[compiler] Add Identifier.declarationId

Adds `Identifier.declarationId` and the new `DeclarationId` (simulated) opaque type. DeclarationId allows uniquely identifying a variable in the original source, ie regardless of reassignments. This allows us to stay in SSA form throughout compilation (see next diff) while still being able to distinguish SSA versions (via IdentifierId) and non-SSA versions (DeclarationId).

ghstack-source-id: f2547a58aa7b30cea29fcfe23d5cb45583858a4e
Pull Request resolved: #30569

compiler/packages/babel-plugin-react-compiler/src/HIR/HIR.ts

@@ -1174,11 +1174,19 @@ export type NonLocalBinding =
 
 // Represents a user-defined variable (has a name) or a temporary variable (no name).
 export type Identifier = {
-  /*
-   * unique value to distinguish a variable, since name is not guaranteed to
-   * exist or be unique
+  /**
+   * After EnterSSA, `id` uniquely identifies an SSA instance of a variable.
+   * Before EnterSSA, `id` matches `declarationId`.
    */
   id: IdentifierId;
+
+  /**
+   * Uniquely identifies a given variable in the original program. If a value is
+   * reassigned in the original program each reassigned value will have a distinct
+   * `id` (after EnterSSA), but they will still have the same `declarationId`.
+   */
+  declarationId: DeclarationId;
+
   // null for temporaries. name is primarily used for debugging.
   name: IdentifierName | null;
   // The range for which this variable is mutable
@@ -1212,6 +1220,7 @@ export function makeTemporaryIdentifier(
   return {
     id,
     name: null,
+    declarationId: makeDeclarationId(id),
     mutableRange: {start: makeInstructionId(0), end: makeInstructionId(0)},
     scope: null,
     type: makeType(),
@@ -1508,6 +1517,23 @@ export function makeIdentifierId(id: number): IdentifierId {
   return id as IdentifierId;
 }
 
+/*
+ * Simulated opaque type for IdentifierId to prevent using normal numbers as ids
+ * accidentally.
+ */
+const opageDeclarationId = Symbol();
+export type DeclarationId = number & {[opageDeclarationId]: 'DeclarationId'};
+
+export function makeDeclarationId(id: number): DeclarationId {
+  CompilerError.invariant(id >= 0 && Number.isInteger(id), {
+    reason: 'Expected declaration id to be a non-negative integer',
+    description: null,
+    loc: null,
+    suggestions: null,
+  });
+  return id as DeclarationId;
+}
+
 /*
  * Simulated opaque type for InstructionId to prevent using normal numbers as ids
  * accidentally.

compiler/packages/babel-plugin-react-compiler/src/HIR/HIRBuilder.ts

@@ -25,6 +25,7 @@ import {
   Terminal,
   VariableBinding,
   makeBlockId,
+  makeDeclarationId,
   makeIdentifierName,
   makeInstructionId,
   makeTemporaryIdentifier,
@@ -320,6 +321,7 @@ export default class HIRBuilder {
         const id = this.nextIdentifierId;
         const identifier: Identifier = {
           id,
+          declarationId: makeDeclarationId(id),
           name: makeIdentifierName(name),
           mutableRange: {
             start: makeInstructionId(0),

compiler/packages/babel-plugin-react-compiler/src/Inference/InlineImmediatelyInvokedFunctionExpressions.ts

@@ -8,7 +8,6 @@
 import {
   BasicBlock,
   BlockId,
-  Effect,
   Environment,
   FunctionExpression,
   GeneratedSource,
@@ -19,11 +18,14 @@ import {
   LabelTerminal,
   Place,
   makeInstructionId,
-  makeType,
   promoteTemporary,
   reversePostorderBlocks,
 } from '../HIR';
-import {markInstructionIds, markPredecessors} from '../HIR/HIRBuilder';
+import {
+  createTemporaryPlace,
+  markInstructionIds,
+  markPredecessors,
+} from '../HIR/HIRBuilder';
 import {eachInstructionValueOperand} from '../HIR/visitors';
 import {retainWhere} from '../Utils/utils';
 
@@ -225,23 +227,7 @@ function rewriteBlock(
   block.instructions.push({
     id: makeInstructionId(0),
     loc: terminal.loc,
-    lvalue: {
-      effect: Effect.Unknown,
-      identifier: {
-        id: env.nextIdentifierId,
-        mutableRange: {
-          start: makeInstructionId(0),
-          end: makeInstructionId(0),
-        },
-        name: null,
-        scope: null,
-        type: makeType(),
-        loc: terminal.loc,
-      },
-      kind: 'Identifier',
-      reactive: false,
-      loc: terminal.loc,
-    },
+    lvalue: createTemporaryPlace(env, terminal.loc),
     value: {
       kind: 'StoreLocal',
       lvalue: {kind: InstructionKind.Reassign, place: {...returnValue}},
@@ -267,23 +253,7 @@ function declareTemporary(
   block.instructions.push({
     id: makeInstructionId(0),
     loc: GeneratedSource,
-    lvalue: {
-      effect: Effect.Unknown,
-      identifier: {
-        id: env.nextIdentifierId,
-        mutableRange: {
-          start: makeInstructionId(0),
-          end: makeInstructionId(0),
-        },
-        name: null,
-        scope: null,
-        type: makeType(),
-        loc: result.loc,
-      },
-      kind: 'Identifier',
-      reactive: false,
-      loc: GeneratedSource,
-    },
+    lvalue: createTemporaryPlace(env, result.loc),
     value: {
       kind: 'DeclareLocal',
       lvalue: {

compiler/packages/babel-plugin-react-compiler/src/SSA/EnterSSA.ts

@@ -79,6 +79,7 @@ class SSABuilder {
   makeId(oldId: Identifier): Identifier {
     return {
       id: this.nextSsaId,
+      declarationId: oldId.declarationId,
       name: oldId.name,
       mutableRange: {
         start: makeInstructionId(0),