pub struct S<const N: usize> {
pub x: [u32; N]
}
pub fn f(y: [u32; 1]) -> S<1> {
S { x: y }
}
pub fn g(y: [u32; 2]) -> S<2> {
S { x: y }
}
The f and g functions return two different instantiations of the S struct. While S<1> and S<2> look distinct at the source level, they are not so distinct at the MIR level:
Both occurrences of S are represented as ADTs with their const parameter instantiated with nonty::Const. This is a challenge for tools like SAW, which look up ADTs in a type-directed way. One might imagine writing something like this to look up S<1> or S<2>:
mir_find_adt m "test::S" [mir_const];
Where mir_const represents nonty::Const. The problem is that this is ambiguous, as it could refer to bothS<1> and S<2>. Moreover, the JSON doesn't provide a straightforward way to tell which ADT was instantiated with <1> and which was instantiated with <2>.
I propose that we change the representation of nonty::Const to also include the particular constant that was used for the instantiation. That way, SAW users could write something like:
mir_find_adt m "test::S" [mir_const {{ 1 }}];
mir_find_adt m "test::S" [mir_const {{ 2 }}];
MIR's GenericArgKind::Const should provide all the information necessary to encode this constant information.
Consider this code:
The
fandgfunctions return two different instantiations of theSstruct. WhileS<1>andS<2>look distinct at the source level, they are not so distinct at the MIR level:Both occurrences of
Sare represented as ADTs with their const parameter instantiated withnonty::Const. This is a challenge for tools like SAW, which look up ADTs in a type-directed way. One might imagine writing something like this to look upS<1>orS<2>:Where
mir_constrepresentsnonty::Const. The problem is that this is ambiguous, as it could refer to bothS<1>andS<2>. Moreover, the JSON doesn't provide a straightforward way to tell which ADT was instantiated with<1>and which was instantiated with<2>.I propose that we change the representation of
nonty::Constto also include the particular constant that was used for the instantiation. That way, SAW users could write something like:MIR's
GenericArgKind::Constshould provide all the information necessary to encode this constant information.