Tests for IO.read().

src/wren_core.c

@@ -1202,7 +1202,7 @@ void wrenInitializeCore(WrenVM* vm)
   vm->numClass->name->obj.classObj = vm->stringClass;
   vm->stringClass->name->obj.classObj = vm->stringClass;
 
-  wrenInterpret(vm, "Wren core library", libSource);
+  wrenInterpret(vm, "", libSource);
 
   vm->listClass = AS_CLASS(findGlobal(vm, "List"));
   NATIVE(vm->listClass->obj.classObj, " instantiate", list_instantiate);

src/wren_debug.c

@@ -19,6 +19,12 @@ void wrenDebugPrintStackTrace(WrenVM* vm, ObjFiber* fiber)
       fn = ((ObjClosure*)frame->fn)->fn;
     }
 
+    // Built-in libraries have no source path and are explicitly omitted from
+    // stack traces since we don't want to highlight to a user the
+    // implementation detail of what part of a core library is implemented in
+    // C and what is in Wren.
+    if (fn->debug->sourcePath->length == 0) continue;
+
     // - 1 because IP has advanced past the instruction that it just executed.
     int line = fn->debug->sourceLines[frame->ip - fn->bytecode - 1];
     fprintf(stderr, "[%s line %d] in %s\n",

src/wren_io.c

@@ -93,6 +93,7 @@ static const char* libSource =
 "  }\n"
 "\n"
 "  static read(prompt) {\n"
+"    if (!(prompt is String)) Fiber.abort(\"Prompt must be a string.\")\n"
 "    IO.write(prompt)\n"
 "    return IO.read\n"
 "  }\n"
@@ -133,7 +134,7 @@ static void ioClock(WrenVM* vm)
 
 void wrenLoadIOLibrary(WrenVM* vm)
 {
-  wrenInterpret(vm, "Wren IO library", libSource);
+  wrenInterpret(vm, "", libSource);
   wrenDefineStaticMethod(vm, "IO", "writeString_", 1, ioWriteString);
   wrenDefineStaticMethod(vm, "IO", "clock", 0, ioClock);
   wrenDefineStaticMethod(vm, "IO", "read", 0, ioRead);