♻️ Enable TS type-checking on #core/assert

[rcebulko]

TS supports type narrowing via type assertions, but does so in a way that is mutually exclusive with type-checking a returned value. See microsoft/TypeScript#34636 and microsoft/TypeScript#40562

Workaround: Type-checking for now will support assertion format, but code itself will still return the asserted values as normal (by casting to void). This means that as code is migrated to pass type-checking, it'll have to update how it calls these assertion functions, but any existing code relying on the return pattern will continue to function as normal.

Explanation of why this is annoying/doesn't fit both use-cases:

/** @return {x is Element} */
function isElement(x) { ... }

/** @return {asserts x is Element} */
function assertElement(x) { ... }

// The first mostly helps in conditionals like
if (isElement(e)) {
  e.getAttribute('foo'); // this is fine, because isElement "returns true iff e is Element"
}

assertElement(bar);
bar.getAttribute('foo'); // this is fine, because assertElement "asserts bar is Element"

// this can't work in TS, because any assertion return type is equivalent to void
assertElement(bar).getAttribute('foo');

[amp-owners-bot]

Hey @jridgewell! These files were changed:

src/core/3p-frame-messaging.js
src/core/amp-config.extern.js
src/core/assert.shame.d.ts
src/core/assert/base.js
src/core/assert/dev.js
src/core/assert/error.d.ts
src/core/assert/index.js
src/core/assert/user.js
src/core/dom/index.js
src/core/dom/jsx.js
src/core/dom/layout/intersection-no-root.js
src/core/dom/layout/intersection.js
+9 more

[samouri]

Didn't we discuss preferring T[] vs. Array

Suggested change

	* @param {Array<*>|string=} opt_message The assertion message
	* @param {any[]|string=} opt_message The assertion message

[rcebulko]

1. I'm not positive if any works in JSDoc comments 2) Yes, I agree, but also I haven't been updating it everywhere. Would prefer to set up TSLint and let it do it for us

[samouri]

1. any does work
2. makes sense, especially if its auto-fixable.

[samouri]

nit: does this work:

'#core': ['.']
'#core/*': ['./*']

[rcebulko]

It will once context is allowed (yes we could exclude context directly instead). That's where we'll be very soon.