isImmutableAtInstr() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/HIR/CollectHoistablePropertyLoads.ts lines 344–378

function isImmutableAtInstr(
  identifier: Identifier,
  instr: InstructionId,
  context: CollectHoistablePropertyLoadsContext,
): boolean {
  if (context.nestedFnImmutableContext != null) {
    /**
     * Comparing instructions ids across inner-outer function bodies is not valid, as they are numbered
     */
    return context.nestedFnImmutableContext.has(identifier.id);
  } else {
    /**
     * Since this runs *after* buildReactiveScopeTerminals, identifier mutable ranges
     * are not valid with respect to current instruction id numbering.
     * We use attached reactive scope ranges as a proxy for mutable range, but this
     * is an overestimate as (1) scope ranges merge and align to form valid program
     * blocks and (2) passes like MemoizeFbtAndMacroOperands may assign scopes to
     * non-mutable identifiers.
     *
     * See comment in exported function for why we track known immutable identifiers.
     */
    const mutableAtInstr =
      identifier.mutableRange.end > identifier.mutableRange.start + 1 &&
      identifier.scope != null &&
      inRange(
        {
          id: instr,
        },
        identifier.scope.range,
      );
    return (
      !mutableAtInstr || context.knownImmutableIdentifiers.has(identifier.id)
    );
  }
}