* Check to make sure default npm exists at path before trying to use it
**Bug**
If the typings installer is run under a copy of node that does not include npm—but on a machine that does have npm installed—it will incorrectly try to use the npm that does not exist next to its running version of node
**Fix**
Make sure that we check that npm we select exists before trying to use it as the default. Otherwise, fall back to using plain old `npm`
* Add command line flag to gate new behavior
* Fix missing semicolon
* Scan backticks in jsdoc as a single token less often
Previously, matching backticks in jsdoc would always be scanned as one
token to aid parsing incorrect jsdoc that uses backticks for parameter
names:
``js
/** @param {string} `nope`
* @param {number} `not needed`
*/
```
However, this is wrong for code fences, which use triple backticks. This
fix parses a single backtick as a single token if it's immediately
followed by another backtick or by a newline. It retains the
questionable tokenisation of backticks-as-pairs in other cases, however.
A better fix might be to have the parser ignore backticks in jsdoc
instead.
* Add test case
* Handle jsdoc backticks in the parser, not scanner
Previously, the jsdoc scanner had ad-hoc handling of backticks that was
similar in structure to the normal scanner's handling, but much simpler.
This was a smaller code change, but is handled backwards: the special
case of backtick-quoted parameter names was handled in the scanner
instead of in the jsdoc identifier parsing code. That made it overapply
and block correct handling of asterisks across newlines, which was most
obvious in code fences inside jsdoc, as in #23517.
Fixes#23517
* More cleanup
* Perform excess property checking on intersection and union members
* Allow partial union props to contain the undefined type
* Add test case from #30771
* Un-terse getPossiblePropertiesOfUnionType side-effecting code
* Fix bug exposed in RWC
* Cache results of getPossiblePropertiesOfUnionType
* Fix whitespace
