/const version\(: string\)\{0,1\} = `${versionMajorMinor}.0-.*`/const version = `${versionMajorMinor}.0-${{ github.event.client_payload.core_tag || 'dev' }}`/g' src/compiler/corePublic.ts
         npm ci
         gulp LKG
         npm test

.github/workflows/set-version.yaml

@@ -28,7 +28,7 @@ jobs:
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' src/compiler/corePublic.ts
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' tests/baselines/reference/api/typescript.d.ts
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' tests/baselines/reference/api/tsserverlibrary.d.ts
-        sed -i -e 's/const version = .*;/const version = "${{ github.event.client_payload.package_version }}" as string;/g' src/compiler/corePublic.ts
+        sed -i -e 's/const version\(: string\)\{0,1\} = .*;/const version = "${{ github.event.client_payload.package_version }}" as string;/g' src/compiler/corePublic.ts
         npm ci
         gulp LKG
         npm test

.gitignore

@@ -85,6 +85,7 @@ tests/baselines/reference/dt
 .failed-tests
 TEST-results.xml
 package-lock.json
+tests/cases/user/npm/npm
 tests/cases/user/TypeScript-React-Starter/TypeScript-React-Starter
 tests/cases/user/TypeScript-Node-Starter/TypeScript-Node-Starter
 tests/cases/user/TypeScript-React-Native-Starter/TypeScript-React-Native-Starter

.npmignore

@@ -10,6 +10,7 @@ scripts
 src
 tests
 Jakefile.js
+.devcontainer
 .eslintrc
 .eslintignore
 .editorconfig

.travis.yml

@@ -70,6 +70,13 @@ In general, things we find useful when reviewing suggestions are:
 
 ## Tips
 
+### Using a development container
+
+This repository includes a [development container](https://code.visualstudio.com/docs/remote/containers) that you can use to quickly create an isolated development environment with all the tools you need to start working on TypeScript. To get started with a dev container and VS Code, either:
+
+- Clone the TypeScript repository locally and use the `Open Folder in Container` command.
+- Use the `Clone Repository in Container Volume` command to clone the TypeScript repository into a new container.
+
 ### Faster clones
 
 The TypeScript repository is relatively large. To save some time, you might want to clone it without the repo's full history using `git clone --depth=1`.
@@ -153,17 +160,17 @@ gulp runtests --tests=2dArrays
 
 ## Debugging the tests
 
-You can debug with VS Code or Node instead with `gulp runtests --inspect`:
+You can debug with VS Code or Node instead with `gulp runtests -i`:
 
 ```Shell
-gulp runtests --tests=2dArrays --inspect
+gulp runtests --tests=2dArrays -i
 ```
 
 You can also use the [provided VS Code launch configuration](./.vscode/launch.template.json) to launch a debug session for an open test file. Rename the file 'launch.json', open the test file of interest, and launch the debugger from the debug panel (or press F5).
 
 ## Adding a Test
 
-To add a new test case, add a `.ts` file in `tests\cases\compiler` with code that shows the your bug is now fixed, or your new feature now works.
+To add a new test case, add a `.ts` file in `tests\cases\compiler` with code that shows the bug is now fixed, or your new feature now works.
 
 These files support metadata tags in the format  `// @metaDataName: value`.
 The supported names and values are the same as those supported in the compiler itself, with the addition of the `fileName` flag.
@@ -189,16 +196,25 @@ import { f as g } from "file1";
 var x = g();
 ```
 
-## Managing the Baselines
+## Managing the baselines
 
-Compiler tests generate baselines: one file each for the emitted `.js`, the errors produced by the compiler, the type of each expression, and symbol for each identifier. Additionally, some tests generate baselines for the source map output.
+Most tests generate "baselines" to find differences in output.
+As an example, compiler tests usually emit one file each for
+
+- the `.js` and `.d.ts` output (all in the same `.js` output file),
+- the errors produced by the compiler (in an `.errors.txt` file),
+- the types of each expression (in a `.types` file),
+- the symbols for each identifier (in a `.symbols` file), and
+- the source map outputs for files if a test opts into them (in a `.js.map` file).
 
 When a change in the baselines is detected, the test will fail. To inspect changes vs the expected baselines, use
 
 ```Shell
-gulp diff
+git diff --diff-filter=AM --no-index ./tests/baselines/reference ./tests/baselines/local
 ```
 
+Alternatively, you can set the `DIFF` environment variable and run `gulp diff`, or manually run your favorite folder diffing tool between `tests/baselines/reference` and `tests/baselines/local`. Our team largely uses Beyond Compare and WinMerge.
+
 After verifying that the changes in the baselines are correct, run
 
 ```Shell