inferReactiveScopeVariables() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/InferReactiveScopeVariables.ts lines 86–172

export function inferReactiveScopeVariables(fn: HIRFunction): void {
  /*
   * Represents the set of reactive scopes as disjoint sets of identifiers
   * that mutate together.
   */
  const scopeIdentifiers = findDisjointMutableValues(fn);

  // Maps each scope (by its identifying member) to a ScopeId value
  const scopes: Map<Identifier, ReactiveScope> = new Map();

  /*
   * Iterate over all the identifiers and assign a unique ScopeId
   * for each scope (based on the set identifier).
   *
   * At the same time, group the identifiers in each scope and
   * build a MutableRange that describes the span of mutations
   * across all identifiers in each scope.
   */
  scopeIdentifiers.forEach((identifier, groupIdentifier) => {
    let scope = scopes.get(groupIdentifier);
    if (scope === undefined) {
      scope = {
        id: fn.env.nextScopeId,
        range: identifier.mutableRange,
        dependencies: new Set(),
        declarations: new Map(),
        reassignments: new Set(),
        earlyReturnValue: null,
        merged: new Set(),
        loc: identifier.loc,
      };
      scopes.set(groupIdentifier, scope);
    } else {
      if (scope.range.start === 0) {
        scope.range.start = identifier.mutableRange.start;
      } else if (identifier.mutableRange.start !== 0) {
        scope.range.start = makeInstructionId(
          Math.min(scope.range.start, identifier.mutableRange.start),
        );
      }
      scope.range.end = makeInstructionId(
        Math.max(scope.range.end, identifier.mutableRange.end),
      );
      scope.loc = mergeLocation(scope.loc, identifier.loc);
    }
    identifier.scope = scope;
    identifier.mutableRange = scope.range;
  });

  let maxInstruction = 0;
  for (const [, block] of fn.body.blocks) {
    for (const instr of block.instructions) {
      maxInstruction = makeInstructionId(Math.max(maxInstruction, instr.id));
    }
    maxInstruction = makeInstructionId(
      Math.max(maxInstruction, block.terminal.id),
    );
  }

  /*
   * Validate that all scopes have properly intialized, valid mutable ranges
   * within the span of instructions for this function, ie from 1 to 1 past
   * the last instruction id.
   */
  for (const [, scope] of scopes) {
    if (
      scope.range.start === 0 ||
      scope.range.end === 0 ||
      maxInstruction === 0 ||
      scope.range.end > maxInstruction + 1
    ) {
      // Make it easier to debug why the error occurred
      fn.env.logger?.debugLogIRs?.({
        kind: 'hir',
        name: 'InferReactiveScopeVariables (invalid scope)',
        value: fn,
      });
      CompilerError.invariant(false, {
        reason: `Invalid mutable range for scope`,
        description: `Scope @${scope.id} has range [${scope.range.start}:${
          scope.range.end