Add annotations to fix future errors after fix for unsound array types

Summary:
X-link: react/react-native#52691

Unannotated array literals are unsound in Flow right now. This diff adds in annotations and makes a few things readonly, to reduce future errors.

Changelog: [Internal]

Reviewed By: marcoww6

Differential Revision: D78519638

fbshipit-source-id: d98a7668ecf97bcc87dcb3fad25ade736d885d9a

Author: SamChou19815

packages/metro-source-map/src/__tests__/composeSourceMaps-test.js

@@ -137,7 +137,7 @@ describe('composeSourceMaps', () => {
   });
 
   test('preserves x_facebook_sources', () => {
-    const map1 = {
+    const map1: MixedSourceMap = {
       version: 3,
       sections: [
         {
@@ -153,7 +153,7 @@ describe('composeSourceMaps', () => {
       ],
     };
 
-    const map2 = {
+    const map2: MixedSourceMap = {
       version: 3,
       sources: ['src-transformed.js'],
       names: ['gLoBAl'],
@@ -168,7 +168,7 @@ describe('composeSourceMaps', () => {
   });
 
   test('preserves and reindexes x_google_ignoreList', () => {
-    const map1 = {
+    const map1: MixedSourceMap = {
       version: 3,
       sections: [
         {
@@ -184,7 +184,7 @@ describe('composeSourceMaps', () => {
       ],
     };
 
-    const map2 = {
+    const map2: MixedSourceMap = {
       version: 3,
       sources: ['src-transformed.js'],
       names: ['gLoBAl'],
@@ -202,7 +202,7 @@ describe('composeSourceMaps', () => {
   });
 
   test('x_google_ignoreList: a source with inconsistent ignore status is considered to be ignored', () => {
-    const map1 = {
+    const map1: MixedSourceMap = {
       version: 3,
       sections: [
         {
@@ -234,7 +234,7 @@ describe('composeSourceMaps', () => {
       ],
     };
 
-    const map2 = {
+    const map2: MixedSourceMap = {
       version: 3,
       sources: ['src-transformed.js'],
       names: ['gLoBAl'],
@@ -255,7 +255,7 @@ describe('composeSourceMaps', () => {
   });
 
   test('preserves sourcesContent', () => {
-    const map1 = {
+    const map1: MixedSourceMap = {
       version: 3,
       sections: [
         {
@@ -272,7 +272,7 @@ describe('composeSourceMaps', () => {
       ],
     };
 
-    const map2 = {
+    const map2: MixedSourceMap = {
       version: 3,
       sources: ['transformed.js'],
       names: ([]: Array<string>),

packages/metro-source-map/src/__tests__/generateFunctionMap-test.js

@@ -12,6 +12,7 @@
 'use strict';
 
 import type {Context} from '../generateFunctionMap';
+import type {MixedSourceMap} from '../source-map';
 import type {NodePath} from '@babel/traverse';
 import type {MetroBabelFileMetadata} from 'metro-babel-transformer';
 
@@ -1435,7 +1436,7 @@ function parent2() {
     const mappings = generateFunctionMappingsArray(ast);
     const encoded = generateFunctionMap(ast);
 
-    const sourceMap = {
+    const sourceMap: MixedSourceMap = {
       version: 3,
       sources: ['input.js'],
       names: ([]: Array<string>),