Improve representation of KnownValue of type, function, module (#788)

docs/changelog.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Improve representation of known module, function, and type objects
+  in error messages (#788)
 - Add a mechanism to allow overriding the global variables in an
   analyzed module. Use this mechanism to set the type of
   `qcore.testing.Anything` to `Any`. (#786)

pyanalyze/test_value.py

@@ -62,8 +62,16 @@ def test_any_value() -> None:
 def test_known_value() -> None:
     val = KnownValue(3)
     assert 3 == val.val
-    assert "Literal[3]" == str(val)
-    assert "Literal['']" == str(KnownValue(""))
+    assert str(val) == "Literal[3]"
+    assert str(KnownValue("")) == "Literal['']"
+    assert str(KnownValue(None)) == "None"
+    assert str(KnownValue(str)) == "type 'str'"
+    assert str(KnownValue(KnownValue)) == "type 'pyanalyze.value.KnownValue'"
+    assert (
+        str(KnownValue(test_known_value))
+        == "function 'pyanalyze.test_value.test_known_value'"
+    )
+    assert str(KnownValue(ast)) == "module 'ast'"
     assert val.is_type(int)
     assert not val.is_type(str)
 

pyanalyze/value.py

@@ -26,7 +26,7 @@ def function(x: int, y: list[int], z: Any):
 from collections import deque
 from dataclasses import InitVar, dataclass, field
 from itertools import chain
-from types import FunctionType
+from types import FunctionType, ModuleType
 from typing import (
     Any,
     Callable,
@@ -583,6 +583,12 @@ def __hash__(self) -> int:
     def __str__(self) -> str:
         if self.val is None:
             return "None"
+        elif isinstance(self.val, ModuleType):
+            return f"module {self.val.__name__!r}"
+        elif isinstance(self.val, FunctionType):
+            return f"function {get_fully_qualified_name(self.val)!r}"
+        elif isinstance(self.val, type):
+            return f"type {get_fully_qualified_name(self.val)!r}"
         else:
             return f"Literal[{self.val!r}]"
 
@@ -601,6 +607,18 @@ def simplify(self) -> Value:
         return val.simplify()
 
 
+def get_fully_qualified_name(obj: Union[FunctionType, type]) -> str:
+    mod = getattr(obj, "__module__", None)
+    if mod == "builtins":
+        mod = None
+    name = getattr(obj, "__qualname__", None)
+    if name is None:
+        return repr(obj)
+    if mod:
+        return f"{mod}.{name}"
+    return name
+
+
 @dataclass(frozen=True)
 class KnownValueWithTypeVars(KnownValue):
     """Subclass of KnownValue that records a TypeVar substitution."""