feat: support boolean conditional expressions

README.md

@@ -200,6 +200,8 @@ enums use `Kind :: enum { number, empty }`, qualified members such as `Kind.numb
 
 untagged `Bits :: union { integer u64, real f64 }` overlays its members in shared storage. keyed construction selects exactly one member; reading another member reinterprets the same bytes. tagged unions use `union(enum)` or `union(Kind)`; an explicit enum must contain every union variant. construct them with `Choice { number = 42 }`, contextual `.number{42}`, `.point{x = 40, y = 2}` for record payloads, or `.empty` for `void` payloads. field reads/writes validate the active tag. nested aggregates copy by value, including across calls. CLI union results print `{payload}` (or `{}` for a void payload); untagged results print the first member.
 
+`if (guard) then_value else else_value` is a boolean value expression. the guard runs once and only the selected expression executes; `else` is required and binds to the nearest conditional. both runtime branches must fit the result context, including optional/fallible channels and aggregate copies. constant-input procedures, direct `$()` evaluation, generic branch specialization and generated type positions reuse checked match execution. guards require parentheses unless they are calls or explicit `$()` expressions. parenthesize a conditional used as a match-arm value to distinguish it from an `if` statement. optional payload captures and yielding value blocks remain unsupported.
+
 `match value { .number |n|: n + 2, .empty: 0 }` selects one arm after evaluating its subject once. matches support enums, tagged unions, composed error sets, numeric/boolean scalars, comma-separated patterns, numeric ranges, final `else` arms, arm-local payload captures, statement bodies and expression results. checking rejects missing coverage, duplicate/overlapping patterns, unreachable arms and incompatible captures/results. block arms can return or transfer loop control; yielding value blocks and pointer captures belong to later gates.
 
 a final `inline |tag|:` arm on an enum, or `inline |payload[, tag]|:` on a tagged union, expands into one ordinary arm for each variant not covered earlier. dispatch remains runtime and evaluates the subject once. enum captures and optional union tags are immutable compile-time enum values; payloads are immutable by-value captures with each variant's exact type, including a `void` value for empty variants. either capture may be discarded with `_`. static tag matches/conditions select variant-specific operations before checking, including generic calls, nested inline arms and type-producing procedure bodies. ordinary payloads remain runtime values, and return/break/continue/deferred cleanup retain ordinary match semantics. redundant/nonfinal inline arms, invalid captures and scalar/untagged subjects are diagnosed. expansion shares the 4096-step type-control bound.