LibJS: Make indirect bindings of module behave like normal bindings

Before this we attempted to hack around this by only overriding
has_binding. However this did not cover all cases, for example when
assigning to variables before their declaration it didn't throw.
By using the new find_binding_and_index virtual method we can just
pretend the indirect bindings are real.

Since indirect binding do come from a normal environment we need to
ensure you cannot modify the binding and that properties like mutable
are false as expected by the spec for such an indirect binding.

1 files changed, 23 insertions, 0 deletions

diff --git a/Userland/Libraries/LibJS/Tests/modules/accessing-lex-import-before-decl.mjs b/Userland/Libraries/LibJS/Tests/modules/accessing-lex-import-before-decl.mjs
new file mode 100644
index 0000000000..1b96bf8aef
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/modules/accessing-lex-import-before-decl.mjs
@@ -0,0 +1,23 @@
+let passed = true;
+
+try {
+    importedLexVariable;
+    passed = false;
+} catch (e) {
+    if (!(e instanceof ReferenceError))
+        throw new Error("Expected importedLexVariable; to throw ReferenceError got " + e);
+}
+
+try {
+    // Even though value is let, this should still throw TypeError because it is immutable!
+    importedLexVariable = 0;
+    passed = false;
+} catch (e) {
+    if (!(e instanceof TypeError))
+        throw new Error("Expected importedLexVariable = 0; to throw TypeError got " + e);
+}
+
+import { value as importedLexVariable } from "./accessing-lex-import-before-decl.mjs";
+export let value = 123;
+
+export { passed };