Rust: Type inference and path resolution for builtins

[hvitved]

Follows up on #19421, and adds type inference and path resolution for builtins.

DCA confirms that we gain additional call edges, without significant performance impact.

[paldepind]

Really amazing to get types for builtins! 🤩

When I run the tests I get a lot of errors of the form:

Location is outside of test directory: file:///BUILTINS/types.rs:8:1:8:15

Do we have to live with those or is there some workaround? Maybe transforming the path a bit?

[paldepind]

It would be nice to turn these 5 lines into let ... = ... expressions and add inline expectations as above.

[paldepind]

Maybe add a comment as for why we're doing this? Is it only to make things look cleaner in the .expected file?

[hvitved]

It is because the actual file path points to the folder containing the extractor, so it is very much environment dependent.

[paldepind]

Given that the Rust type is written as one word in all lower-case (and not something like iSize or i_size) I'd expect the the QL name to be Isize? Same for usize above.

[paldepind]

Here's an idea for a simple refactor. It factors out the repeated TStruct and the repeated n.getSuffix() logic.

Note that this requires getSuffix to be an abstract predicate on NumberLiteralExpr which makes sense as all the extensions have that predicate.

Suggested change

	pragma[nomagic]
	StructType getBuiltinType(string name) {
	result = TStruct(any(Builtins::BuiltinType t | name = t.getName()))
	}
	pragma[nomagic]
	private StructType inferLiteralType(LiteralExpr le) {
	le instanceof CharLiteralExpr and
	result = TStruct(any(Builtins::Char t))
	or
	le instanceof StringLiteralExpr and
	result = TStruct(any(Builtins::Str t))
	or
	le =
	any(IntegerLiteralExpr n |
	not exists(n.getSuffix()) and
	result = getBuiltinType("i32")
	or
	result = getBuiltinType(n.getSuffix())
	)
	or
	le =
	any(FloatLiteralExpr n |
	not exists(n.getSuffix()) and
	result = getBuiltinType("f32")
	or
	result = getBuiltinType(n.getSuffix())
	)
	or
	le instanceof BooleanLiteralExpr and
	result = TStruct(any(Builtins::Bool t))
	}
	pragma[nomagic]
	private StructType inferLiteralType(LiteralExpr le) {
	exists(Builtins::BuiltinType t | result = TStruct(t) |
	le instanceof CharLiteralExpr and
	t instanceof Builtins::Char
	or
	le instanceof StringLiteralExpr and
	t instanceof Builtins::Str
	or
	le =
	any(NumberLiteralExpr ne |
	t.getName() = ne.getSuffix()
	or
	not exists(ne.getSuffix()) and
	(
	ne instanceof IntegerLiteralExpr and
	t instanceof Builtins::I32
	or
	ne instanceof FloatLiteralExpr and
	t instanceof Builtins::F64
	)
	)
	or
	le instanceof BooleanLiteralExpr and
	t instanceof Builtins::Bool
	)
	}

[hvitved]

Do we have to live with those or is there some workaround? Maybe transforming the path a bit?

Yeah, we have to live with those, or alternatively show no file path at all.