interpreter: Introduce operators support for InterpreterObjects

5 files changed, 202 insertions, 5 deletions

diff --git a/mesonbuild/interpreterbase/__init__.py b/mesonbuild/interpreterbase/__init__.py
index f7b12a5..c3605b2 100644
--- a/mesonbuild/interpreterbase/__init__.py
+++ b/mesonbuild/interpreterbase/__init__.py
@@ -20,6 +20,8 @@ __all__ = [
     'MesonVersionString',
     'MutableInterpreterObject',
 
+    'MesonOperator',
+
     'Disabler',
     'is_disabled',
 
@@ -43,6 +45,8 @@ __all__ = [
     'permissive_unholder_return',
     'disablerIfNotFound',
     'permittedKwargs',
+    'typed_operator',
+    'unary_operator',
     'typed_pos_args',
     'ContainerTypeInfo',
     'KwargInfo',
diff --git a/mesonbuild/interpreterbase/baseobjects.py b/mesonbuild/interpreterbase/baseobjects.py
index ddfd4be..b28654a 100644
--- a/mesonbuild/interpreterbase/baseobjects.py
+++ b/mesonbuild/interpreterbase/baseobjects.py
@@ -13,9 +13,11 @@
 # limitations under the License.
 
 from .. import mparser
-from .exceptions import InvalidCode
+from .exceptions import InvalidCode, InvalidArguments
 from .helpers import flatten, resolve_second_level_holders
-from ..mesonlib import HoldableObject
+from .operator import MesonOperator
+from ..mesonlib import HoldableObject, MesonBugException
+import textwrap
 
 import typing as T
 
@@ -36,17 +38,41 @@ TYPE_kwargs = T.Dict[str, TYPE_var]
 TYPE_nkwargs = T.Dict[str, TYPE_nvar]
 TYPE_key_resolver = T.Callable[[mparser.BaseNode], str]
 
+if T.TYPE_CHECKING:
+    from typing_extensions import Protocol
+    __T = T.TypeVar('__T', bound=TYPE_var, contravariant=True)
+    class OperatorCall(Protocol[__T]):
+        def __call__(self, other: __T) -> TYPE_var: ...
+
 class InterpreterObject:
     def __init__(self, *, subproject: T.Optional[str] = None) -> None:
         self.methods: T.Dict[
             str,
             T.Callable[[T.List[TYPE_var], TYPE_kwargs], TYPE_var]
         ] = {}
+        self.operators: T.Dict[MesonOperator, 'OperatorCall'] = {}
+        self.trivial_operators: T.Dict[
+            MesonOperator,
+            T.Tuple[
+                T.Type[T.Union[TYPE_var, T.Tuple[TYPE_var, ...]]],
+                'OperatorCall'
+            ]
+        ] = {}
         # Current node set during a method call. This can be used as location
         # when printing a warning message during a method call.
         self.current_node:  mparser.BaseNode = None
         self.subproject: str = subproject or ''
 
+        # Some default operators supported by all objects
+        self.operators.update({
+            MesonOperator.EQUALS: self.op_equals,
+            MesonOperator.NOT_EQUALS: self.op_not_equals,
+        })
+
+    # The type of the object that can be printed to the user
+    def display_name(self) -> str:
+        return type(self).__name__
+
     def method_call(
                 self,
                 method_name: str,
@@ -62,13 +88,47 @@ class InterpreterObject:
             return method(args, kwargs)
         raise InvalidCode(f'Unknown method "{method_name}" in object {self} of type {type(self).__name__}.')
 
+    def operator_call(self, operator: MesonOperator, other: TYPE_var) -> TYPE_var:
+        if operator in self.trivial_operators:
+            op = self.trivial_operators[operator]
+            if op[0] is None and other is not None:
+                raise MesonBugException(f'The unary operator `{operator.value}` of {self.display_name()} was passed the object {other} of type {type(other).__name__}')
+            if op[0] is not None and not isinstance(other, op[0]):
+                raise InvalidArguments(f'The `{operator.value}` of {self.display_name()} does not accept objects of type {type(other).__name__} ({other})')
+            return op[1](other)
+        if operator in self.operators:
+            return self.operators[operator](other)
+        raise InvalidCode(f'Object {self} of type {self.display_name()} does not support the `{operator.value}` operator.')
+
+
+    # Default comparison operator support
+    def _throw_comp_exception(self, other: TYPE_var, opt_type: str) -> T.NoReturn:
+        raise InvalidArguments(textwrap.dedent(
+            f'''
+                Trying to compare values of different types ({self.display_name()}, {type(other).__name__}) using {opt_type}.
+                This was deprecated and undefined behavior previously and is as of 0.60.0 a hard error.
+            '''
+        ))
+
+    def op_equals(self, other: TYPE_var) -> bool:
+        if type(self) != type(other):
+            self._throw_comp_exception(other, '==')
+        return self == other
+
+    def op_not_equals(self, other: TYPE_var) -> bool:
+        if type(self) != type(other):
+            self._throw_comp_exception(other, '!=')
+        return self != other
+
 class MesonInterpreterObject(InterpreterObject):
     ''' All non-elementary objects and non-object-holders should be derived from this '''
 
 class MutableInterpreterObject:
     ''' Dummy class to mark the object type as mutable '''
 
-InterpreterObjectTypeVar = T.TypeVar('InterpreterObjectTypeVar', bound=HoldableObject)
+HoldableTypes = (HoldableObject, int)
+TYPE_HoldableTypes = T.Union[HoldableObject, int]
+InterpreterObjectTypeVar = T.TypeVar('InterpreterObjectTypeVar', bound=TYPE_HoldableTypes)
 
 class ObjectHolder(InterpreterObject, T.Generic[InterpreterObjectTypeVar]):
     def __init__(self, obj: InterpreterObjectTypeVar, interpreter: 'Interpreter') -> None:
@@ -77,11 +137,26 @@ class ObjectHolder(InterpreterObject, T.Generic[InterpreterObjectTypeVar]):
         # HoldableObject, not the specialized type, so only do this assert in
         # non-type checking situations
         if not T.TYPE_CHECKING:
-            assert isinstance(obj, HoldableObject), f'This is a bug: Trying to hold object of type `{type(obj).__name__}` that is not an `HoldableObject`'
+            assert isinstance(obj, HoldableTypes), f'This is a bug: Trying to hold object of type `{type(obj).__name__}` that is not in `{HoldableTypes}`'
         self.held_object = obj
         self.interpreter = interpreter
         self.env = self.interpreter.environment
 
+    # Hide the object holder abstrction from the user
+    def display_name(self) -> str:
+        return type(self.held_object).__name__
+
+    # Override default comparison operators for the held object
+    def op_equals(self, other: TYPE_var) -> bool:
+        if type(self.held_object) != type(other):
+            self._throw_comp_exception(other, '==')
+        return self.held_object == other
+
+    def op_not_equals(self, other: TYPE_var) -> bool:
+        if type(self.held_object) != type(other):
+            self._throw_comp_exception(other, '!=')
+        return self.held_object != other
+
     def __repr__(self) -> str:
         return f'<[{type(self).__name__}] holds [{type(self.held_object).__name__}]: {self.held_object!r}>'
 
diff --git a/mesonbuild/interpreterbase/decorators.py b/mesonbuild/interpreterbase/decorators.py
index 33892be..717853f 100644
--- a/mesonbuild/interpreterbase/decorators.py
+++ b/mesonbuild/interpreterbase/decorators.py
@@ -17,6 +17,7 @@ from .baseobjects import TV_func, TYPE_var, TYPE_kwargs
 from .disabler import Disabler
 from .exceptions import InterpreterException, InvalidArguments
 from .helpers import check_stringlist
+from .operator import MesonOperator
 from ._unholder import _unholder
 
 from functools import wraps
@@ -110,6 +111,49 @@ class permittedKwargs:
             return f(*wrapped_args, **wrapped_kwargs)
         return T.cast(TV_func, wrapped)
 
+if T.TYPE_CHECKING:
+    from .baseobjects import InterpreterObject
+    from typing_extensions import Protocol
+
+    _TV_IntegerObject = T.TypeVar('_TV_IntegerObject', bound=InterpreterObject, contravariant=True)
+    _TV_ARG1 = T.TypeVar('_TV_ARG1', bound=TYPE_var, contravariant=True)
+
+    class FN_Operator(Protocol[_TV_IntegerObject, _TV_ARG1]):
+        def __call__(s, self: _TV_IntegerObject, other: _TV_ARG1) -> TYPE_var: ...
+    _TV_FN_Operator = T.TypeVar('_TV_FN_Operator', bound=FN_Operator)
+
+def typed_operator(operator: MesonOperator,
+                   types: T.Union[T.Type, T.Tuple[T.Type, ...]]) -> T.Callable[['_TV_FN_Operator'], '_TV_FN_Operator']:
+    """Decorator that does type checking for operator calls.
+
+    The principle here is similar to typed_pos_args, however much simpler
+    since only one other object ever is passed
+    """
+    def inner(f: '_TV_FN_Operator') -> '_TV_FN_Operator':
+        @wraps(f)
+        def wrapper(self: 'InterpreterObject', other: TYPE_var) -> TYPE_var:
+            if not isinstance(other, types):
+                raise InvalidArguments(f'The `{operator.value}` of {self.display_name()} does not accept objects of type {type(other).__name__} ({other})')
+            return f(self, other)
+        return T.cast('_TV_FN_Operator', wrapper)
+    return inner
+
+def unary_operator(operator: MesonOperator) -> T.Callable[['_TV_FN_Operator'], '_TV_FN_Operator']:
+    """Decorator that does type checking for operator calls.
+
+    This decorator is for unary operators that do not take any other objects.
+    It should be impossible for a user to accidentally break this. Triggering
+    this check always indicates a bug in the Meson interpreter.
+    """
+    def inner(f: '_TV_FN_Operator') -> '_TV_FN_Operator':
+        @wraps(f)
+        def wrapper(self: 'InterpreterObject', other: TYPE_var) -> TYPE_var:
+            if other is not None:
+                raise mesonlib.MesonBugException(f'The unary operator `{operator.value}` of {self.display_name()} was passed the object {other} of type {type(other).__name__}')
+            return f(self, other)
+        return T.cast('_TV_FN_Operator', wrapper)
+    return inner
+
 
 def typed_pos_args(name: str, *types: T.Union[T.Type, T.Tuple[T.Type, ...]],
                    varargs: T.Optional[T.Union[T.Type, T.Tuple[T.Type, ...]]] = None,
diff --git a/mesonbuild/interpreterbase/interpreterbase.py b/mesonbuild/interpreterbase/interpreterbase.py
index 289e1d7..b6e7d0d 100644
--- a/mesonbuild/interpreterbase/interpreterbase.py
+++ b/mesonbuild/interpreterbase/interpreterbase.py
@@ -43,6 +43,7 @@ from .exceptions import (
 from .decorators import FeatureNew, noKwargs
 from .disabler import Disabler, is_disabled
 from .helpers import check_stringlist, default_resolve_key, flatten, resolve_second_level_holders
+from .operator import MesonOperator
 from ._unholder import _unholder
 
 import os, copy, re, pathlib
@@ -290,13 +291,37 @@ class InterpreterBase:
             raise InvalidArguments('rvalue of "in" operator must be an array or a dict')
         return val1 in val2
 
-    def evaluate_comparison(self, node: mparser.ComparisonNode) -> T.Union[bool, Disabler]:
+    def evaluate_comparison(self, node: mparser.ComparisonNode) -> T.Union[TYPE_var, InterpreterObject]:
         val1 = self.evaluate_statement(node.left)
         if isinstance(val1, Disabler):
             return val1
         val2 = self.evaluate_statement(node.right)
         if isinstance(val2, Disabler):
             return val2
+
+        # New code based on InterpreterObjects
+        operator = {
+            'in': MesonOperator.IN,
+            'notin': MesonOperator.NOT_IN,
+            '==': MesonOperator.EQUALS,
+            '!=': MesonOperator.NOT_EQUALS,
+            '>': MesonOperator.GREATER,
+            '<': MesonOperator.LESS,
+            '>=': MesonOperator.GREATER_EQUALS,
+            '<=': MesonOperator.LESS_EQUALS,
+        }[node.ctype]
+
+        # Check if the arguments should be reversed for simplicity (this essentially converts `in` to `contains`)
+        if operator in (MesonOperator.IN, MesonOperator.NOT_IN) and isinstance(val2, InterpreterObject):
+            return self._holderify(val2.operator_call(operator, _unholder(val1)))
+
+        # Normal evaluation, with the same semantics
+        elif operator not in (MesonOperator.IN, MesonOperator.NOT_IN) and isinstance(val1, InterpreterObject):
+            return self._holderify(val1.operator_call(operator, _unholder(val2)))
+
+        # OLD CODE, based on the builtin types -- remove once we have switched
+        # over to all ObjectHolders.
+
         # Do not compare the ObjectHolders but the actual held objects
         val1 = _unholder(val1)
         val2 = _unholder(val2)
@@ -404,6 +429,21 @@ class InterpreterBase:
         if isinstance(r, Disabler):
             return r
 
+        # New code based on InterpreterObjects
+        if isinstance(l, InterpreterObject):
+            mapping: T.Dict[str, MesonOperator] = {
+                'add': MesonOperator.PLUS,
+                'sub': MesonOperator.MINUS,
+                'mul': MesonOperator.TIMES,
+                'div': MesonOperator.DIV,
+                'mod': MesonOperator.MOD,
+            }
+            res = l.operator_call(mapping[cur.operation], _unholder(r))
+            return self._holderify(res)
+
+        # OLD CODE, based on the builtin types -- remove once we have switched
+        # over to all ObjectHolders.
+
         if cur.operation == 'add':
             if isinstance(l, dict) and isinstance(r, dict):
                 return {**l, **r}
diff --git a/mesonbuild/interpreterbase/operator.py b/mesonbuild/interpreterbase/operator.py
new file mode 100644
index 0000000..bf9b6b0
--- /dev/null
+++ b/mesonbuild/interpreterbase/operator.py
@@ -0,0 +1,34 @@
+# SPDX-license-identifier: Apache-2.0
+
+from enum import Enum
+
+class MesonOperator(Enum):
+    # Arithmetic
+    PLUS = '+'
+    MINUS = '-'
+    TIMES = '*'
+    DIV = '/'
+    MOD = '%'
+
+    UMINUS = 'uminus'
+
+    # Logic
+    NOT = 'not'
+    AND = 'and'
+    OR = 'or'
+
+    # Should return the boolsche interpretation of the value (`'' == false` for instance)
+    BOOL = 'bool()'
+
+    # Comparision
+    EQUALS = '=='
+    NOT_EQUALS = '!='
+    GREATER = '>'
+    LESS = '<'
+    GREATER_EQUALS = '>='
+    LESS_EQUALS = '<='
+
+    # Container
+    IN = 'in'
+    NOT_IN = 'not in'
+    INDEX = '[]'