With the shape overlay on, a first round of structural rewrites runs before
the typed overlay (shape-inference/static-objects.ts, stage 2b of
DESIGN-constant-objects.md), proven by the constant object graphs:
- An ES5 constructor stored by a top-level statement whose prototype is a
constant object of plain methods becomes a class declaration with those
methods, when the program cannot tell: the function is only ever
constructed and never escapes, its prototype is never replaced, nothing
enumerates instances with for-in or reflects on the prototype or the
function, nothing reads their names or sources, the bodies are
strict-mode safe, and only definitions run between the constructor and
its last method.
- A constant namespace member holding a `this`-free function expression
becomes a function declaration, and reads of the member in the same file
whose receiver is exactly that constant object refer to it directly.
The rounds rerun the analysis on the rebuilt program, the overlay now also
covers the program's own JavaScript files, and the build report counts the
rewrites. A JavaScript switch whose case tests lower to another type than
the discriminant compares with === instead of being refused.
Namespace benchmark (n=20000): 1.55 s -> 0.42-0.47 s, output identical to
Node (typed TypeScript twin 85 ms, Node 21 ms).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Chris Tate