[hir-rewrite] Remove breaks to HIR ScopeTerminal after converting to reactiveFunction IR

ghstack-source-id: 67e979e1533b23ced762973e239a4290111e2242
Pull Request resolved: https://github.com/facebook/react-forget/pull/2911

compiler/packages/babel-plugin-react-forget/src/Entrypoint/Pipeline.ts

@@ -46,6 +46,7 @@ import {
   alignObjectMethodScopes,
   alignReactiveScopesToBlockScopes,
   assertScopeInstructionsWithinScopes,
+  assertWellFormedBreakTargets,
   buildReactiveBlocks,
   buildReactiveFunction,
   codegenFunction,
@@ -279,6 +280,8 @@ function* runWithEnvironment(
     value: reactiveFunction,
   });
 
+  assertWellFormedBreakTargets(reactiveFunction);
+
   pruneUnusedLabels(reactiveFunction);
   yield log({
     kind: "reactive",

compiler/packages/babel-plugin-react-forget/src/ReactiveScopes/AssertWellFormedBreakTargets.ts

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import { CompilerError } from "..";
+import { BlockId, ReactiveFunction, ReactiveTerminalStatement } from "../HIR";
+import { ReactiveFunctionVisitor, visitReactiveFunction } from "./visitors";
+
+/**
+ * Assert that all break/continue targets reference existent labels.
+ */
+export function assertWellFormedBreakTargets(fn: ReactiveFunction): void {
+  visitReactiveFunction(fn, new Visitor(), new Set());
+}
+
+class Visitor extends ReactiveFunctionVisitor<Set<BlockId>> {
+  override visitTerminal(
+    stmt: ReactiveTerminalStatement,
+    seenLabels: Set<BlockId>
+  ): void {
+    if (stmt.label != null) {
+      seenLabels.add(stmt.label.id);
+    }
+    const terminal = stmt.terminal;
+    if (terminal.kind === "break" || terminal.kind === "continue") {
+      CompilerError.invariant(seenLabels.has(terminal.target), {
+        reason: "Unexpected break to invalid label",
+        loc: stmt.terminal.loc,
+      });
+    }
+  }
+}

compiler/packages/babel-plugin-react-forget/src/ReactiveScopes/BuildReactiveFunction.ts

@@ -813,6 +813,7 @@ class Driver {
         if (fallthroughId !== null) {
           const scheduleId = this.cx.schedule(fallthroughId, "if");
           scheduleIds.push(scheduleId);
+          this.cx.scopeFallthroughs.add(fallthroughId);
         }
 
         let block: ReactiveBlock;
@@ -1169,7 +1170,7 @@ class Driver {
     block: BlockId,
     id: InstructionId,
     loc: SourceLocation
-  ): ReactiveTerminalStatement<ReactiveBreakTerminal> {
+  ): ReactiveTerminalStatement<ReactiveBreakTerminal> | null {
     const target = this.cx.getBreakTarget(block);
     if (target === null) {
       CompilerError.invariant(false, {
@@ -1179,6 +1180,13 @@ class Driver {
         suggestions: null,
       });
     }
+    if (this.cx.scopeFallthroughs.has(target.block)) {
+      CompilerError.invariant(target.type === "implicit", {
+        reason: "Expected reactive scope to implicitly break to fallthrough",
+        loc,
+      });
+      return null;
+    }
     return {
       kind: "terminal",
       terminal: {
@@ -1231,6 +1239,7 @@ class Context {
    */
   emitted: Set<BlockId> = new Set();
 
+  scopeFallthroughs: Set<BlockId> = new Set();
   /*
    * A set of blocks that are already scheduled to be emitted by eg a parent.
    * This allows child nodes to avoid re-emitting the same block and emit eg
@@ -1361,9 +1370,10 @@ class Context {
    *
    * The returned 'block' value should be used as the label if necessary.
    */
-  getBreakTarget(
-    block: BlockId
-  ): { block: BlockId; type: ReactiveTerminalTargetKind } | null {
+  getBreakTarget(block: BlockId): {
+    block: BlockId;
+    type: ReactiveTerminalTargetKind;
+  } {
     let hasPrecedingLoop = false;
     for (let i = this.#controlFlowStack.length - 1; i >= 0; i--) {
       const target = this.#controlFlowStack[i]!;
@@ -1392,7 +1402,13 @@ class Context {
       }
       hasPrecedingLoop ||= target.type === "loop";
     }
-    return null;
+
+    CompilerError.invariant(false, {
+      reason: "Expected a break target",
+      description: null,
+      loc: null,
+      suggestions: null,
+    });
   }
 
   /*

compiler/packages/babel-plugin-react-forget/src/ReactiveScopes/index.ts

@@ -8,6 +8,7 @@
 export { alignObjectMethodScopes } from "./AlignObjectMethodScopes";
 export { alignReactiveScopesToBlockScopes } from "./AlignReactiveScopesToBlockScopes";
 export { assertScopeInstructionsWithinScopes } from "./AssertScopeInstructionsWithinScope";
+export { assertWellFormedBreakTargets } from "./AssertWellFormedBreakTargets";
 export { buildReactiveBlocks } from "./BuildReactiveBlocks";
 export { buildReactiveFunction } from "./BuildReactiveFunction";
 export {