Revert attempt to fix Mapping.get

Author: sterliakov

mypy/checkexpr.py

@@ -139,7 +139,6 @@
     get_all_type_vars,
     get_type_vars,
     is_literal_type_like,
-    is_literal_type_like_or_singleton,
     make_simplified_union,
     simple_literal_type,
     true_only,
@@ -2043,7 +2042,7 @@ def infer_function_type_arguments_using_context(
             #        expects_literal(identity(3))  # Should type-check
             # TODO: we may want to add similar exception if all arguments are lambdas, since
             # in this case external context is almost everything we have.
-            if not is_generic_instance(ctx) and not is_literal_type_like_or_singleton(ctx):
+            if not is_generic_instance(ctx) and not is_literal_type_like(ctx):
                 return callable.copy_modified()
         args = infer_type_arguments(
             callable.variables, ret_type, erased_ctx, skip_unsatisfied=True

mypy/typeops.py

@@ -1005,27 +1005,6 @@ def is_literal_type_like(t: Type | None) -> bool:
         return False
 
 
-def is_literal_type_like_or_singleton(t: Type | None) -> bool:
-    """Returns 'true' if the given type context is potentially either a LiteralType,
-    a Union of LiteralType, a singleton (or a union thereof), or something similar.
-    """
-    t = get_proper_type(t)
-    if t is None:
-        return False
-    elif isinstance(t, LiteralType):
-        return True
-    elif t.is_singleton_type():
-        return True
-    elif isinstance(t, UnionType):
-        return any(is_literal_type_like_or_singleton(item) for item in t.items)
-    elif isinstance(t, TypeVarType):
-        return is_literal_type_like_or_singleton(t.upper_bound) or any(
-            is_literal_type_like_or_singleton(item) for item in t.values
-        )
-    else:
-        return False
-
-
 def is_singleton_type(typ: Type) -> bool:
     """Returns 'true' if this type is a "singleton type" -- if there exists
     exactly only one runtime value associated with this type.

test-data/unit/check-inference-context.test

@@ -1511,18 +1511,14 @@ def check(paths: Iterable[str], key: Callable[[str], int]) -> Union[str, None]:
     return mymin(paths, key=key, default=None)
 [builtins fixtures/tuple.pyi]
 
-[case testInferenceContextLiteralInstance]
-from collections.abc import Callable, Iterable, Mapping
-from enum import Enum
-from typing import Final, Generic, Literal, TypeVar, Union
-
-class Opt(Enum):
-    MISSING = "MISSING"
+[case testInferenceContextMappingGet-xfail]
+from collections.abc import Mapping
+from typing import TypeVar, Union
 
-MISSING: Final[Literal[Opt.MISSING]] = Opt.MISSING
 _T1 = TypeVar("_T1")
 
 def check(mapping: Mapping[str, _T1]) -> None:
-    res: Union[_T1, Opt] = mapping.get("", MISSING)
+    fail1 = mapping.get("", "")
+    fail2: Union[_T1, str] = mapping.get("", "")
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-full.pyi]