diff --git a/mypy/checker.py b/mypy/checker.py
index 3b48f66fc3b5..e4b52cfdc6ba 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -12,6 +12,7 @@
 import mypy.checkexpr
 from mypy import errorcodes as codes, join, message_registry, nodes, operators
 from mypy.binder import ConditionalTypeBinder, Frame, get_declaration
+from mypy.checker_shared import CheckerScope, TypeCheckerSharedApi, TypeRange
 from mypy.checkmember import (
     MemberContext,
     analyze_class_attribute_access,
@@ -126,7 +127,7 @@
 from mypy.operators import flip_ops, int_op_to_method, neg_ops
 from mypy.options import PRECISE_TUPLE_TYPES, Options
 from mypy.patterns import AsPattern, StarredPattern
-from mypy.plugin import CheckerPluginInterface, Plugin
+from mypy.plugin import Plugin
 from mypy.plugins import dataclasses as dataclasses_plugin
 from mypy.scope import Scope
 from mypy.semanal import is_trivial_body, refers_to_fullname, set_callable_name
@@ -259,13 +260,6 @@ class FineGrainedDeferredNode(NamedTuple):
 TypeMap: _TypeAlias = Optional[dict[Expression, Type]]
 
 
-# An object that represents either a precise type or a type with an upper bound;
-# it is important for correct type inference with isinstance.
-class TypeRange(NamedTuple):
-    item: Type
-    is_upper_bound: bool  # False => precise type
-
-
 # Keeps track of partial types in a single scope. In fine-grained incremental
 # mode partial types initially defined at the top level cannot be completed in
 # a function, and we use the 'is_function' attribute to enforce this.
@@ -275,7 +269,7 @@ class PartialTypeScope(NamedTuple):
     is_local: bool
 
 
-class TypeChecker(NodeVisitor[None], CheckerPluginInterface):
+class TypeChecker(NodeVisitor[None], TypeCheckerSharedApi):
     """Mypy type checker.
 
     Type check mypy source files that have been semantically analyzed.
@@ -302,7 +296,7 @@ class TypeChecker(NodeVisitor[None], CheckerPluginInterface):
     # Helper for managing conditional types
     binder: ConditionalTypeBinder
     # Helper for type checking expressions
-    expr_checker: mypy.checkexpr.ExpressionChecker
+    _expr_checker: mypy.checkexpr.ExpressionChecker
 
     pattern_checker: PatternChecker
 
@@ -417,14 +411,18 @@ def __init__(
         self.allow_abstract_call = False
 
         # Child checker objects for specific AST node types
-        self.expr_checker = mypy.checkexpr.ExpressionChecker(
+        self._expr_checker = mypy.checkexpr.ExpressionChecker(
             self, self.msg, self.plugin, per_line_checking_time_ns
         )
         self.pattern_checker = PatternChecker(self, self.msg, self.plugin, options)
 
+    @property
+    def expr_checker(self) -> mypy.checkexpr.ExpressionChecker:
+        return self._expr_checker
+
     @property
     def type_context(self) -> list[Type | None]:
-        return self.expr_checker.type_context
+        return self._expr_checker.type_context
 
     def reset(self) -> None:
         """Cleanup stale state that might be left over from a typechecking run.
@@ -8572,75 +8570,6 @@ def is_node_static(node: Node | None) -> bool | None:
     return None
 
 
-class CheckerScope:
-    # We keep two stacks combined, to maintain the relative order
-    stack: list[TypeInfo | FuncItem | MypyFile]
-
-    def __init__(self, module: MypyFile) -> None:
-        self.stack = [module]
-
-    def current_function(self) -> FuncItem | None:
-        for e in reversed(self.stack):
-            if isinstance(e, FuncItem):
-                return e
-        return None
-
-    def top_level_function(self) -> FuncItem | None:
-        """Return top-level non-lambda function."""
-        for e in self.stack:
-            if isinstance(e, FuncItem) and not isinstance(e, LambdaExpr):
-                return e
-        return None
-
-    def active_class(self) -> TypeInfo | None:
-        if isinstance(self.stack[-1], TypeInfo):
-            return self.stack[-1]
-        return None
-
-    def enclosing_class(self, func: FuncItem | None = None) -> TypeInfo | None:
-        """Is there a class *directly* enclosing this function?"""
-        func = func or self.current_function()
-        assert func, "This method must be called from inside a function"
-        index = self.stack.index(func)
-        assert index, "CheckerScope stack must always start with a module"
-        enclosing = self.stack[index - 1]
-        if isinstance(enclosing, TypeInfo):
-            return enclosing
-        return None
-
-    def active_self_type(self) -> Instance | TupleType | None:
-        """An instance or tuple type representing the current class.
-
-        This returns None unless we are in class body or in a method.
-        In particular, inside a function nested in method this returns None.
-        """
-        info = self.active_class()
-        if not info and self.current_function():
-            info = self.enclosing_class()
-        if info:
-            return fill_typevars(info)
-        return None
-
-    def current_self_type(self) -> Instance | TupleType | None:
-        """Same as active_self_type() but handle functions nested in methods."""
-        for item in reversed(self.stack):
-            if isinstance(item, TypeInfo):
-                return fill_typevars(item)
-        return None
-
-    @contextmanager
-    def push_function(self, item: FuncItem) -> Iterator[None]:
-        self.stack.append(item)
-        yield
-        self.stack.pop()
-
-    @contextmanager
-    def push_class(self, info: TypeInfo) -> Iterator[None]:
-        self.stack.append(info)
-        yield
-        self.stack.pop()
-
-
 TKey = TypeVar("TKey")
 TValue = TypeVar("TValue")
 
diff --git a/mypy/checker_shared.py b/mypy/checker_shared.py
new file mode 100644
index 000000000000..6c62af50466c
--- /dev/null
+++ b/mypy/checker_shared.py
@@ -0,0 +1,349 @@
+"""Shared definitions used by different parts of type checker."""
+
+from __future__ import annotations
+
+from abc import abstractmethod
+from collections.abc import Iterator, Sequence
+from contextlib import contextmanager
+from typing import NamedTuple, overload
+
+from mypy_extensions import trait
+
+from mypy.errorcodes import ErrorCode
+from mypy.errors import ErrorWatcher
+from mypy.message_registry import ErrorMessage
+from mypy.nodes import (
+    ArgKind,
+    Context,
+    Expression,
+    FuncItem,
+    LambdaExpr,
+    MypyFile,
+    Node,
+    RefExpr,
+    TypeAlias,
+    TypeInfo,
+    Var,
+)
+from mypy.plugin import CheckerPluginInterface, Plugin
+from mypy.types import (
+    CallableType,
+    Instance,
+    LiteralValue,
+    Overloaded,
+    PartialType,
+    TupleType,
+    Type,
+    TypedDictType,
+    TypeType,
+)
+from mypy.typevars import fill_typevars
+
+
+# An object that represents either a precise type or a type with an upper bound;
+# it is important for correct type inference with isinstance.
+class TypeRange(NamedTuple):
+    item: Type
+    is_upper_bound: bool  # False => precise type
+
+
+@trait
+class ExpressionCheckerSharedApi:
+    @abstractmethod
+    def accept(
+        self,
+        node: Expression,
+        type_context: Type | None = None,
+        allow_none_return: bool = False,
+        always_allow_any: bool = False,
+        is_callee: bool = False,
+    ) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def analyze_ref_expr(self, e: RefExpr, lvalue: bool = False) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def module_type(self, node: MypyFile) -> Instance:
+        raise NotImplementedError
+
+    @abstractmethod
+    def check_call(
+        self,
+        callee: Type,
+        args: list[Expression],
+        arg_kinds: list[ArgKind],
+        context: Context,
+        arg_names: Sequence[str | None] | None = None,
+        callable_node: Expression | None = None,
+        callable_name: str | None = None,
+        object_type: Type | None = None,
+        original_type: Type | None = None,
+    ) -> tuple[Type, Type]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def transform_callee_type(
+        self,
+        callable_name: str | None,
+        callee: Type,
+        args: list[Expression],
+        arg_kinds: list[ArgKind],
+        context: Context,
+        arg_names: Sequence[str | None] | None = None,
+        object_type: Type | None = None,
+    ) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def method_fullname(self, object_type: Type, method_name: str) -> str | None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def check_method_call_by_name(
+        self,
+        method: str,
+        base_type: Type,
+        args: list[Expression],
+        arg_kinds: list[ArgKind],
+        context: Context,
+        original_type: Type | None = None,
+    ) -> tuple[Type, Type]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def alias_type_in_runtime_context(
+        self, alias: TypeAlias, *, ctx: Context, alias_definition: bool = False
+    ) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def visit_typeddict_index_expr(
+        self, td_type: TypedDictType, index: Expression, setitem: bool = False
+    ) -> tuple[Type, set[str]]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def typeddict_callable(self, info: TypeInfo) -> CallableType:
+        raise NotImplementedError
+
+    @abstractmethod
+    def infer_literal_expr_type(self, value: LiteralValue, fallback_name: str) -> Type:
+        raise NotImplementedError
+
+
+@trait
+class TypeCheckerSharedApi(CheckerPluginInterface):
+    plugin: Plugin
+    module_refs: set[str]
+    scope: CheckerScope
+    checking_missing_await: bool
+
+    @property
+    @abstractmethod
+    def expr_checker(self) -> ExpressionCheckerSharedApi:
+        raise NotImplementedError
+
+    @abstractmethod
+    def named_type(self, name: str) -> Instance:
+        raise NotImplementedError
+
+    @abstractmethod
+    def lookup_typeinfo(self, fullname: str) -> TypeInfo:
+        raise NotImplementedError
+
+    @abstractmethod
+    def lookup_type(self, node: Expression) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    def handle_cannot_determine_type(self, name: str, context: Context) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def handle_partial_var_type(
+        self, typ: PartialType, is_lvalue: bool, node: Var, context: Context
+    ) -> Type:
+        raise NotImplementedError
+
+    @overload
+    @abstractmethod
+    def check_subtype(
+        self,
+        subtype: Type,
+        supertype: Type,
+        context: Context,
+        msg: str,
+        subtype_label: str | None = None,
+        supertype_label: str | None = None,
+        *,
+        notes: list[str] | None = None,
+        code: ErrorCode | None = None,
+        outer_context: Context | None = None,
+    ) -> bool: ...
+
+    @overload
+    @abstractmethod
+    def check_subtype(
+        self,
+        subtype: Type,
+        supertype: Type,
+        context: Context,
+        msg: ErrorMessage,
+        subtype_label: str | None = None,
+        supertype_label: str | None = None,
+        *,
+        notes: list[str] | None = None,
+        outer_context: Context | None = None,
+    ) -> bool: ...
+
+    # Unfortunately, mypyc doesn't support abstract overloads yet.
+    @abstractmethod
+    def check_subtype(
+        self,
+        subtype: Type,
+        supertype: Type,
+        context: Context,
+        msg: str | ErrorMessage,
+        subtype_label: str | None = None,
+        supertype_label: str | None = None,
+        *,
+        notes: list[str] | None = None,
+        code: ErrorCode | None = None,
+        outer_context: Context | None = None,
+    ) -> bool:
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_final_context(self) -> bool:
+        raise NotImplementedError
+
+    @overload
+    @abstractmethod
+    def conditional_types_with_intersection(
+        self,
+        expr_type: Type,
+        type_ranges: list[TypeRange] | None,
+        ctx: Context,
+        default: None = None,
+    ) -> tuple[Type | None, Type | None]: ...
+
+    @overload
+    @abstractmethod
+    def conditional_types_with_intersection(
+        self, expr_type: Type, type_ranges: list[TypeRange] | None, ctx: Context, default: Type
+    ) -> tuple[Type, Type]: ...
+
+    # Unfortunately, mypyc doesn't support abstract overloads yet.
+    @abstractmethod
+    def conditional_types_with_intersection(
+        self,
+        expr_type: Type,
+        type_ranges: list[TypeRange] | None,
+        ctx: Context,
+        default: Type | None = None,
+    ) -> tuple[Type | None, Type | None]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def check_deprecated(self, node: Node | None, context: Context) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def warn_deprecated(self, node: Node | None, context: Context) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def warn_deprecated_overload_item(
+        self, node: Node | None, context: Context, *, target: Type, selftype: Type | None = None
+    ) -> None:
+        raise NotImplementedError
+
+    @abstractmethod
+    def type_is_iterable(self, type: Type) -> bool:
+        raise NotImplementedError
+
+    @abstractmethod
+    def iterable_item_type(
+        self, it: Instance | CallableType | TypeType | Overloaded, context: Context
+    ) -> Type:
+        raise NotImplementedError
+
+    @abstractmethod
+    @contextmanager
+    def checking_await_set(self) -> Iterator[None]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_precise_awaitable_type(self, typ: Type, local_errors: ErrorWatcher) -> Type | None:
+        raise NotImplementedError
+
+
+class CheckerScope:
+    # We keep two stacks combined, to maintain the relative order
+    stack: list[TypeInfo | FuncItem | MypyFile]
+
+    def __init__(self, module: MypyFile) -> None:
+        self.stack = [module]
+
+    def current_function(self) -> FuncItem | None:
+        for e in reversed(self.stack):
+            if isinstance(e, FuncItem):
+                return e
+        return None
+
+    def top_level_function(self) -> FuncItem | None:
+        """Return top-level non-lambda function."""
+        for e in self.stack:
+            if isinstance(e, FuncItem) and not isinstance(e, LambdaExpr):
+                return e
+        return None
+
+    def active_class(self) -> TypeInfo | None:
+        if isinstance(self.stack[-1], TypeInfo):
+            return self.stack[-1]
+        return None
+
+    def enclosing_class(self, func: FuncItem | None = None) -> TypeInfo | None:
+        """Is there a class *directly* enclosing this function?"""
+        func = func or self.current_function()
+        assert func, "This method must be called from inside a function"
+        index = self.stack.index(func)
+        assert index, "CheckerScope stack must always start with a module"
+        enclosing = self.stack[index - 1]
+        if isinstance(enclosing, TypeInfo):
+            return enclosing
+        return None
+
+    def active_self_type(self) -> Instance | TupleType | None:
+        """An instance or tuple type representing the current class.
+
+        This returns None unless we are in class body or in a method.
+        In particular, inside a function nested in method this returns None.
+        """
+        info = self.active_class()
+        if not info and self.current_function():
+            info = self.enclosing_class()
+        if info:
+            return fill_typevars(info)
+        return None
+
+    def current_self_type(self) -> Instance | TupleType | None:
+        """Same as active_self_type() but handle functions nested in methods."""
+        for item in reversed(self.stack):
+            if isinstance(item, TypeInfo):
+                return fill_typevars(item)
+        return None
+
+    @contextmanager
+    def push_function(self, item: FuncItem) -> Iterator[None]:
+        self.stack.append(item)
+        yield
+        self.stack.pop()
+
+    @contextmanager
+    def push_class(self, info: TypeInfo) -> Iterator[None]:
+        self.stack.append(info)
+        yield
+        self.stack.pop()
diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index 12480cf9ab93..099e151dd33d 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -15,6 +15,7 @@
 import mypy.errorcodes as codes
 from mypy import applytype, erasetype, join, message_registry, nodes, operators, types
 from mypy.argmap import ArgTypeExpander, map_actuals_to_formals, map_formals_to_actuals
+from mypy.checker_shared import ExpressionCheckerSharedApi
 from mypy.checkmember import analyze_member_access
 from mypy.checkstrformat import StringFormatterChecker
 from mypy.erasetype import erase_type, remove_instance_last_known_values, replace_meta_vars
@@ -296,7 +297,7 @@ class UseReverse(enum.Enum):
 USE_REVERSE_NEVER: Final = UseReverse.NEVER
 
 
-class ExpressionChecker(ExpressionVisitor[Type]):
+class ExpressionChecker(ExpressionVisitor[Type], ExpressionCheckerSharedApi):
     """Expression type checker.
 
     This class works closely together with checker.TypeChecker.
@@ -338,7 +339,7 @@ def __init__(
         # TODO: refactor this to use a pattern similar to one in
         # multiassign_from_union, or maybe even combine the two?
         self.type_overrides: dict[Expression, Type] = {}
-        self.strfrm_checker = StringFormatterChecker(self, self.chk, self.msg)
+        self.strfrm_checker = StringFormatterChecker(self.chk, self.msg)
 
         self.resolved_type = {}
 
diff --git a/mypy/checkmember.py b/mypy/checkmember.py
index dfb141aa415c..2152e309b1df 100644
--- a/mypy/checkmember.py
+++ b/mypy/checkmember.py
@@ -3,9 +3,10 @@
 from __future__ import annotations
 
 from collections.abc import Sequence
-from typing import TYPE_CHECKING, Callable, cast
+from typing import Callable, cast
 
-from mypy import message_registry, subtypes
+from mypy import message_registry, state, subtypes
+from mypy.checker_shared import TypeCheckerSharedApi
 from mypy.erasetype import erase_typevars
 from mypy.expandtype import (
     expand_self_type,
@@ -73,11 +74,6 @@
     get_proper_type,
 )
 
-if TYPE_CHECKING:  # import for forward declaration only
-    import mypy.checker
-
-from mypy import state
-
 
 class MemberContext:
     """Information and objects needed to type check attribute access.
@@ -93,7 +89,7 @@ def __init__(
         is_operator: bool,
         original_type: Type,
         context: Context,
-        chk: mypy.checker.TypeChecker,
+        chk: TypeCheckerSharedApi,
         self_type: Type | None = None,
         module_symbol_table: SymbolTable | None = None,
         no_deferral: bool = False,
@@ -165,7 +161,7 @@ def analyze_member_access(
     is_super: bool,
     is_operator: bool,
     original_type: Type,
-    chk: mypy.checker.TypeChecker,
+    chk: TypeCheckerSharedApi,
     override_info: TypeInfo | None = None,
     in_literal_context: bool = False,
     self_type: Type | None = None,
diff --git a/mypy/checkpattern.py b/mypy/checkpattern.py
index c71d83324694..4cf7c1ca7862 100644
--- a/mypy/checkpattern.py
+++ b/mypy/checkpattern.py
@@ -5,8 +5,8 @@
 from collections import defaultdict
 from typing import Final, NamedTuple
 
-import mypy.checker
 from mypy import message_registry
+from mypy.checker_shared import TypeCheckerSharedApi, TypeRange
 from mypy.checkmember import analyze_member_access
 from mypy.expandtype import expand_type_by_instance
 from mypy.join import join_types
@@ -91,7 +91,7 @@ class PatternChecker(PatternVisitor[PatternType]):
     """
 
     # Some services are provided by a TypeChecker instance.
-    chk: mypy.checker.TypeChecker
+    chk: TypeCheckerSharedApi
     # This is shared with TypeChecker, but stored also here for convenience.
     msg: MessageBuilder
     # Currently unused
@@ -112,7 +112,7 @@ class PatternChecker(PatternVisitor[PatternType]):
     options: Options
 
     def __init__(
-        self, chk: mypy.checker.TypeChecker, msg: MessageBuilder, plugin: Plugin, options: Options
+        self, chk: TypeCheckerSharedApi, msg: MessageBuilder, plugin: Plugin, options: Options
     ) -> None:
         self.chk = chk
         self.msg = msg
@@ -802,7 +802,7 @@ def get_var(expr: Expression) -> Var:
     return node
 
 
-def get_type_range(typ: Type) -> mypy.checker.TypeRange:
+def get_type_range(typ: Type) -> TypeRange:
     typ = get_proper_type(typ)
     if (
         isinstance(typ, Instance)
@@ -810,7 +810,7 @@ def get_type_range(typ: Type) -> mypy.checker.TypeRange:
         and isinstance(typ.last_known_value.value, bool)
     ):
         typ = typ.last_known_value
-    return mypy.checker.TypeRange(typ, is_upper_bound=False)
+    return TypeRange(typ, is_upper_bound=False)
 
 
 def is_uninhabited(typ: Type) -> bool:
diff --git a/mypy/checkstrformat.py b/mypy/checkstrformat.py
index 289961523b1d..45075bd37552 100644
--- a/mypy/checkstrformat.py
+++ b/mypy/checkstrformat.py
@@ -14,11 +14,15 @@
 
 import re
 from re import Match, Pattern
-from typing import TYPE_CHECKING, Callable, Final, Union, cast
+from typing import Callable, Final, Union, cast
 from typing_extensions import TypeAlias as _TypeAlias
 
 import mypy.errorcodes as codes
+from mypy import message_registry
+from mypy.checker_shared import TypeCheckerSharedApi
 from mypy.errors import Errors
+from mypy.maptype import map_instance_to_supertype
+from mypy.messages import MessageBuilder
 from mypy.nodes import (
     ARG_NAMED,
     ARG_POS,
@@ -41,6 +45,9 @@
     TempNode,
     TupleExpr,
 )
+from mypy.parse import parse
+from mypy.subtypes import is_subtype
+from mypy.typeops import custom_special_method
 from mypy.types import (
     AnyType,
     Instance,
@@ -57,18 +64,6 @@
     get_proper_types,
 )
 
-if TYPE_CHECKING:
-    # break import cycle only needed for mypy
-    import mypy.checker
-    import mypy.checkexpr
-
-from mypy import message_registry
-from mypy.maptype import map_instance_to_supertype
-from mypy.messages import MessageBuilder
-from mypy.parse import parse
-from mypy.subtypes import is_subtype
-from mypy.typeops import custom_special_method
-
 FormatStringExpr: _TypeAlias = Union[StrExpr, BytesExpr]
 Checkers: _TypeAlias = tuple[Callable[[Expression], None], Callable[[Type], bool]]
 MatchMap: _TypeAlias = dict[tuple[int, int], Match[str]]  # span -> match
@@ -299,21 +294,13 @@ class StringFormatterChecker:
     """
 
     # Some services are provided by a TypeChecker instance.
-    chk: mypy.checker.TypeChecker
+    chk: TypeCheckerSharedApi
     # This is shared with TypeChecker, but stored also here for convenience.
     msg: MessageBuilder
-    # Some services are provided by a ExpressionChecker instance.
-    exprchk: mypy.checkexpr.ExpressionChecker
 
-    def __init__(
-        self,
-        exprchk: mypy.checkexpr.ExpressionChecker,
-        chk: mypy.checker.TypeChecker,
-        msg: MessageBuilder,
-    ) -> None:
+    def __init__(self, chk: TypeCheckerSharedApi, msg: MessageBuilder) -> None:
         """Construct an expression type checker."""
         self.chk = chk
-        self.exprchk = exprchk
         self.msg = msg
 
     def check_str_format_call(self, call: CallExpr, format_value: str) -> None:
@@ -618,7 +605,7 @@ def apply_field_accessors(
         # TODO: fix column to point to actual start of the format specifier _within_ string.
         temp_ast.line = ctx.line
         temp_ast.column = ctx.column
-        self.exprchk.accept(temp_ast)
+        self.chk.expr_checker.accept(temp_ast)
         return temp_ast
 
     def validate_and_transform_accessors(
@@ -685,7 +672,7 @@ def check_str_interpolation(self, expr: FormatStringExpr, replacements: Expressi
         """Check the types of the 'replacements' in a string interpolation
         expression: str % replacements.
         """
-        self.exprchk.accept(expr)
+        self.chk.expr_checker.accept(expr)
         specifiers = parse_conversion_specifiers(expr.value)
         has_mapping_keys = self.analyze_conversion_specifiers(specifiers, expr)
         if has_mapping_keys is None: