# "quick" / "easy" fixes

- for global initialization cycles, report also starting and ending lines

# milestones

1. interop type foundation (implemented)
   - unsigned integers, floats, and target-dependent c scalar types
   - atomic `c_*` primitive types remain distinct until target-aware lowering
   - `c_func` and pointer-only `c_struct`; `c` remains an ordinary identifier
   - keep binding mutability (`::` / `=`) separate from element or pointee mutability (`mut`)
   - arrays and indexing
     - `[N]T`: array with `N` logical elements
     - `[N;S]T`: array with `N` logical elements followed by sentinel `S`
   - pointers
     - `@T` / `@mut T`: non-null single-item pointer without arithmetic
     - `*T` / `*mut T`: non-null many-item pointer with arithmetic
     - optional pointers represent nullable pointers (i.e. `?@T` / `?@mut T`, `?*T` / `?*mut T`)
   - slices and slicing
     - `[]T`: pointer and length
     - `[;S]T`: pointer and length with a sentinel invariant
     - ordinary slices do not guarantee null termination
   - string literals as immutable sentinel slices backed by static arrays (superseded by milestone 3.5)
   - character literals
   - optionals with trapping unwrap and fallback operations
   - native structs with compiler-controlled layout
   - pointer-only `c_struct` support with target c layout
     - `Some :: c_struct { ... }`: defined c-layout struct
     - `Some :: c_struct`: opaque c-layout struct
     - passing c structs by value was deferred until milestone 4.1

2. restricted c header imports (implemented)
   - treat an imported header as a synthetic, file-local package namespace
     - `native :: import "relative/path/to/header.h"`
   - import functions, typedefs, scalar types, and pointers to opaque records
   - keep implementation linking separate from header imports
   - cache imports by canonical header path and target/include/define configuration
   - diagnose unsupported declarations when referenced
   - dynamically load libclang behind a replaceable c importer boundary

3. c variadic calls (implemented)
   - represent c variadics as a fixed parameter count plus a variadic flag
   - apply c default argument promotions at call sites
   - emit LLVM c-variadic declarations and calls
   - keep native brolang variadics and tuple design separate

3.5. sentinel pointers and c strings (implemented)
   - add sentinel many-item pointers: `[*;S]T`
   - represent string literals as immutable pointers to statically stored sentinel arrays: `@[N;0]u8`
   - arrays expose `.len` but no `.ptr`; slices and pointers-to-arrays expose sentinel-preserving `.ptr`
   - allow pointer-to-array `.len`, indexing, slicing, pointer decay, and slice construction without explicit dereference
   - preserve or forget sentinel information through compatible pointer and slice coercions without copying arrays
   - allow zero-terminated immutable byte pointer views to convert to immutable `*c_char` and `[*;0]c_char`
   - keep `u8` and `c_char` distinct to preserve target-dependent scalar c semantics
   - reject general `u8`/`c_char` interchange, slice-to-pointer coercion, and conversion to mutable c character pointers

4. advanced c interop
   - by-value records and unions (implemented)
     - complete plain imported structs/unions and manual `c_struct` values
     - fixed C arrays inside imported records
     - keyed struct literals and exactly-one-field union literals
     - field reads/writes, storage, and fixed-signature calls/returns
     - aarch64-macos small aggregate, homogeneous float aggregate, and indirect ABI lowering
     - keep incomplete, bitfield, packed, flexible-array, qualified-field, and otherwise non-plain records pointer-only
     - keep C variadic record arguments unsupported
   - function pointers and callbacks (implemented)
     - imported C function pointer typedefs lower to nullable pointer types
     - manual `?*c_func(...) T` callback type spelling
     - concrete `c_func` declarations/definitions can be passed as callback values
     - postfix calls through non-null function pointers, including `callback?(...)`
     - fixed and C-variadic callback ABI emission through LLVM indirect calls
   - external variables
   - macros and static inline functions
   - exporting brolang functions to c