CodeQL: Support multiple types for `instanceof`

[Marcono1234]

Currently instanceof only supports a single type as right operand. This can make its usage quite verbose when multiple alternative type checks have to be performed. For example search in the CodeQL source with the following Regex (increasing or decreasing the number in {3,} to find longer or shorter chains):

(.+) instanceof [a-zA-Z]+([\s\n]+or[\s\n]+\1 instanceof [a-zA-Z]+){3,}

This finds for example:

• codeql/java/ql/lib/semmle/code/java/ControlFlowGraph.qll

  Lines 441 to 451 in 3119885

  	this instanceof ReturnStmt
  	or
  	this instanceof ThrowStmt
  	or
  	this instanceof Literal
  	or
  	this instanceof TypeLiteral
  	or
  	this instanceof ThisAccess
  	or
  	this instanceof SuperAccess

• codeql/java/ql/lib/semmle/code/java/JDK.qll

  Lines 157 to 161 in 3119885

  	this instanceof PrimitiveType or
  	this instanceof NullType or
  	this instanceof VoidType or
  	this instanceof BoxedType or
  	this instanceof TypeString

Would it be possible to allow multiple types for the instanceof expression? The syntax could be similar to a set literal, also allowing a trailing comma (except that currently a set literal is defined as expression, so it would not be valid for types), for example:

this instanceof [PrimitiveType, NullType, VoidType, BoxedType, TypeString]

[smowton]

Thanks for the suggestion, we'll take it under consideration :)

[Marcono1234]

Thanks!

Where is the preferred place to post such CodeQL language suggestions, and in which form (issue or discussion) do you prefer them? Currently there are still some in the github/codeql-cli-binaries repository, but there are also two (empty) discussions here in this repository (#5348 and #5573).

[smowton]

This repo is best for such things. Those two are both also good suggestions btw, thanks for raising them too.