From 4e2c3a9068e2df407e3193fe148d1492a0db5653 Mon Sep 17 00:00:00 2001
From: Eli White <github@eli-white.com>
Date: Wed, 5 Feb 2025 16:45:39 -0800
Subject: [PATCH] Only set alternate/consequent if terminal is goto

---
 .../src/HIR/Environment.ts                       |  2 +-
 .../src/Optimization/ConstantPropagation.ts      | 16 ++++++++++++++--
 .../AlignReactiveScopesToBlockScopesHIR.ts       |  2 +-
 .../constant-propagation-ternary-unary.js        |  2 +-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts b/compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts
index bfd2608739..ec50d85856 100644
--- a/compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts
+++ b/compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts
@@ -632,7 +632,7 @@ const EnvironmentConfigSchema = z.object({
    * // output
    * const x = b;
    */
-  enableTernaryConstantPropagation: z.boolean().default(false),
+  enableTernaryConstantPropagation: z.boolean().default(true),
 });
 
 export type EnvironmentConfig = z.infer<typeof EnvironmentConfigSchema>;
diff --git a/compiler/packages/babel-plugin-react-compiler/src/Optimization/ConstantPropagation.ts b/compiler/packages/babel-plugin-react-compiler/src/Optimization/ConstantPropagation.ts
index 273039643a..47bcddb0d4 100644
--- a/compiler/packages/babel-plugin-react-compiler/src/Optimization/ConstantPropagation.ts
+++ b/compiler/packages/babel-plugin-react-compiler/src/Optimization/ConstantPropagation.ts
@@ -190,8 +190,20 @@ function applyConstantPropagation(
             loc: terminal.loc,
           };
 
-          fn.body.blocks.get(branchBlock.terminal.consequent)!.kind = 'block';
-          fn.body.blocks.get(branchBlock.terminal.alternate)!.kind = 'block';
+          block.kind = 'block';
+
+          const consequent = fn.body.blocks.get(
+            branchBlock.terminal.consequent,
+          )!;
+          const alternate = fn.body.blocks.get(branchBlock.terminal.alternate)!;
+
+          if (consequent.terminal.kind === 'goto') {
+            consequent.kind = 'block';
+          }
+
+          if (alternate.terminal.kind === 'goto') {
+            alternate.kind = 'block';
+          }
         }
 
         break;
diff --git a/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/AlignReactiveScopesToBlockScopesHIR.ts b/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/AlignReactiveScopesToBlockScopesHIR.ts
index 2b4e890a40..e96ff83dd6 100644
--- a/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/AlignReactiveScopesToBlockScopesHIR.ts
+++ b/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/AlignReactiveScopesToBlockScopesHIR.ts
@@ -216,7 +216,7 @@ export function alignReactiveScopesToBlockScopesHIR(fn: HIRFunction): void {
         if (node == null) {
           // Transition from block->value block, derive the outer block range
           CompilerError.invariant(fallthrough !== null, {
-            reason: `Expected a fallthrough for value block`,
+            reason: `Expected a fallthrough for value block ${terminal.id}`,
             loc: terminal.loc,
           });
           const fallthroughBlock = fn.body.blocks.get(fallthrough)!;
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/constant-propagation-ternary-unary.js b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/constant-propagation-ternary-unary.js
index 7dda1f6960..f74185e36a 100644
--- a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/constant-propagation-ternary-unary.js
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/constant-propagation-ternary-unary.js
@@ -4,7 +4,7 @@ import {Stringify} from 'shared-runtime';
 function foo() {
   let _b;
   const b = true;
-  _b = !b ? 'bar' : 'baz';
+  _b = !b ? 'bar' : false ? 'foo' : 'baz';
 
   return (
     <Stringify