compiler: Use types to decide which scopes are eligible for merging

In MergeReactiveScopesThatInvalidateTogether when deciding which scopes were eligible for mergin at all, we looked specifically at the instructions whose lvalue produces the declaration. So if a scope declaration was `t0`, we'd love for the instruction where `t0` was the lvalue and look at the instruction type to decide if it is eligible for merging.

Here, we use the inferred type instead (now that the inferred types support the same set of types of instructions we looked at before). This allows us to find more cases where scopes can be merged.

ghstack-source-id: 22e49606056cd37220892cc2298b1318147b97da
Pull Request resolved: #29157

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/MergeReactiveScopesThatInvalidateTogether.ts

@@ -13,7 +13,6 @@ import {
   Place,
   ReactiveBlock,
   ReactiveFunction,
-  ReactiveInstruction,
   ReactiveScope,
   ReactiveScopeBlock,
   ReactiveScopeDependencies,
@@ -514,64 +513,7 @@ function scopeIsEligibleForMerging(scopeBlock: ReactiveScopeBlock): boolean {
      */
     return true;
   }
-  const visitor = new DeclarationTypeVisitor(scopeBlock.scope);
-  visitor.visitScope(scopeBlock, undefined);
-  return visitor.alwaysInvalidatesOnInputChange;
-}
-
-class DeclarationTypeVisitor extends ReactiveFunctionVisitor<void> {
-  scope: ReactiveScope;
-  alwaysInvalidatesOnInputChange: boolean = false;
-
-  constructor(scope: ReactiveScope) {
-    super();
-    this.scope = scope;
-  }
-
-  override visitScope(scopeBlock: ReactiveScopeBlock, state: void): void {
-    if (scopeBlock.scope.id !== this.scope.id) {
-      return;
-    }
-    this.traverseScope(scopeBlock, state);
-  }
-
-  override visitInstruction(
-    instruction: ReactiveInstruction,
-    state: void
-  ): void {
-    this.traverseInstruction(instruction, state);
-    if (
-      instruction.lvalue === null ||
-      !this.scope.declarations.has(instruction.lvalue.identifier.id)
-    ) {
-      /*
-       * no lvalue or this instruction isn't directly constructing a
-       * scope output value, skip
-       */
-      log(
-        `    skip instruction lvalue=${
-          instruction.lvalue?.identifier.id
-        } declaration?=${
-          instruction.lvalue != null &&
-          this.scope.declarations.has(instruction.lvalue.identifier.id)
-        } scope=${printReactiveScopeSummary(this.scope)}`
-      );
-      return;
-    }
-    switch (instruction.value.kind) {
-      case "FunctionExpression":
-      case "ArrayExpression":
-      case "JsxExpression":
-      case "JsxFragment":
-      case "ObjectExpression": {
-        /*
-         * These instruction types *always* allocate. If they execute
-         * they will produce a new value, triggering downstream reactive
-         * updates
-         */
-        this.alwaysInvalidatesOnInputChange = true;
-        break;
-      }
-    }
-  }
+  return [...scopeBlock.scope.declarations].some(([, decl]) =>
+    isAlwaysInvalidatingType(decl.identifier.type)
+  );
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/allocating-primitive-as-dep-nested-scope.expect.md

@@ -24,39 +24,28 @@ import { c as _c } from "react/compiler-runtime"; // bar(props.b) is an allocati
 // Correctness:
 //   - y depends on either bar(props.b) or bar(props.b) + 1
 function AllocatingPrimitiveAsDepNested(props) {
-  const $ = _c(9);
-  let x;
-  let y;
+  const $ = _c(5);
+  let t0;
   if ($[0] !== props.b || $[1] !== props.a) {
-    x = {};
+    const x = {};
     mutate(x);
-    const t0 = bar(props.b) + 1;
-    let t1;
-    if ($[4] !== t0) {
-      t1 = foo(t0);
-      $[4] = t0;
-      $[5] = t1;
+    const t1 = bar(props.b) + 1;
+    let t2;
+    if ($[3] !== t1) {
+      t2 = foo(t1);
+      $[3] = t1;
+      $[4] = t2;
     } else {
-      t1 = $[5];
+      t2 = $[4];
     }
-    y = t1;
+    const y = t2;
     mutate(x, props.a);
+    t0 = [x, y];
     $[0] = props.b;
     $[1] = props.a;
-    $[2] = x;
-    $[3] = y;
-  } else {
-    x = $[2];
-    y = $[3];
-  }
-  let t0;
-  if ($[6] !== x || $[7] !== y) {
-    t0 = [x, y];
-    $[6] = x;
-    $[7] = y;
-    $[8] = t0;
+    $[2] = t0;
   } else {
-    t0 = $[8];
+    t0 = $[2];
   }
   return t0;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/array-access-assignment.expect.md

@@ -24,40 +24,29 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function foo(a, b, c) {
-  const $ = _c(10);
-  let x;
-  let z;
+  const $ = _c(6);
+  let t0;
   if ($[0] !== a || $[1] !== b || $[2] !== c) {
-    x = [a];
-    let t0;
-    if ($[5] !== b) {
-      t0 = [null, b];
-      $[5] = b;
-      $[6] = t0;
+    const x = [a];
+    let t1;
+    if ($[4] !== b) {
+      t1 = [null, b];
+      $[4] = b;
+      $[5] = t1;
     } else {
-      t0 = $[6];
+      t1 = $[5];
     }
-    const y = t0;
-    z = [[], [], [c]];
+    const y = t1;
+    const z = [[], [], [c]];
     x[0] = y[1];
     z[0][0] = x[0];
+    t0 = [x, z];
     $[0] = a;
     $[1] = b;
     $[2] = c;
-    $[3] = x;
-    $[4] = z;
-  } else {
-    x = $[3];
-    z = $[4];
-  }
-  let t0;
-  if ($[7] !== x || $[8] !== z) {
-    t0 = [x, z];
-    $[7] = x;
-    $[8] = z;
-    $[9] = t0;
+    $[3] = t0;
   } else {
-    t0 = $[9];
+    t0 = $[3];
   }
   return t0;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/codegen-emit-make-read-only.expect.md

@@ -23,26 +23,20 @@ import { makeReadOnly } from "react-compiler-runtime";
 import { c as _c } from "react/compiler-runtime"; // @enableEmitFreeze true
 
 function MyComponentName(props) {
-  const $ = _c(5);
-  let x;
+  const $ = _c(3);
+  let y;
   if ($[0] !== props.a || $[1] !== props.b) {
-    x = {};
+    const x = {};
     foo(x, props.a);
     foo(x, props.b);
-    $[0] = props.a;
-    $[1] = props.b;
-    $[2] = __DEV__ ? makeReadOnly(x, "MyComponentName") : x;
-  } else {
-    x = $[2];
-  }
-  let y;
-  if ($[3] !== x) {
+
     y = [];
     y.push(x);
-    $[3] = x;
-    $[4] = __DEV__ ? makeReadOnly(y, "MyComponentName") : y;
+    $[0] = props.a;
+    $[1] = props.b;
+    $[2] = __DEV__ ? makeReadOnly(y, "MyComponentName") : y;
   } else {
-    y = $[4];
+    y = $[2];
   }
   return y;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/dependencies-outputs.expect.md

@@ -30,30 +30,23 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function foo(a, b) {
-  const $ = _c(5);
-  let x;
+  const $ = _c(2);
+  let y;
   if ($[0] !== a) {
-    x = [];
+    const x = [];
     x.push(a);
-    $[0] = a;
-    $[1] = x;
-  } else {
-    x = $[1];
-  }
-  let y;
-  if ($[2] !== x || $[3] !== b) {
+
     y = [];
     if (x.length) {
       y.push(x);
     }
     if (b) {
       y.push(b);
     }
-    $[2] = x;
-    $[3] = b;
-    $[4] = y;
+    $[0] = a;
+    $[1] = y;
   } else {
-    y = $[4];
+    y = $[1];
   }
   return y;
 }

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

@@ -22,25 +22,19 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function Component(props) {
-  const $ = _c(4);
-  let items;
+  const $ = _c(2);
+  let t0;
   if ($[0] !== props) {
-    items = [];
+    const items = [];
     for (const key in props) {
       items.push(<div key={key}>{key}</div>);
     }
-    $[0] = props;
-    $[1] = items;
-  } else {
-    items = $[1];
-  }
-  let t0;
-  if ($[2] !== items) {
+
     t0 = <div>{items}</div>;
-    $[2] = items;
-    $[3] = t0;
+    $[0] = props;
+    $[1] = t0;
   } else {
-    t0 = $[3];
+    t0 = $[1];
   }
   return t0;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/for-loop-with-value-block-initializer.expect.md

@@ -33,27 +33,21 @@ export const FIXTURE_ENTRYPOINT = {
 import { c as _c } from "react/compiler-runtime";
 const TOTAL = 10;
 function Component(props) {
-  const $ = _c(5);
-  let items;
+  const $ = _c(3);
+  let t0;
   if ($[0] !== props.start || $[1] !== props.items) {
-    items = [];
+    const items = [];
     for (let i = props.start ?? 0; i < props.items.length; i++) {
       const item = props.items[i];
       items.push(<div key={item.id}>{item.value}</div>);
     }
+
+    t0 = <div>{items}</div>;
     $[0] = props.start;
     $[1] = props.items;
-    $[2] = items;
-  } else {
-    items = $[2];
-  }
-  let t0;
-  if ($[3] !== items) {
-    t0 = <div>{items}</div>;
-    $[3] = items;
-    $[4] = t0;
+    $[2] = t0;
   } else {
-    t0 = $[4];
+    t0 = $[2];
   }
   return t0;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/phi-type-inference-array-push.expect.md

@@ -31,33 +31,24 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function Component(props) {
-  const $ = _c(6);
-  let x;
-  let y;
+  const $ = _c(2);
+  let t0;
   if ($[0] !== props) {
-    x = {};
+    const x = {};
+    let y;
     if (props.cond) {
       y = [props.value];
     } else {
       y = [];
     }
 
     y.push(x);
-    $[0] = props;
-    $[1] = x;
-    $[2] = y;
-  } else {
-    x = $[1];
-    y = $[2];
-  }
-  let t0;
-  if ($[3] !== x || $[4] !== y) {
+
     t0 = [x, y];
-    $[3] = x;
-    $[4] = y;
-    $[5] = t0;
+    $[0] = props;
+    $[1] = t0;
   } else {
-    t0 = $[5];
+    t0 = $[1];
   }
   return t0;
 }