Module abi 

Driving the Swift runtime directly: the ABI this crate speaks.

Nothing here goes through a Swift source file. A SwiftUI view is built by finding a mangled symbol with dlsym, arranging registers the way the Swift compiler would have, and branching to it. That works because Swift’s arm64 convention is stable and documented — but three of its registers have no counterpart in a Rust signature, so every call has to be written out:

register	role
x0–x7	integer and pointer arguments, then any generic metadata, then any witness tables
d0–d7	floating-point arguments
x8	address of an indirect (@out) result
x20	the self register: a receiver, or a type’s metadata for an initialiser or static
x21	the error register, which nothing here throws through and everything clobbers

Whether a value travels in a register or by address is the question that decides whether a call works, and it is not visible in the symbol name. A @frozen type of at most four registers is passed directly; a resilient one is passed by address, because the caller is not allowed to know its size. Two traps follow from that and both cost real time here:

• An Optional’s payload is not destructured. Optional<UnitPoint> is two CGFloats and a tag, and it arrives as three integer registers — a Double inside an optional reaches the callee in x0, not d0.
• Getting a return convention wrong rarely faults at the call. A function that writes through x8 while the caller reads x0 hands back a stale register, which SwiftUI stores and dereferences much later.

call holds the primitives that make those choices explicit, and the rest of this module is built on them:

• value — enum tags, optionals, strings and arrays
• metadata — type metadata, witness tables and layout queries
• modifier — applying a View modifier and wrapping the result
• closure — Rust functions Swift can call back into

Re-exports

pub use call::call_f64;

pub use call::call_out;

pub use call::call_regs;

pub use call::call_spilled;

pub use call::ints;

pub use call::static_out;

pub use call::static_regs;

pub use call::Floats;

pub use call::Ints;

Modules

call

Calling into Swift: the two shapes every call takes.

Macros

type_by_name

Resolve a Swift type from its mangled name string.

Structs

ClosureCtx

Context for a Swift () -> T closure implemented in Rust.

FloatClosureCtx

Context for a Swift closure returning a Double.

IndexClosureCtx

Context for a Swift (Int) -> T closure implemented in Rust.

IsolatedContext

The context an @isolated(any) async closure carries.

Pair

Two words, laid out so the ABI returns them in x0 and x1.

PairClosureCtx

Context for a Swift (A, A) -> () closure implemented in Rust.

PairReturnClosureCtx

Context for a Swift closure returning two words.

ValueClosureCtx

Context for a Swift (Value) -> () closure implemented in Rust.

WideClosureCtx

Context for a Swift (V) -> () closure where V may span three registers.

WordClosureCtx

Context for a Swift closure returning a single word.

Functions

anyview_wrap^⚠

Wrap any view value in AnyView.

array_parts^⚠

The elements and count of a Swift Array.

call_modifier^⚠

Apply a View modifier that takes only plain arguments.

call_modifier_d0^⚠

Call a generic View modifier on an AnyView.

call_modifier_generic^⚠

Call a View modifier whose integer arguments are given in full.

copy_value^⚠

Copy a Swift value into uninitialised memory, at +1.

enum_argument^⚠

A no-payload enum’s case, ready to pass in a register.

enum_case_index^⚠

The tag of a payload enum case, by name.

enum_tag^⚠

Which case a multi-payload enum holds.

field_type_metadata^⚠

The metadata of meta’s indexth stored field.

float_closure_thunk^⚠

Address to hand to Swift for a closure returning a Double.

generic_key_argument_count^⚠

How many key arguments a type’s metadata accessor expects.

generic_metadata1^⚠

Call a generic type’s metadata accessor with one key argument.

generic_metadata2^⚠

Call a generic type’s metadata accessor with two key arguments.

generic_metadata_from^⚠

Safety

generic_metadata_from_descriptor^⚠

Instantiate a generic type that exports no metadata accessor.

get_view_wt^⚠

Get the View witness table for a type from the runtime.

get_view_wt_for_proto^⚠

Get a protocol witness table for a type via swift_conformsToProtocol.

index_closure_thunk^⚠

Address to hand to Swift for a one-argument closure.

inject_enum_tag^⚠

Create a Swift.String from a Rust &str, copying the bytes.

mangled_type_name^⚠

The mangled name of whatever meta describes.

metadata0^⚠

Call a metadata accessor that takes no key arguments (a non-generic but resilient type, whose layout is only known at runtime).

pair_closure_thunk^⚠

Address to hand to Swift for a two-argument, no-result closure.

pair_return_closure_thunk^⚠

Address to hand to Swift for a () -> (word, word) closure.

read_enum_tag^⚠

Which case of an enum a value holds.

read_optional_tag^⚠

Which case an Optional<T> holds.

read_swift_string^⚠

Read a Swift String value back into a Rust one.

resolve_type_by_mangled_name^⚠

Safety

set_count^⚠

How many elements a Swift Set holds.

store_optional_tag^⚠

Write Optional<T>’s discriminator into buf.

store_optional_tag_at^⚠

store_optional_tag writing through a raw pointer rather than a slice.

struct_field_offsets^⚠

Where a struct keeps each of its stored properties.

swift_array^⚠

Build a Swift.Array of count elements from raw bytes laid out at the element type’s stride.

swift_closure_thunk^⚠

Address to hand to Swift as the closure function pointer.

swift_set^⚠

Build a Swift Set holding count elements laid out in bytes.

swift_string^⚠

Safety

tuple_element_offsets^⚠

Where each element of a tuple sits inside it.

tuple_metadata^⚠

Build metadata for a tuple of elements.

type_bytes^⚠

How many bytes to allocate for a value of this type.

type_destroy^⚠

Destroy a value in place, through its type’s value witness.

type_size^⚠

Size in bytes of a type, from its value witness table.

type_stride^⚠

Stride in bytes of a type — the spacing between consecutive array elements, which is not the same as its size once alignment padding is involved.

value_closure_thunk^⚠

Address to hand to Swift for a one-argument, no-result closure.

wide_closure_thunk^⚠

Address to hand to Swift for a one-argument, no-result closure whose argument may not fit in a single register.

word_closure_thunk^⚠

Address to hand to Swift for a closure returning one word.