close some gaps in the type system

LANGUAGE.md

@@ -41,7 +41,7 @@ roadmap and milestone history.
 - source-order native structs, opaque nominal records with `Name :: opaque`, complete `c_struct { ... }`, keyed record literals, native untagged unions, and native tagged unions `union(Enum)` / `union(enum)`
 - named native struct fields may declare defaults with `field T = expression`; keyed literals use defaults for omitted fields and explicit initializers override them
 - void-payload tagged-union variants, anonymous struct payloads, contextual `.variant`, `.variant{payload}`, and `.variant{field = value}` construction
-- native sum composition with `A | B` for unbacked enums and tagged unions, using program-global `u16` variant ids
+- native sum composition with `A | B` for unbacked enums and tagged unions, optionally grouped as `(A | B)`, using program-global `u16` variant ids
 - fallible channel types `T ! E`, where `E` is a native enum/tagged union or supported sum composition; `void ! E` functions complete successfully on fallthrough, and void-success `catch` handlers may fall through without `yield`
 
 #### native record constraint fields
@@ -98,7 +98,7 @@ fields. `_` is not a keyword member name.
 - `for` loops over ranges, arrays, slices, and pointers-to-arrays with copy captures, pointer captures `|@item|`, and optional `usize` index captures; `expand for` specializes a comptime aggregate into one checked body per element
 - `break`, `continue`, labeled `break :label`, labeled `continue :label`, and labeled plain blocks; `break :label` can cross nested scopes to exit a labeled block
 - bare block scopes, `defer`, and fallible-function `errdefer` with optional error capture; cleanup is block-scoped and LIFO
-- bare void `return`, same-line `return value`, value blocks, value `if`, value loops, value `match`, and strictly value-producing `yield value` / `yield :label value`
+- bare void `return`, same-line `return value`, value blocks, value `if` with implicit single-expression branches, value loops, value `match`, and strictly value-producing `yield value` / `yield :label value`
 - `match` statements/expressions over enums, tagged unions, and scalars, including exhaustiveness checks, payload captures, pointer payload captures, multi-pattern arms, and scalar range patterns
 - a final `expand |value|:` enum arm or `expand |payload[, tag]|:` tagged-union arm generates one specialized arm for each variant not covered earlier; enum values and optional tags are comptime-known, while union payloads keep their concrete variant type
 - fallible `try`, fallback `catch`, and `catch |e| { ... }` handler blocks
@@ -188,7 +188,7 @@ as `math.divfloor(a, b)` resolve to ordinary functions.
 - comptime parameters may appear anywhere, are erased from the runtime ABI, and accept recursively stable booleans, integers, floats, types, immutable bytes, enums, fixed arrays, records/tuples, optionals, tagged unions, and bare function identities; equal structural values and aliases of one function declaration share specializations, while distinct declarations remain distinct and pointers, general slices, fallibles, ranges, untagged unions, and undefined values have no stable comptime identity
 - comptime parameters may be omitted when uniquely recoverable from runtime arguments, the immediate expected result, or exact type-factory provenance; `_` is an explicit inference hole
 - forced typed comptime expressions such as `$sum(1, 2)`, `$Point { x = 1, y = 2 }`, and comptime value blocks such as `${ yield 4 }`
-- comptime execution for bodyful Brolang functions with mutable locals, loops, `defer`, `match`, `try`/`catch`, pointer/slice storage mutation, pointer captures, and calls through comptime-known function values; `undefined` storage may be initialized at comptime, but remaining poison cannot be observed
+- comptime execution for bodyful Brolang functions with mutable locals, loops, `defer`, `match`, `try`/`catch`, exact type `==`/`!=`, pointer/slice storage mutation, pointer captures, and calls through comptime-known function values; `undefined` storage may be initialized at comptime, but remaining poison cannot be observed
 - comptime type factories such as `Box func($T type) type { return struct { value T } }`; calls like `Box(i32)` are concrete nominal types and may appear anywhere a type is expected
 - tuple types are unnamed-field structs (`struct { i32, []u8 }`), tuple values use `{1, "bro"}` / `{1,}` / `{}`, and fields use canonical numeric names such as `.0`
 - `typeinfo!`, `field!`, `compile_error!`, and semantic `expand for` provide compile-time record and enum reflection and heterogeneous static expansion without runtime metadata; enum reflection exposes declaration-ordered fields, reflected aggregates remain persistent compile-time values, and expand-loop `break` / `continue` must be selected entirely at comptime
@@ -216,7 +216,7 @@ as `math.divfloor(a, b)` resolve to ordinary functions.
 - `std/io` explicit `Io` capabilities, provider-bound `Reader`/`Writer` handles, existing-file open/close operations, allocation-free `write_all`, and comptime-expanded writer-first `print`; formatting supports natural `{}`, byte `{s}`, decimal `{d}`, integer `{b}` / `{o}` / `{x}` / `{X}`, byte-character `{c}`, scientific float `{e}`, and `{{` / `}}`, with malformed formats and incompatible tuple fields rejected at comptime
 - entry points are either `main func() ...` or `main func(init process.Init) ...`; `std/process.Init` carries startup capabilities, currently only `io`, while the system provider remains hidden inside `std/io`
 - `std/debug.print` is an allocation-free, failure-ignoring stderr escape hatch independent of `process.Init`
-- `std/testing` supplies fallible `expect` and expected-first `expect_equal`; direct calls through
+- `std/testing` supplies fallible `expect`, expected-first `expect_equal`, and exact compile-time `expect_type`; direct calls through
   an alias of exactly `@std/testing` receive compiler-injected source locations
 
 ### compiler behavior