Fix for invalid mutable range in phi with backedge

Fixes the repro added in 947832009997bf9149e88e583c46cc39f6a6136c - previously 
when computing mutable ranges of phis, we didn't check that all operands had 
been visited. This meant that a backedge could allow a phi's mutable range to 
start at 0. Then in PropagateScopeDeps, we might see reject dependencies of a 
scope since they appeared to start after a scope — only because the scope's 
start was incorrectly too early. 

The fix here is to initially set phi.id mutable ranges based on only on operands 
that are already visited. Then, during/after the fixpoint iteration of 
InferMutableRanges, we start account for all operands since we know they've been 
visited at least once and have a real range.

compiler/packages/babel-plugin-react-forget/src/Inference/InferMutableLifetimes.ts

@@ -5,7 +5,6 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import { CompilerError } from "../CompilerError";
 import {
   Effect,
   HIRFunction,
@@ -102,22 +101,30 @@ export function inferMutableLifetimes(
 ): void {
   for (const [_, block] of func.body.blocks) {
     for (const phi of block.phis) {
-      let start = Number.MAX_SAFE_INTEGER;
-      let end = phi.id.mutableRange.end as number;
       for (const [_, operand] of phi.operands) {
-        start = Math.min(start, operand.mutableRange.start);
-        end = Math.max(end, operand.mutableRange.end);
+        if (
+          operand.mutableRange.start === 0 &&
+          operand.mutableRange.end === 0
+        ) {
+          // operand's range is uninitialized, skip
+          continue;
+        } else if (
+          phi.id.mutableRange.start === 0 &&
+          phi.id.mutableRange.end === 0
+        ) {
+          // phi's range is uninitialized, take the range from the operand
+          phi.id.mutableRange.start = operand.mutableRange.start;
+          phi.id.mutableRange.end = operand.mutableRange.end;
+        } else {
+          // else join the phi and operand's range
+          phi.id.mutableRange.start = makeInstructionId(
+            Math.min(phi.id.mutableRange.start, operand.mutableRange.start)
+          );
+          phi.id.mutableRange.end = makeInstructionId(
+            Math.max(phi.id.mutableRange.end, operand.mutableRange.end)
+          );
+        }
       }
-      CompilerError.invariant(start !== Number.MAX_SAFE_INTEGER, {
-        reason: "Expected phi to have a start range value",
-        description: null,
-        loc: null,
-        suggestions: null,
-      });
-      phi.id.mutableRange = {
-        start: makeInstructionId(start),
-        end: makeInstructionId(end),
-      };
     }
 
     for (const instr of block.instructions) {

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/bug-repro-missing-dependency-if-within-while.expect.md

@@ -39,11 +39,11 @@ export const FIXTURE_ENTRYPOINT = {
 import { unstable_useMemoCache as useMemoCache } from "react";
 const someGlobal = true;
 export default function Component(props) {
-  const $ = useMemoCache(1);
+  const $ = useMemoCache(4);
   const { b } = props;
-  let t0;
-  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
-    const items = [];
+  let items;
+  if ($[0] !== b) {
+    items = [];
     let i = 0;
     while (i < 10) {
       if (someGlobal) {
@@ -51,11 +51,18 @@ export default function Component(props) {
         i++;
       }
     }
-
-    t0 = <>{items}</>;
-    $[0] = t0;
+    $[0] = b;
+    $[1] = items;
   } else {
-    t0 = $[0];
+    items = $[1];
+  }
+  let t0;
+  if ($[2] !== items) {
+    t0 = <>{items}</>;
+    $[2] = items;
+    $[3] = t0;
+  } else {
+    t0 = $[3];
   }
   return t0;
 }
@@ -76,4 +83,13 @@ export const FIXTURE_ENTRYPOINT = {
 };
 
 ```
-      
+      
+### Eval output
+(kind: ok) <div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div>
+<div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div>
+<div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div>
+<div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div>
+<div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div>
+<div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div>
+<div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div><div>0</div>
+<div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div><div>42</div>

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/for-in-statement-continue.expect.md

@@ -16,7 +16,17 @@ function Component(props) {
 
 export const FIXTURE_ENTRYPOINT = {
   fn: Component,
-  params: [{ value: { a: "a", continue: "skip", b: "b!" } }],
+  params: [{ value: { a: "a", continue: "skip", b: "hello!" } }],
+  sequentialRenders: [
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "skip!", continue: true } },
+  ],
 };
 
 ```
@@ -26,18 +36,10 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { unstable_useMemoCache as useMemoCache } from "react";
 function Component(props) {
-  const $ = useMemoCache(3);
+  const $ = useMemoCache(2);
   let x;
-  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
-    let t0;
-    if ($[1] !== props.value) {
-      t0 = { ...props.value };
-      $[1] = props.value;
-      $[2] = t0;
-    } else {
-      t0 = $[2];
-    }
-    const object = t0;
+  if ($[0] !== props.value) {
+    const object = { ...props.value };
     for (const y in object) {
       if (y === "continue") {
         continue;
@@ -45,19 +47,37 @@ function Component(props) {
 
       x = object[y];
     }
-    $[0] = x;
+    $[0] = props.value;
+    $[1] = x;
   } else {
-    x = $[0];
+    x = $[1];
   }
   return x;
 }
 
 export const FIXTURE_ENTRYPOINT = {
   fn: Component,
-  params: [{ value: { a: "a", continue: "skip", b: "b!" } }],
+  params: [{ value: { a: "a", continue: "skip", b: "hello!" } }],
+  sequentialRenders: [
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "skip!", continue: true } },
+  ],
 };
 
 ```
       
 ### Eval output
-(kind: ok) "b!"
+(kind: ok) "hello!"
+"hello!"
+"skip!"
+"hello!"
+"skip!"
+"hello!"
+"skip!"
+"skip!"

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/for-in-statement-continue.js

@@ -12,5 +12,15 @@ function Component(props) {
 
 export const FIXTURE_ENTRYPOINT = {
   fn: Component,
-  params: [{ value: { a: "a", continue: "skip", b: "b!" } }],
+  params: [{ value: { a: "a", continue: "skip", b: "hello!" } }],
+  sequentialRenders: [
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "a", continue: "skip", b: "hello!" } },
+    { value: { a: "skip!", continue: true } },
+    { value: { a: "skip!", continue: true } },
+  ],
 };

compiler/packages/snap/src/SproutTodoFilter.ts

@@ -534,7 +534,6 @@ const skipFilter = new Set([
   // bugs
   "bug-reduce-reactive-deps-return-in-scope",
   "bug-reduce-reactive-deps-break-in-scope",
-  "bug-repro-missing-dependency-if-within-while",
 
   // 'react-forget-runtime' not yet supported
   "flag-enable-emit-hook-guards",