JS optimizer: Fix scoping issues with non-defined functions

test/js_optimizer/emitDCEGraph-scopes-output.js

@@ -0,0 +1,23 @@
+[
+ {
+  "name": "emcc$defun$arrowed",
+  "reaches": [],
+  "root": true
+ },
+ {
+  "name": "emcc$defun$bar",
+  "reaches": [],
+  "root": true
+ },
+ {
+  "name": "emcc$defun$caller",
+  "reaches": [
+   "emcc$defun$foo"
+  ],
+  "root": true
+ },
+ {
+  "name": "emcc$defun$foo",
+  "reaches": []
+ }
+]

test/js_optimizer/emitDCEGraph-scopes.js

@@ -0,0 +1,33 @@
+function foo() {}
+
+function bar() {}
+
+// caller() calls foo(). There is also another function called "caller", down
+// below, which should not confuse us (if it does, nothing would refer to foo,
+// and instead we'd think the toplevel caller calls bar).
+function caller() {
+  foo();
+}
+
+caller();
+
+var object = {
+  method() {
+    function caller(data) {
+      bar();
+    }
+  }
+};
+
+// Similar, with an arrow function. This should also not confuse us (it would
+// make "caller" refer to "arrowed".
+
+function arrowed() {}
+
+var arrow = () => {
+  function caller(data) {
+    arrowed();
+  }
+}
+
+wasmImports = {};

test/test_other.py

@@ -2896,6 +2896,7 @@ def test_extern_prepost(self):
     'emitDCEGraph3': (['emitDCEGraph', '--no-print'],),
     'emitDCEGraph4': (['emitDCEGraph', '--no-print'],),
     'emitDCEGraph5': (['emitDCEGraph', '--no-print'],),
+    'emitDCEGraph-scopes': (['emitDCEGraph', '--no-print'],),
     'minimal-runtime-applyDCEGraphRemovals': (['applyDCEGraphRemovals'],),
     'applyDCEGraphRemovals': (['applyDCEGraphRemovals'],),
     'applyImportAndExportNameChanges': (['applyImportAndExportNameChanges'],),