A while loop's counter gets an integer range when the loop only adds
positive literals to it and its condition bounds it. A counter written
inside a nested loop was refused, which is every hand-written scanner:
`while (pos < end) { ... while (pos < end && isDigit(...)) pos++; ... }`.
A nested while loop may now advance the counter when its own condition
bounds it the same way and does not write it. Its passes start at most
at that bound, so it leaves the counter at its entry value or at the
highest value one of its passes reaches, and the outer loop's range
follows from there. Other nested loops, and nested loops that do not
bound the counter, still refuse it.
An array constructed with a known element count of up to 16 (array
literals, copies, slices and the arrays the runtime builds) keeps its
slots in its own block, as empty arrays built for appends already do, so
it costs one allocation and one free.
scr_arr_make_ops is inlined into its two constructors, so the size class
of scr_arr_new_ops_small folds to a table index. It writes the element
ops id with the other header fields and records ops past the registry
in the array's ext after the storage is set up: the ext pointer precedes
the dense allocation, so inline slots must move out before the ext is
created.
A class carries the collector header when any class in its hierarchy can
be on a cycle, so instances of classes whose own fields hold nothing
cycle-capable were buffered as candidates and walked by every level. Such
an object has no traced children and is never on a cycle.
Their descriptors now name scr_cyc_no_children, and they are allocated
with buf set to SCR_CYC_ACYCLIC. That value has the buffered bit set, so
a release that leaves the object alive makes no call; scr_cyc_is_buffered
is false for it, and an emitted death or publication mark takes the object
out of a candidate buffer only when buf is below -1. A pass that walks
such an object as a child restores the value when it survives.
The runtime call reads the cert and key options before the SNICallback,
so a cert or key initializer after the callback that reassigned the
callback's binding changed the callback the server used, and the server
could serve the wrong certificate. When SNICallback comes before a cert
or key entry, the callback is now saved just before the next of them is
evaluated. With the callback read in order, a callback expression with
side effects lowers instead of being refused.
A counted for loop needs a stable limit to run its counter in integer
storage. Array lengths qualified when the loop provably keeps them, but
a string's length did not, so `for (let i = 0; i < s.length; i++)`
kept a double counter and evaluated the length, through the UTF-16
mapping of a non-ASCII string, on every iteration. A string's length
cannot change, so it is now stable whenever the string's binding is
not rebound in the loop or boxed.
dyn.nameClassPrototype sets the class name on a class's runtime prototype
object and stores no property. The int32 field analysis did not list it as
read-only, so every program that gave a class a runtime prototype counted a
dynamic store that can name any property, and the number fields of every
class reaching dynamic code were stored as doubles.
The type mapper maps the type inferred from an empty object literal to the
empty record as an arm of an unreduced union and to a checked-dynamic
value elsewhere, but both answers shared one memo entry. Once the type had
been mapped on its own, a union such as `typeof empty | DataView` reused
the dynamic answer for its arm and refused (SC2009). The memo key now
includes whether the mapping is for such an arm.
On the error path, a callback's result reads from a checked-dynamic
slot. Passing it on into a Buffer parameter still handed over the
adapter's original value, so after `if (!out) out = Buffer.from(...)`
a typed callee received the absent Buffer instead of the fallback and
crashed. The forward now tests the slot: while it holds undefined the
callee gets the absent Buffer, and otherwise the Buffer the slot holds.
An array helper specialized for its callback calls the callback's
function directly once the closure's entry matches it, and falls back to
the entry otherwise. Both paths were followed by the pending-exception
test. When the direct target is outside the may-throw set, only the
fallback can leave an exception pending, so the test now runs behind a
guard that is true on that path alone; a known closure called directly
skips it. Worker programs keep the test on every path, where it also
observes termination.
Constructor types declared in the program hold class values as
checked-dynamic values since #1725. A fetched provenance source counts as
a program file, so the unused `@__PURE__` const typed `{ new (): any }` in
the provenance fixture now had a mapping, no longer elided, and its
initializer refused (SC1090). Fetched sources keep their constructor types
unmapped, as before #1725.
A `for` loop's initializer and a `for...of` loop's iterable run once, but
SC6101 counted any dynamic operation inside a loop statement's span, so
untyped setup there produced the warning and failed --fail-on=dynamic.
Loop work is now found by walking the IR: a loop's condition, update and
body repeat, its initializer and iterable do not. Locations could not
tell them apart, because lowering gives the index loop of a `for...of`
the whole statement's span.
The wrapper is dropped when its factory body moves to the top level, so
any other statement in the wrapper, in its CommonJS branch or in its AMD
branch would be lost. The check now matches the whole wrapper body and
keeps the original text for any other shape.
The arguments after a URL path that are evaluated ahead of the
conversion were keyed by the expression without its parentheses. When
the fs lowering read through a satisfies wrapper, it lowered the inner
expression again, so fs.chmodSync(url, mode() satisfies number) called
mode() twice. The saved arguments are now keyed and looked up without
their type-only wrappers (satisfies, as, type assertions, !), so each
runs once.
A constructor type whose instances are not one program class's, such as
`new () => unknown`, a type that also names static members (`{ readonly
schema: unknown; new (): unknown }`), an abstract constructor type over a
record, or construct overloads, did not map and refused with SC2001. Such
a type declared in the program now lowers as a checked-dynamic value, as
an `unknown` slot already holds a class value: the value keeps its class
identity, `new` through it constructs that class, static reads see that
class's statics, and the constructed value checks into the signature's
instance type. Library and package constructor types keep their fences.
Refs #1372
Co-authored-by: blurname <50226652+blurname@users.noreply.github.com>
A build now names the functions of the program's own files that compile
to the dynamic tier and likely run often, so a slow program with a little
untyped code says where the time goes:
warning SC6101: 3 functions that likely run often use untyped values, which runs slower than typed code:
advance (nbody.js:22): untyped JavaScript file, in a loop
...
- The functions come from the tier assignment lowering already makes
(Lowerer.dynamicFunctions). Without a profile, a function counts as
likely hot when a dynamic operation runs inside one of its loops, when
a loop calls it, or when it calls itself (lowering/dynamic-tier.ts).
- A function is named only when its source says why its values are
untyped: an `any` (for a for...of variable, the value it iterates), an
untyped JSON.parse result, or an untyped JavaScript file. Generated
%dyn.* helpers, module top levels and functions that are dynamic for an
operation without a static lowering are left out.
- At most five functions are named, most likely hot first, with the
total; dynamic-tier code in npm packages is counted per package on one
line. All of the warning's text is in diagnostics/dynamic-tier.ts.
- SC6101 opens the SC61xx band, performance notes, with a new
"performance" category in the diagnostics envelope; SC60xx stay the
divergences.
- scriptc build prints it after the divergence warnings, and the
executable cache stores it with the entry, so a cached build (including
the CLI's routed fast path) repeats it. scriptc coverage reports it, and
a comment-only edit no longer replays a verdict that carries it, since
its text holds line numbers.
- --no-dynamic-tier-warning leaves it out of build and coverage;
coverage --fail-on=dynamic fails on it.
- Docs: coverage.mdx (Dynamic tier, Gating builds and CI, the envelope
categories) and cli.mdx.
Chris Tate