Support Swift.Array in Embedded Swift

[adrian-prantl]

No description provided.

[augusto2112]

Thanks for doing this!

[augusto2112]

I understand that you need this because we might not have debug info for a typealias declared inside a substituted generic type.

But instead of finding the parent and looking for the typealias as one of it's children, would it be possible instead to:

• Map the generic typealias out of context first (we'd need to add a new function for this).
• Look up the mapped out typealias directly.

So if we're looking for the typealias [Int]._Buffer (mangled name $eSa7_BufferaySi_GD), we'd first map that out of context [τ_0_0]._Buffer (mangled name $eSa7_Bufferayx_GD), and FindTypes should be able to find this in DWARF directly.

This would support typealias declared at greater depths than 1.

We could do it as a follow up patch though since this one is already quite big.

[adrian-prantl]

Map the generic typealias out of context first (we'd need to add a new function for this).

Do we have enough info to do this? We know what the linearization of the substitutions is, but we don't know the depth of any of the parameters. Is that something we could reconstruct from what we have in DWARF today?

[augusto2112]

I think so. I'm looking at the debug info for this program:

struct A<T> {
    struct B<U, V> {
        struct C<W> {
                let t: T
                let u: U
                let v: V
                let w: W
        }
    }
}

func f() {
    let c = A<Int>.B<Double, Float>.C<String>(t: 4, u: 4.2, v: 4.2, w: "Hi")
}
f()

The specification of C for c is:

0x00000736:         DW_TAG_structure_type
    DW_AT_specification	(0x000006f4 "$e1a1AV1BV1CVyx_qd__qd_0__qd0__GD")
    0x0000073f:           DW_TAG_member
        DW_AT_type	(0x00000746 "a::$e1a1AVyxGD::$e1a1AV1BVyx_qd__qd_0_GD::$e1a1AV1BV1CVySi_SdSf_SSGD<Swift::String, Swift::Double, Swift::Float, Swift::Int>")

(This debug info looks pretty odd and very redundant, we should change what the compiler emits to cut down on the useless information).

$e1a1AV1BV1CVySi_SdSf_SSGD demangles to:

➜  lldb-macosx-arm64 xcrun swift-demangle e1a1AV1BV1CVySi_SdSf_SSGD
$e1a1AV1BV1CVySi_SdSf_SSGD ---> a.A<Swift.Int>.B<Swift.Double, Swift.Float>.C<Swift.String>

The debug info for C (unsubstituted is):

0x000006f4:         DW_TAG_structure_type
                      DW_AT_name	("C")
                      DW_AT_linkage_name	("$e1a1AV1BV1CVyx_qd__qd_0__qd0__GD")

$e1a1AV1BV1CVyx_qd__qd_0__qd0__GD demangles to:

➜  lldb-macosx-arm64 xcrun swift-demangle e1a1AV1BV1CVyx_qd__qd_0__qd0__GD
$e1a1AV1BV1CVyx_qd__qd_0__qd0__GD ---> a.A<A>.B<A1, B1>.C<A2>

So it should be doable.

[adrian-prantl]

@swift-ci test

[adrian-prantl]

@swift-ci test

[adrian-prantl]

@swift-ci test

[adrian-prantl]

@swift-ci test