areArgumentsImmutableAndNonMutating() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/Inference/InferMutationAliasingEffects.ts lines 2506–2561

function areArgumentsImmutableAndNonMutating(
  state: InferenceState,
  args: Array<Place | SpreadPattern | Hole>,
): boolean {
  for (const arg of args) {
    if (arg.kind === 'Hole') {
      continue;
    }
    if (arg.kind === 'Identifier' && arg.identifier.type.kind === 'Function') {
      const fnShape = state.env.getFunctionSignature(arg.identifier.type);
      if (fnShape != null) {
        return (
          !fnShape.positionalParams.some(isKnownMutableEffect) &&
          (fnShape.restParam == null ||
            !isKnownMutableEffect(fnShape.restParam))
        );
      }
    }
    const place = arg.kind === 'Identifier' ? arg : arg.place;

    const kind = state.kind(place).kind;
    switch (kind) {
      case ValueKind.Primitive:
      case ValueKind.Frozen: {
        /*
         * Only immutable values, or frozen lambdas are allowed.
         * A lambda may appear frozen even if it may mutate its inputs,
         * so we have a second check even for frozen value types
         */
        break;
      }
      default: {
        /**
         * Globals, module locals, and other locally defined functions may
         * mutate their arguments.
         */
        return false;
      }
    }
    const values = state.values(place);
    for (const value of values) {
      if (
        value.kind === 'FunctionExpression' &&
        value.loweredFunc.func.params.some(param => {
          const place = param.kind === 'Identifier' ? param : param.place;
          const range = place.identifier.mutableRange;
          return range.end > range.start + 1;
        })
      ) {
        // This is a function which may mutate its inputs
        return false;
      }
    }
  }
  return true;
}