diff --git a/mypy/checker.py b/mypy/checker.py
index 065758cd2be9..61104756b297 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -2178,7 +2178,7 @@ def visit_class_def(self, defn: ClassDef) -> None:
                     temp = self.temp_node(sig, context=decorator)
                     fullname = None
                     if isinstance(decorator, RefExpr):
-                        fullname = decorator.fullname
+                        fullname = decorator.fullname or None
 
                     # TODO: Figure out how to have clearer error messages.
                     # (e.g. "class decorator must be a function that accepts a type."
@@ -4598,7 +4598,7 @@ def visit_decorator(self, e: Decorator) -> None:
             temp = self.temp_node(sig, context=e)
             fullname = None
             if isinstance(d, RefExpr):
-                fullname = d.fullname
+                fullname = d.fullname or None
             # if this is a expression like @b.a where b is an object, get the type of b
             # so we can pass it the method hook in the plugins
             object_type: Type | None = None
diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index e6634e124d30..1c25b8ea7a12 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -216,8 +216,8 @@ def extract_refexpr_names(expr: RefExpr) -> set[str]:
     Note that currently, the only two subclasses of RefExpr are NameExpr and
     MemberExpr."""
     output: set[str] = set()
-    while isinstance(expr.node, MypyFile) or expr.fullname is not None:
-        if isinstance(expr.node, MypyFile) and expr.fullname is not None:
+    while isinstance(expr.node, MypyFile) or expr.fullname:
+        if isinstance(expr.node, MypyFile) and expr.fullname:
             # If it's None, something's wrong (perhaps due to an
             # import cycle or a suppressed error).  For now we just
             # skip it.
@@ -228,7 +228,7 @@ def extract_refexpr_names(expr: RefExpr) -> set[str]:
             if isinstance(expr.node, TypeInfo):
                 # Reference to a class or a nested class
                 output.update(split_module_names(expr.node.module_name))
-            elif expr.fullname is not None and "." in expr.fullname and not is_suppressed_import:
+            elif "." in expr.fullname and not is_suppressed_import:
                 # Everything else (that is not a silenced import within a class)
                 output.add(expr.fullname.rsplit(".", 1)[0])
             break
@@ -526,7 +526,7 @@ def visit_call_expr_inner(self, e: CallExpr, allow_none_return: bool = False) ->
             # There are two special cases where plugins might act:
             # * A "static" reference/alias to a class or function;
             #   get_function_hook() will be invoked for these.
-            fullname = e.callee.fullname
+            fullname = e.callee.fullname or None
             if isinstance(e.callee.node, TypeAlias):
                 target = get_proper_type(e.callee.node.target)
                 if isinstance(target, Instance):
@@ -536,7 +536,7 @@ def visit_call_expr_inner(self, e: CallExpr, allow_none_return: bool = False) ->
             #   get_method_hook() and get_method_signature_hook() will
             #   be invoked for these.
             if (
-                fullname is None
+                not fullname
                 and isinstance(e.callee, MemberExpr)
                 and self.chk.has_type(e.callee.expr)
             ):
@@ -605,7 +605,7 @@ def method_fullname(self, object_type: Type, method_name: str) -> str | None:
         elif isinstance(object_type, TupleType):
             type_name = tuple_fallback(object_type).type.fullname
 
-        if type_name is not None:
+        if type_name:
             return f"{type_name}.{method_name}"
         else:
             return None
@@ -5489,7 +5489,7 @@ def type_info_from_type(typ: Type) -> TypeInfo | None:
 
 
 def is_operator_method(fullname: str | None) -> bool:
-    if fullname is None:
+    if not fullname:
         return False
     short_name = fullname.split(".")[-1]
     return (
diff --git a/mypy/nodes.py b/mypy/nodes.py
index 80ab787f4a9c..85bb9ce4a8de 100644
--- a/mypy/nodes.py
+++ b/mypy/nodes.py
@@ -25,7 +25,6 @@
 from mypy_extensions import trait
 
 import mypy.strconv
-from mypy.bogus_type import Bogus
 from mypy.util import short_type
 from mypy.visitor import ExpressionVisitor, NodeVisitor, StatementVisitor
 
@@ -247,12 +246,10 @@ class SymbolNode(Node):
     def name(self) -> str:
         pass
 
-    # fullname can often be None even though the type system
-    # disagrees. We mark this with Bogus to let mypyc know not to
-    # worry about it.
+    # Fully qualified name
     @property
     @abstractmethod
-    def fullname(self) -> Bogus[str]:
+    def fullname(self) -> str:
         pass
 
     @abstractmethod
@@ -294,7 +291,7 @@ class MypyFile(SymbolNode):
     __match_args__ = ("name", "path", "defs")
 
     # Fully qualified module name
-    _fullname: Bogus[str]
+    _fullname: str
     # Path to the file (empty string if not known)
     path: str
     # Top-level definitions and statements
@@ -361,7 +358,7 @@ def name(self) -> str:
         return "" if not self._fullname else self._fullname.split(".")[-1]
 
     @property
-    def fullname(self) -> Bogus[str]:
+    def fullname(self) -> str:
         return self._fullname
 
     def accept(self, visitor: NodeVisitor[T]) -> T:
@@ -526,8 +523,7 @@ def __init__(self) -> None:
         self.is_static = False
         self.is_final = False
         # Name with module prefix
-        # TODO: Type should be Optional[str]
-        self._fullname = cast(Bogus[str], None)
+        self._fullname = ""
 
     @property
     @abstractmethod
@@ -535,7 +531,7 @@ def name(self) -> str:
         pass
 
     @property
-    def fullname(self) -> Bogus[str]:
+    def fullname(self) -> str:
         return self._fullname
 
 
@@ -871,7 +867,7 @@ def name(self) -> str:
         return self.func.name
 
     @property
-    def fullname(self) -> Bogus[str]:
+    def fullname(self) -> str:
         return self.func.fullname
 
     @property
@@ -967,7 +963,7 @@ def __init__(self, name: str, type: mypy.types.Type | None = None) -> None:
         super().__init__()
         self._name = name  # Name without module prefix
         # TODO: Should be Optional[str]
-        self._fullname = cast("Bogus[str]", None)  # Name with module prefix
+        self._fullname = ""  # Name with module prefix
         # TODO: Should be Optional[TypeInfo]
         self.info = VAR_NO_INFO
         self.type: mypy.types.Type | None = type  # Declared or inferred type, or None
@@ -1019,7 +1015,7 @@ def name(self) -> str:
         return self._name
 
     @property
-    def fullname(self) -> Bogus[str]:
+    def fullname(self) -> str:
         return self._fullname
 
     def accept(self, visitor: NodeVisitor[T]) -> T:
@@ -1057,7 +1053,7 @@ class ClassDef(Statement):
 
     __slots__ = (
         "name",
-        "fullname",
+        "_fullname",
         "defs",
         "type_vars",
         "base_type_exprs",
@@ -1075,7 +1071,7 @@ class ClassDef(Statement):
     __match_args__ = ("name", "defs")
 
     name: str  # Name of the class without module prefix
-    fullname: Bogus[str]  # Fully qualified name of the class
+    _fullname: str  # Fully qualified name of the class
     defs: Block
     type_vars: list[mypy.types.TypeVarLikeType]
     # Base class expressions (not semantically analyzed -- can be arbitrary expressions)
@@ -1102,7 +1098,7 @@ def __init__(
     ) -> None:
         super().__init__()
         self.name = name
-        self.fullname = None  # type: ignore[assignment]
+        self._fullname = ""
         self.defs = defs
         self.type_vars = type_vars or []
         self.base_type_exprs = base_type_exprs or []
@@ -1117,6 +1113,14 @@ def __init__(
         self.deco_line: int | None = None
         self.removed_statements = []
 
+    @property
+    def fullname(self) -> str:
+        return self._fullname
+
+    @fullname.setter
+    def fullname(self, v: str) -> None:
+        self._fullname = v
+
     def accept(self, visitor: StatementVisitor[T]) -> T:
         return visitor.visit_class_def(self)
 
@@ -1725,7 +1729,7 @@ class RefExpr(Expression):
     __slots__ = (
         "kind",
         "node",
-        "fullname",
+        "_fullname",
         "is_new_def",
         "is_inferred_def",
         "is_alias_rvalue",
@@ -1739,7 +1743,7 @@ def __init__(self) -> None:
         # Var, FuncDef or TypeInfo that describes this
         self.node: SymbolNode | None = None
         # Fully qualified name (or name if not global)
-        self.fullname: str | None = None
+        self._fullname = ""
         # Does this define a new name?
         self.is_new_def = False
         # Does this define a new name with inferred type?
@@ -1752,6 +1756,14 @@ def __init__(self) -> None:
         # Cache type guard from callable_type.type_guard
         self.type_guard: mypy.types.Type | None = None
 
+    @property
+    def fullname(self) -> str:
+        return self._fullname
+
+    @fullname.setter
+    def fullname(self, v: str) -> None:
+        self._fullname = v
+
 
 class NameExpr(RefExpr):
     """Name expression
@@ -2806,7 +2818,7 @@ class is generic then it will be a type constructor of higher kind.
         "self_type",
     )
 
-    _fullname: Bogus[str]  # Fully qualified name
+    _fullname: str  # Fully qualified name
     # Fully qualified name for the module this type was defined in. This
     # information is also in the fullname, but is harder to extract in the
     # case of nested class definitions.
@@ -3023,7 +3035,7 @@ def name(self) -> str:
         return self.defn.name
 
     @property
-    def fullname(self) -> Bogus[str]:
+    def fullname(self) -> str:
         return self._fullname
 
     def is_generic(self) -> bool:
@@ -3739,11 +3751,7 @@ def serialize(self, prefix: str, name: str) -> JsonDict:
             if prefix is not None:
                 fullname = self.node.fullname
                 if (
-                    # See the comment above SymbolNode.fullname -- fullname can often be None,
-                    # but for complex reasons it's annotated as being `Bogus[str]` instead of `str | None`,
-                    # meaning mypy erroneously thinks the `fullname is not None` check here is redundant
-                    fullname is not None  # type: ignore[redundant-expr]
-                    and "." in fullname
+                    "." in fullname
                     and fullname != prefix + "." + name
                     and not (isinstance(self.node, Var) and self.node.from_module_getattr)
                 ):
diff --git a/mypy/partially_defined.py b/mypy/partially_defined.py
index c63c62c3e393..9a58df04371f 100644
--- a/mypy/partially_defined.py
+++ b/mypy/partially_defined.py
@@ -287,7 +287,7 @@ def is_undefined(self, name: str) -> bool:
 
 
 def refers_to_builtin(o: RefExpr) -> bool:
-    return o.fullname is not None and o.fullname.startswith("builtins.")
+    return o.fullname.startswith("builtins.")
 
 
 class Loop:
diff --git a/mypy/semanal.py b/mypy/semanal.py
index aee355d7880d..acc485a609e0 100644
--- a/mypy/semanal.py
+++ b/mypy/semanal.py
@@ -3022,13 +3022,13 @@ def analyze_lvalues(self, s: AssignmentStmt) -> None:
     def apply_dynamic_class_hook(self, s: AssignmentStmt) -> None:
         if not isinstance(s.rvalue, CallExpr):
             return
-        fname = None
+        fname = ""
         call = s.rvalue
         while True:
             if isinstance(call.callee, RefExpr):
                 fname = call.callee.fullname
             # check if method call
-            if fname is None and isinstance(call.callee, MemberExpr):
+            if not fname and isinstance(call.callee, MemberExpr):
                 callee_expr = call.callee.expr
                 if isinstance(callee_expr, RefExpr) and callee_expr.fullname:
                     method_name = call.callee.name
@@ -4624,7 +4624,7 @@ def bind_name_expr(self, expr: NameExpr, sym: SymbolTableNode) -> None:
         else:
             expr.kind = sym.kind
             expr.node = sym.node
-            expr.fullname = sym.fullname
+            expr.fullname = sym.fullname or ""
 
     def visit_super_expr(self, expr: SuperExpr) -> None:
         if not self.type and not expr.call.args:
@@ -4849,7 +4849,7 @@ def visit_member_expr(self, expr: MemberExpr) -> None:
                     self.process_placeholder(expr.name, "attribute", expr)
                     return
                 expr.kind = sym.kind
-                expr.fullname = sym.fullname
+                expr.fullname = sym.fullname or ""
                 expr.node = sym.node
         elif isinstance(base, RefExpr):
             # This branch handles the case C.bar (or cls.bar or self.bar inside
@@ -4881,7 +4881,7 @@ def visit_member_expr(self, expr: MemberExpr) -> None:
                     if not n:
                         return
                     expr.kind = n.kind
-                    expr.fullname = n.fullname
+                    expr.fullname = n.fullname or ""
                     expr.node = n.node
 
     def visit_op_expr(self, expr: OpExpr) -> None:
@@ -5341,7 +5341,7 @@ def is_overloaded_item(self, node: SymbolNode, statement: Statement) -> bool:
         return False
 
     def is_defined_in_current_module(self, fullname: str | None) -> bool:
-        if fullname is None:
+        if not fullname:
             return False
         return module_prefix(self.modules, fullname) == self.cur_mod_id
 
diff --git a/mypy/server/aststrip.py b/mypy/server/aststrip.py
index b0666f8e1ff4..05af6a3d53a1 100644
--- a/mypy/server/aststrip.py
+++ b/mypy/server/aststrip.py
@@ -230,7 +230,7 @@ def visit_op_expr(self, node: OpExpr) -> None:
     def strip_ref_expr(self, node: RefExpr) -> None:
         node.kind = None
         node.node = None
-        node.fullname = None
+        node.fullname = ""
         node.is_new_def = False
         node.is_inferred_def = False
 
diff --git a/mypy/server/deps.py b/mypy/server/deps.py
index eb40737061bf..50b66b70b8aa 100644
--- a/mypy/server/deps.py
+++ b/mypy/server/deps.py
@@ -289,13 +289,9 @@ def visit_decorator(self, o: Decorator) -> None:
             # all call sites, making them all `Any`.
             for d in o.decorators:
                 tname: str | None = None
-                if isinstance(d, RefExpr) and d.fullname is not None:
+                if isinstance(d, RefExpr) and d.fullname:
                     tname = d.fullname
-                if (
-                    isinstance(d, CallExpr)
-                    and isinstance(d.callee, RefExpr)
-                    and d.callee.fullname is not None
-                ):
+                if isinstance(d, CallExpr) and isinstance(d.callee, RefExpr) and d.callee.fullname:
                     tname = d.callee.fullname
                 if tname is not None:
                     self.add_dependency(make_trigger(tname), make_trigger(o.func.fullname))
@@ -500,7 +496,7 @@ def visit_assignment_stmt(self, o: AssignmentStmt) -> None:
             if (
                 isinstance(rvalue, CallExpr)
                 and isinstance(rvalue.callee, RefExpr)
-                and rvalue.callee.fullname is not None
+                and rvalue.callee.fullname
             ):
                 fname: str | None = None
                 if isinstance(rvalue.callee.node, TypeInfo):
@@ -510,7 +506,7 @@ def visit_assignment_stmt(self, o: AssignmentStmt) -> None:
                         fname = init.node.fullname
                 else:
                     fname = rvalue.callee.fullname
-                if fname is None:
+                if not fname:
                     return
                 for lv in o.lvalues:
                     if isinstance(lv, RefExpr) and lv.fullname and lv.is_new_def:
@@ -638,7 +634,7 @@ def visit_del_stmt(self, o: DelStmt) -> None:
     # Expressions
 
     def process_global_ref_expr(self, o: RefExpr) -> None:
-        if o.fullname is not None:
+        if o.fullname:
             self.add_dependency(make_trigger(o.fullname))
 
         # If this is a reference to a type, generate a dependency to its
diff --git a/mypy/strconv.py b/mypy/strconv.py
index 861a7c9b7fa0..b2e9da5dbf6a 100644
--- a/mypy/strconv.py
+++ b/mypy/strconv.py
@@ -367,7 +367,7 @@ def pretty_name(
             id = ""
         if isinstance(target_node, mypy.nodes.MypyFile) and name == fullname:
             n += id
-        elif kind == mypy.nodes.GDEF or (fullname != name and fullname is not None):
+        elif kind == mypy.nodes.GDEF or (fullname != name and fullname):
             # Append fully qualified name for global references.
             n += f" [{fullname}{id}]"
         elif kind == mypy.nodes.LDEF:
diff --git a/mypy/stubtest.py b/mypy/stubtest.py
index bfd8e2b9c81a..774f03cbbdd0 100644
--- a/mypy/stubtest.py
+++ b/mypy/stubtest.py
@@ -1147,7 +1147,7 @@ def apply_decorator_to_funcitem(
     ) -> nodes.FuncItem | None:
         if not isinstance(decorator, nodes.RefExpr):
             return None
-        if decorator.fullname is None:
+        if not decorator.fullname:
             # Happens with namedtuple
             return None
         if (
diff --git a/mypy/test/testsemanal.py b/mypy/test/testsemanal.py
index 6cfd53f09beb..71ebc43df8c2 100644
--- a/mypy/test/testsemanal.py
+++ b/mypy/test/testsemanal.py
@@ -202,7 +202,7 @@ def run_case(self, testcase: DataDrivenTestCase) -> None:
             for f in result.files.values():
                 for n in f.names.values():
                     if isinstance(n.node, TypeInfo):
-                        assert n.fullname is not None
+                        assert n.fullname
                         typeinfos[n.fullname] = n.node
 
             # The output is the symbol table converted into a string.
diff --git a/mypy/tvar_scope.py b/mypy/tvar_scope.py
index db83768bf68a..9b432d8e68ec 100644
--- a/mypy/tvar_scope.py
+++ b/mypy/tvar_scope.py
@@ -129,7 +129,7 @@ def bind_existing(self, tvar_def: TypeVarLikeType) -> None:
 
     def get_binding(self, item: str | SymbolTableNode) -> TypeVarLikeType | None:
         fullname = item.fullname if isinstance(item, SymbolTableNode) else item
-        assert fullname is not None
+        assert fullname
         if fullname in self.scope:
             return self.scope[fullname]
         elif self.parent is not None:
diff --git a/mypy/typeanal.py b/mypy/typeanal.py
index df74344fb392..07720afeff88 100644
--- a/mypy/typeanal.py
+++ b/mypy/typeanal.py
@@ -1123,7 +1123,7 @@ def visit_type_type(self, t: TypeType) -> Type:
         return TypeType.make_normalized(self.anal_type(t.item), line=t.line)
 
     def visit_placeholder_type(self, t: PlaceholderType) -> Type:
-        n = None if t.fullname is None else self.api.lookup_fully_qualified(t.fullname)
+        n = None if not t.fullname else self.api.lookup_fully_qualified(t.fullname)
         if not n or isinstance(n.node, PlaceholderNode):
             self.api.defer()  # Still incomplete
             return t
diff --git a/mypyc/irbuild/builder.py b/mypyc/irbuild/builder.py
index c24207ac64ec..f2a70d4e8691 100644
--- a/mypyc/irbuild/builder.py
+++ b/mypyc/irbuild/builder.py
@@ -1001,7 +1001,7 @@ def call_refexpr_with_args(
     ) -> Value:
 
         # Handle data-driven special-cased primitive call ops.
-        if callee.fullname is not None and expr.arg_kinds == [ARG_POS] * len(arg_values):
+        if callee.fullname and expr.arg_kinds == [ARG_POS] * len(arg_values):
             call_c_ops_candidates = function_ops.get(callee.fullname, [])
             target = self.builder.matching_call_c(
                 call_c_ops_candidates, arg_values, expr.line, self.node_type(expr)
@@ -1026,7 +1026,7 @@ def call_refexpr_with_args(
             callee_node = callee_node.func
         if (
             callee_node is not None
-            and callee.fullname is not None
+            and callee.fullname
             and callee_node in self.mapper.func_to_decl
             and all(kind in (ARG_POS, ARG_NAMED) for kind in expr.arg_kinds)
         ):
@@ -1240,7 +1240,7 @@ def load_global(self, expr: NameExpr) -> Value:
             and isinstance(expr.node, TypeInfo)
             and not self.is_synthetic_type(expr.node)
         ):
-            assert expr.fullname is not None
+            assert expr.fullname
             return self.load_native_type_object(expr.fullname)
         return self.load_global_str(expr.name, expr.line)
 
diff --git a/mypyc/irbuild/function.py b/mypyc/irbuild/function.py
index 5447f945db25..523f8c299c2f 100644
--- a/mypyc/irbuild/function.py
+++ b/mypyc/irbuild/function.py
@@ -789,7 +789,7 @@ def load_type(builder: IRBuilder, typ: TypeInfo, line: int) -> Value:
 
 
 def load_func(builder: IRBuilder, func_name: str, fullname: str | None, line: int) -> Value:
-    if fullname is not None and not fullname.startswith(builder.current_module):
+    if fullname and not fullname.startswith(builder.current_module):
         # we're calling a function in a different module
 
         # We can't use load_module_attr_by_fullname here because we need to load the function using
diff --git a/test-data/unit/plugins/customentry.py b/test-data/unit/plugins/customentry.py
index f8b86c33dcfc..b3dacfd4cf44 100644
--- a/test-data/unit/plugins/customentry.py
+++ b/test-data/unit/plugins/customentry.py
@@ -4,7 +4,7 @@ class MyPlugin(Plugin):
     def get_function_hook(self, fullname):
         if fullname == '__main__.f':
             return my_hook
-        assert fullname is not None
+        assert fullname
         return None
 
 def my_hook(ctx):