Use JS arrow functions in postamble_minimal.js. NFC (#19494)

This leads to a little codesize win in all outputs!

Author: sbc100

emscripten.py

@@ -796,9 +796,9 @@ def create_receiving(exports):
       # In Wasm exports are assigned inside a function to variables
       # existing in top level JS scope, i.e.
       # var _main;
-      # WebAssembly.instantiate(Module["wasm"], imports).then((function(output) {
-      # var asm = output.instance.exports;
-      # _main = asm["_main"];
+      # WebAssembly.instantiate(Module["wasm"], imports).then((output) => {
+      #   var asm = output.instance.exports;
+      #   _main = asm["_main"];
       generate_dyncall_assignment = settings.DYNCALLS and '$dynCall' in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE
       exports_that_are_not_initializers = [x for x in exports if x != building.WASM_CALL_CTORS]
 

src/postamble_minimal.js

@@ -125,9 +125,9 @@ if (!WebAssembly.instantiateStreaming && !Module['wasm']) throw 'Must load WebAs
 #endif
 (WebAssembly.instantiateStreaming
   ? WebAssembly.instantiateStreaming(fetch('{{{ TARGET_BASENAME }}}.wasm'), imports)
-  : WebAssembly.instantiate(Module['wasm'], imports)).then(function(output) {
+  : WebAssembly.instantiate(Module['wasm'], imports)).then((output) => {
 #else
-WebAssembly.instantiateStreaming(fetch('{{{ TARGET_BASENAME }}}.wasm'), imports).then(function(output) {
+WebAssembly.instantiateStreaming(fetch('{{{ TARGET_BASENAME }}}.wasm'), imports).then((output) => {
 #endif
 
 #else // Non-streaming instantiation
@@ -137,7 +137,7 @@ WebAssembly.instantiateStreaming(fetch('{{{ TARGET_BASENAME }}}.wasm'), imports)
 if (!Module['wasm']) throw 'Must load WebAssembly Module in to variable Module.wasm before adding compiled output .js script to the DOM';
 #endif
 
-WebAssembly.instantiate(Module['wasm'], imports).then(function(output) {
+WebAssembly.instantiate(Module['wasm'], imports).then((output) => {
 #endif
 
 #if !LibraryManager.has('library_exports.js') && !EMBIND
@@ -237,7 +237,7 @@ WebAssembly.instantiate(Module['wasm'], imports).then(function(output) {
 }
 
 #if ASSERTIONS || WASM == 2
-, function(error) {
+, (error) => {
 #if ASSERTIONS
   console.error(error);
 #endif

src/preamble_minimal.js

@@ -7,13 +7,13 @@
 {{{
   // Helper function to export a symbol on the module object
   // if requested.
-  global.maybeExport = function(x) {
+  global.maybeExport = (x) => {
     return MODULARIZE && EXPORT_ALL ? `Module['${x}'] = ` : '';
   };
   // Export to the AudioWorkletGlobalScope the needed variables to access
   // the heap. AudioWorkletGlobalScope is unable to access global JS vars
   // in the compiled main JS file.
-  global.maybeExportIfAudioWorklet = function(x) {
+  global.maybeExportIfAudioWorklet = (x) => {
     return (MODULARIZE && EXPORT_ALL) || AUDIO_WORKLET ? `Module['${x}'] = ` : '';
   };
   null;

test/code_size/hello_wasm_worker_wasm.js

@@ -45,7 +45,7 @@ WebAssembly.instantiate(b.wasm, {
         },
         a: e
     }
-}).then((function(a) {
+}).then((a => {
     a = a.instance.exports;
     p = a.g;
     q = a.i;

test/code_size/hello_wasm_worker_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 737,
   "a.html.gz": 433,
-  "a.js": 715,
+  "a.js": 707,
   "a.js.gz": 465,
   "a.wasm": 1862,
   "a.wasm.gz": 1040,
-  "total": 3314,
+  "total": 3306,
   "total_gz": 1938
 }

test/code_size/hello_webgl2_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 569,
   "a.html.gz": 379,
-  "a.js": 4971,
-  "a.js.gz": 2430,
+  "a.js": 4963,
+  "a.js.gz": 2432,
   "a.wasm": 10482,
   "a.wasm.gz": 6707,
-  "total": 16022,
-  "total_gz": 9516
+  "total": 16014,
+  "total_gz": 9518
 }

test/code_size/hello_webgl2_wasm2js.json

@@ -1,10 +1,10 @@
 {
   "a.html": 567,
   "a.html.gz": 379,
-  "a.js": 18252,
-  "a.js.gz": 8055,
+  "a.js": 18244,
+  "a.js.gz": 8057,
   "a.mem": 3171,
   "a.mem.gz": 2713,
-  "total": 21990,
-  "total_gz": 11147
+  "total": 21982,
+  "total_gz": 11149
 }

test/code_size/hello_webgl_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 569,
   "a.html.gz": 379,
-  "a.js": 4450,
-  "a.js.gz": 2250,
+  "a.js": 4442,
+  "a.js.gz": 2252,
   "a.wasm": 10482,
   "a.wasm.gz": 6707,
-  "total": 15501,
-  "total_gz": 9336
+  "total": 15493,
+  "total_gz": 9338
 }

test/code_size/hello_webgl_wasm2js.json

@@ -1,10 +1,10 @@
 {
   "a.html": 567,
   "a.html.gz": 379,
-  "a.js": 17724,
-  "a.js.gz": 7870,
+  "a.js": 17716,
+  "a.js.gz": 7871,
   "a.mem": 3171,
   "a.mem.gz": 2713,
-  "total": 21462,
-  "total_gz": 10962
+  "total": 21454,
+  "total_gz": 10963
 }

test/code_size/hello_world_wasm.js

@@ -11,7 +11,7 @@ WebAssembly.instantiate(d.wasm, {
             k.call(c, a);
         }
     }
-}).then((function(a) {
+}).then((a => {
     a = a.instance.exports;
     h = a.d;
     f = a.b;