Make-green half of the cadence step started in A1. Wires the
`#selector` directive end-to-end:
- Lexer token `hash_selector` at src/token.zig + lookup row in
src/lexer.zig.
- AST field `selector_override: ?[]const u8 = null` on
`ForeignMethodDecl` (src/ast.zig).
- Parser block in src/parser.zig that mirrors
`#jni_method_descriptor` — both occupy the same slot after the
optional `-> ReturnType` and before the body/terminator. Not
mutually exclusive at parse time.
- LSP semantic-token list (src/lsp/server.zig) updated.
- Lowering: `deriveObjcSelector` returns
`{ sel, keyword_count, is_override }`. When `is_override` is true,
the selector string is the user's literal and `keyword_count` is
the colon count in that literal. Both `lowerObjcMethodCall` and
`lowerObjcStaticCall` use the result.
Diagnostic policy when override colon-count ≠ call arity:
- Default mangling path: stays an error (`.err`). The user can fix
the sx-side name to produce the right keyword count.
- Override path: downgrades to a warning (`.warn`). Rationale:
Obj-C's `objc_msgSend` doesn't validate colon-vs-arg the way JNI's
`GetMethodID` validates the descriptor — the runtime dispatches
regardless and the wrong-arity case becomes silent calling-
convention corruption. The compiler is the last line of defense
for this typo class, but the warning preserves the override's
escape-hatch character (deliberate mismatches still proceed).
Snapshot for `examples/ffi-objc-dsl-06-selector-override.sx` flips
from the pre-3.2 parser-error to working output:
static override non-null: true
The mismatch diagnostic text in
`examples/ffi-objc-dsl-04-mismatch.sx`'s snapshot is updated to
drop the "once that lands (3.2)" phrasing now that 3.2 is here.
165/165 example tests.
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