Add param names for str.encode and decode

src/runtime/code.cpp

@@ -129,6 +129,9 @@ BoxedCode::BoxedCode(int num_args, bool takes_varargs, bool takes_kwargs, int fi
       num_args(num_args),
       times_interpreted(0),
       internal_callable(NULL, NULL) {
+    // If any param names are specified, make sure all of them are (to avoid common mistakes):
+    ASSERT(this->param_names.numNormalArgs() == 0 || this->param_names.numNormalArgs() == num_args, "%d %d",
+           this->param_names.numNormalArgs(), num_args);
 }
 
 BoxedCode::BoxedCode(int num_args, bool takes_varargs, bool takes_kwargs, const char* name, const char* doc,

src/runtime/str.cpp

@@ -2741,12 +2741,14 @@ void setupStr() {
     str_cls->giveAttr("istitle", new BoxedFunction(BoxedCode::create((void*)strIsTitle, BOXED_BOOL, 1, "str.istitle")));
     str_cls->giveAttr("isupper", new BoxedFunction(BoxedCode::create((void*)strIsUpper, BOXED_BOOL, 1, "str.isupper")));
 
-    str_cls->giveAttr(
-        "decode",
-        new BoxedFunction(BoxedCode::create((void*)strDecode, UNKNOWN, 3, false, false, "str.decode"), { 0, 0 }));
-    str_cls->giveAttr(
-        "encode",
-        new BoxedFunction(BoxedCode::create((void*)strEncode, UNKNOWN, 3, false, false, "str.encode"), { 0, 0 }));
+    str_cls->giveAttr("decode",
+                      new BoxedFunction(BoxedCode::create((void*)strDecode, UNKNOWN, 3, false, false, "str.decode", "",
+                                                          ParamNames({ "", "encoding", "errors" }, NULL, NULL)),
+                                        { 0, 0 }));
+    str_cls->giveAttr("encode",
+                      new BoxedFunction(BoxedCode::create((void*)strEncode, UNKNOWN, 3, false, false, "str.encode", "",
+                                                          ParamNames({ "", "encoding", "errors" }, NULL, NULL)),
+                                        { 0, 0 }));
 
     str_cls->giveAttr("lower", new BoxedFunction(BoxedCode::create((void*)strLower, STR, 1, "str.lower")));
     str_cls->giveAttr("swapcase", new BoxedFunction(BoxedCode::create((void*)strSwapcase, STR, 1, "str.swapcase")));