Make HyKeyword a first class objects

HyKeywords are no longer an instances of string with a particular
prefix, but a completely separate object.

This means keywords no longer trip isinstance str checks, adding a
little bit of type safety to the compiler.

It also means that HyKeywords evaluate to themselves.

Closes hylang#1352

hy/compiler.py

@@ -502,19 +502,18 @@ def _compile_collect(self, exprs, with_kwargs=False, dict_display=False,
                 except StopIteration:
                     raise HyTypeError(expr,
                                       "Keyword argument {kw} needs "
-                                      "a value.".format(kw=str(expr[1:])))
+                                      "a value.".format(kw=expr))
 
-                compiled_value = self.compile(value)
-                ret += compiled_value
-
-                keyword = expr[2:]
-                if not keyword:
+                if not expr:
                     raise HyTypeError(expr, "Can't call a function with the "
                                             "empty keyword")
-                keyword = ast_str(keyword)
 
+                compiled_value = self.compile(value)
+                ret += compiled_value
+
+                arg = str_type(expr)[1:]
                 keywords.append(asty.keyword(
-                    expr, arg=keyword, value=compiled_value.force_expr))
+                    expr, arg=ast_str(arg), value=compiled_value.force_expr))
 
             else:
                 ret += self.compile(expr)
@@ -744,6 +743,9 @@ def _render_quoted_form(self, form, level):
             return imports, HyExpression([HySymbol(name),
                                           HyString(form)]).replace(form), False
 
+        elif isinstance(form, HyKeyword):
+            return imports, form, False
+
         elif isinstance(form, HyString):
             x = [HySymbol(name), form]
             if form.brackets is not None:
@@ -1170,7 +1172,7 @@ def _compile_import(expr, module, names=None, importer=asty.Import):
             if isinstance(iexpr, HyList) and iexpr:
                 module = iexpr.pop(0)
                 entry = iexpr[0]
-                if isinstance(entry, HyKeyword) and entry == HyKeyword(":as"):
+                if entry == HyKeyword(":as"):
                     if not len(iexpr) == 2:
                         raise HyTypeError(iexpr,
                                           "garbage after aliased import")
@@ -1766,7 +1768,7 @@ def compile_expression(self, expression):
         # An exception for pulling together keyword args is if we're doing
         # a typecheck, eg (type :foo)
         with_kwargs = fn not in (
-            "type", "HyKeyword", "keyword", "name", "keyword?")
+            "type", "HyKeyword", "keyword", "name", "keyword?", "identity")
         args, ret, keywords, oldpy_star, oldpy_kw = self._compile_collect(
             expression[1:], with_kwargs, oldpy_unpack=True)
 
@@ -2182,7 +2184,18 @@ def compile_symbol(self, symbol):
 
         return asty.Name(symbol, id=ast_str(symbol), ctx=ast.Load())
 
-    @builds(HyString, HyKeyword, HyBytes)
+    @builds(HyKeyword)
+    def compile_keyword(self, string, building):
+        ret = Result()
+        ret += asty.Call(
+            string,
+            func=asty.Name(string, id="HyKeyword", ctx=ast.Load()),
+            args=[asty.Str(string, s=str_type(string))],
+            keywords=[])
+        ret.add_imports("hy", {"HyKeyword"})
+        return ret
+
+    @builds(HyString, HyBytes)
     def compile_string(self, string, building):
         node = asty.Bytes if PY3 and building is HyBytes else asty.Str
         f = bytes_type if building is HyBytes else str_type

hy/contrib/hy_repr.hy

@@ -32,7 +32,7 @@
 
   (global -quoting)
   (setv started-quoting False)
-  (when (and (not -quoting) (instance? HyObject obj))
+  (when (and (not -quoting) (instance? HyObject obj) (not (instance? HyKeyword obj)))
     (setv -quoting True)
     (setv started-quoting True))
 
@@ -82,10 +82,10 @@
     (+ (get syntax (first x)) (hy-repr (second x)))
     (+ "(" (-cat x) ")"))))
 
-(hy-repr-register HySymbol str)
-(hy-repr-register [str-type bytes-type HyKeyword] (fn [x]
-  (if (and (instance? str-type x) (.startswith x HyKeyword.PREFIX))
-    (return (cut x 1)))
+(hy-repr-register [HySymbol HyKeyword] str)
+(hy-repr-register [str-type bytes-type] (fn [x]
+  (if (and (instance? str-type x) (.startswith x ":"))
+      (return x))
   (setv r (.lstrip (-base-repr x) "ub"))
   (+
     (if (instance? bytes-type x) "b" "")

hy/core/language.hy

@@ -63,8 +63,7 @@
 
 (defn keyword? [k]
   "Check whether `k` is a keyword."
-  (and (instance? (type :foo) k)
-       (.startswith k (get :foo 0))))
+  (instance? HyKeyword k))
 
 (defn dec [n]
   "Decrement `n` by 1."
@@ -458,26 +457,26 @@ as EOF (defaults to an empty string)."
   "Create a keyword from `value`.
 
 Strings numbers and even objects with the __name__ magic will work."
-  (if (and (string? value) (value.startswith HyKeyword.PREFIX))
-    (unmangle value)
-    (if (string? value)
-      (HyKeyword (+ ":" (unmangle value)))
-      (try
-        (unmangle (.__name__ value))
-        (except [] (HyKeyword (+ ":" (string value))))))))
+  (if (keyword? value)
+      (HyKeyword (unmangle value))
+      (if (string? value)
+          (HyKeyword (unmangle value))
+          (try
+            (unmangle (.__name__ value))
+            (except [] (HyKeyword (string value)))))))
 
 (defn name [value]
   "Convert `value` to a string.
 
 Keyword special character will be stripped. String will be used as is.
 Even objects with the __name__ magic will work."
-  (if (and (string? value) (value.startswith HyKeyword.PREFIX))
-    (unmangle (cut value 2))
-    (if (string? value)
-      (unmangle value)
-      (try
-        (unmangle (. value __name__))
-        (except [] (string value))))))
+  (if (keyword? value)
+      (unmangle (cut (str value) 1))
+      (if (string? value)
+          (unmangle value)
+          (try
+            (unmangle (. value __name__))
+            (except [] (string value))))))
 
 (defn xor [a b]
   "Perform exclusive or between `a` and `b`."

hy/models.py

@@ -121,22 +121,39 @@ def __init__(self, string):
 _wrappers[type(None)] = lambda foo: HySymbol("None")
 
 
-class HyKeyword(HyObject, str_type):
+class HyKeyword(HyObject):
     """Generic Hy Keyword object. It's either a ``str`` or a ``unicode``,
     depending on the Python version.
     """
 
-    PREFIX = "\uFDD0"
+    __slots__ = ['_value']
 
-    def __new__(cls, value):
-        if not value.startswith(cls.PREFIX):
-            value = cls.PREFIX + value
-
-        obj = str_type.__new__(cls, value)
-        return obj
+    def __init__(self, value):
+        if value[0] != ':':
+            value = ':' + value
+        self._value = value
 
     def __repr__(self):
-        return "%s(%s)" % (self.__class__.__name__, repr(self[1:]))
+        return "%s(%r)" % (self.__class__.__name__, self._value)
+
+    def __str__(self):
+        return self._value
+
+    def __hash__(self):
+        return hash(self._value)
+
+    def __eq__(self, other):
+        if not isinstance(other, HyKeyword):
+            return NotImplemented
+        return self._value == other._value
+
+    def __ne__(self, other):
+        if not isinstance(other, HyKeyword):
+            return NotImplemented
+        return self._value != other._value
+
+    def __bool__(self):
+        return bool(self._value[1:])
 
 
 def strip_digit_separators(number):

tests/native_tests/language.hy

@@ -552,9 +552,7 @@
   (assert (= (.a.b.meth x) "meth"))
   (assert (= (.a.b.meth x "foo" "bar") "meth foo bar"))
   (assert (= (.a.b.meth :b "1" :a "2" x "foo" "bar") "meth foo bar 2 1"))
-  (assert (= (.a.b.meth x #* ["foo" "bar"]) "meth foo bar"))
-
-  (assert (is (.isdigit :foo) False)))
+  (assert (= (.a.b.meth x #* ["foo" "bar"]) "meth foo bar")))
 
 
 (defn test-do []
@@ -1221,9 +1219,11 @@
   "NATIVE: test if keywords are recognised"
 
   (assert (= :foo :foo))
+  (assert (= :foo ':foo))
   (assert (= (get {:foo "bar"} :foo) "bar"))
   (assert (= (get {:bar "quux"} (get {:foo :bar} :foo)) "quux")))
 
+
 (defn test-keyword-clash []
   "NATIVE: test that keywords do not clash with normal strings"
 
@@ -1646,11 +1646,6 @@ macros()
   (setv (. foo [1] test) "hello")
   (assert (= (getattr (. foo [1]) "test") "hello")))
 
-(defn test-keyword-quoting []
-  "NATIVE: test keyword quoting magic"
-  (assert (= :foo "\ufdd0:foo"))
-  (assert (= `:foo "\ufdd0:foo")))
-
 (defn test-only-parse-lambda-list-in-defn []
   "NATIVE: test lambda lists are only parsed in defn"
   (try