Added generalized signature matching

This is necessary to properly support callback protocols.

Note that the implementation does not currently support typing.ParamSpec.
This will be added in a follow up.

PiperOrigin-RevId: 827866351

Author: superbobry

pytype/matcher.py

@@ -947,6 +947,143 @@ def _match_type_against_type(self, left, other_type, subst, view):
           % (type(left), type(other_type))
       )
 
+  def _match_signatures(self, sig, other_sig, subst, view):
+    """Checks if signature `sig` is compatible with signature `other_sig`."""
+    # Track unconsumed required parameters in sig that could accept keyword
+    # arguments (i.e., non-positional-only parameters without defaults).
+    unconsumed_kw_params = {
+        *sig.param_names[sig.posonly_count :],
+        *sig.kwonly_params,
+    } - sig.defaults.keys()
+
+    new_substs = []
+
+    # Track the index in sig.param_names as we consume positional parameters.
+    sig_pos_index = 0
+
+    # For normal (positional-or-keyword) parameters in other_sig, sig must be
+    # prepared to receive these as either positional or keyword arguments.
+    for other_param_idx, other_param in enumerate(other_sig.param_names):
+      other_type = other_sig.annotations.get(
+          other_param, self.ctx.convert.unsolvable
+      )
+      # Check if this is a normal parameter (not positional-only) in other_sig.
+      other_is_normal = other_param_idx >= other_sig.posonly_count
+
+      # Check that there is a corresponding positional parameter in sig.
+      # Note that the name does not have to agree.
+      if sig_pos_index < len(sig.param_names):
+        sig_param = sig.param_names[sig_pos_index]
+        other_is_optional = other_param in other_sig.defaults
+        sig_is_required = sig_param not in sig.defaults
+        if other_is_optional and sig_is_required:
+          return None
+        sig_type = sig.annotations.get(sig_param, self.ctx.convert.unsolvable)
+        sig_pos_index += 1
+        unconsumed_kw_params.discard(sig_param)
+      elif sig.varargs_name:
+        varargs_type = sig.annotations.get(
+            sig.varargs_name, self.ctx.convert.unsolvable
+        )
+        sig_type = self.ctx.convert.get_element_type(varargs_type)
+        if sig_type is None:
+          sig_type = self.ctx.convert.unsolvable
+      else:
+        return None
+      new_subst = self._instantiate_and_match(other_type, sig_type, subst, view)
+      if new_subst is None:
+        return None
+      new_substs.append(new_subst)
+
+      # Normal parameters can also be passed by keyword, so check that there
+      # is a corresponding keyword parameter in sig.
+      if other_is_normal:
+        # Check if sig can accept this parameter by keyword
+        if other_param in sig.kwonly_params or other_param in sig.param_names:
+          if other_param in sig.param_names:
+            kw_param_idx = sig.param_names.index(other_param)
+          else:
+            kw_param_idx = len(sig.param_names) + sig.kwonly_params.index(
+                other_param
+            )
+
+          # Check if it's the same parameter we just matched positionally
+          pos_param_idx = sig_pos_index - 1 if sig_pos_index > 0 else -1
+          if pos_param_idx >= 0 and pos_param_idx < len(sig.param_names):
+            if kw_param_idx != pos_param_idx:
+              # This has to be either the same parameter as the positional one
+              # (i.e. they are at the same index in sig), or they both have to
+              # be optional (because only one can be passed).
+              pos_param = sig.param_names[pos_param_idx]
+              if (
+                  pos_param not in sig.defaults
+                  or other_param not in sig.defaults
+              ):
+                return None
+              # Also check type compatibility for the keyword parameter
+              kw_type = sig.annotations.get(
+                  other_param, self.ctx.convert.unsolvable
+              )
+              new_subst = self._instantiate_and_match(
+                  other_type, kw_type, subst, view
+              )
+              if new_subst is None:
+                return None
+          elif pos_param_idx == -1:
+            # Matched via varargs - no additional check needed
+            pass
+        elif not sig.kwargs_name:
+          # sig has no **kwargs to accept this keyword argument
+          return None
+
+    # sig cannot have unconsumed positional-only required parameters.
+    for i in range(sig_pos_index, sig.posonly_count):
+      if sig.param_names[i] not in sig.defaults:
+        return None
+
+    # Match other_sig's keyword-only parameters against sig.
+    for kwonly_param in other_sig.kwonly_params:
+      other_type = other_sig.annotations.get(
+          kwonly_param, self.ctx.convert.unsolvable
+      )
+      if kwonly_param in sig.kwonly_params or kwonly_param in sig.param_names:
+        other_is_optional = kwonly_param in other_sig.defaults
+        sig_is_required = kwonly_param not in sig.defaults
+        if other_is_optional and sig_is_required:
+          return None
+        sig_type = sig.annotations.get(
+            kwonly_param, self.ctx.convert.unsolvable
+        )
+        unconsumed_kw_params.discard(kwonly_param)
+      elif sig.kwargs_name:
+        kwargs_type = sig.annotations.get(
+            sig.kwargs_name, self.ctx.convert.unsolvable
+        )
+        sig_type = self.ctx.convert.get_element_type(kwargs_type)
+        if sig_type is None:
+          sig_type = self.ctx.convert.unsolvable
+      else:
+        return None
+      new_subst = self._instantiate_and_match(other_type, sig_type, subst, view)
+      if new_subst is None:
+        return None
+      new_substs.append(new_subst)
+
+    # sig cannot have unconsumed required parameters (those not covered by
+    # *args or **kwargs).
+    if not sig.varargs_name and not sig.kwargs_name:
+      if unconsumed_kw_params:
+        return None
+
+    sig_ret = sig.annotations.get("return", self.ctx.convert.unsolvable)
+    other_ret = other_sig.annotations.get("return", self.ctx.convert.unsolvable)
+    new_subst = self._instantiate_and_match(sig_ret, other_ret, subst, view)
+    if new_subst is None:
+      return None
+    new_substs.append(new_subst)
+
+    return self._merge_substs(subst, new_substs)
+
   def _match_type_against_callback_protocol(
       self, left, other_type, subst, view
   ):
@@ -961,17 +1098,20 @@ def _match_type_against_callback_protocol(
     ):
       return None
     new_substs = []
+    left_signatures = self._get_signatures(left, subst, view)
     for expected_method in method_var.data:
       signatures = function.get_signatures(expected_method)
       for sig in signatures:
         sig = sig.drop_first_parameter()  # drop `self`
-        expected_callable = self.ctx.pytd_convert.signature_to_callable(sig)
-        new_subst = self._match_type_against_type(
-            left, expected_callable, subst, view
-        )
-        if new_subst is not None:
-          # For a set of overloaded signatures, only one needs to match.
-          new_substs.append(new_subst)
+        found = False
+        for left_sig in left_signatures:
+          new_subst = self._match_signatures(left_sig, sig, subst, view)
+          if new_subst is not None:
+            # For a set of overloaded signatures, only one needs to match.
+            found = True
+            new_substs.append(new_subst)
+            break
+        if found:
           break
       else:
         # Every method_var binding must have a matching signature.

pytype/tests/CMakeLists.txt

@@ -242,6 +242,15 @@ py_test(
     .test_base
 )
 
+py_test(
+  NAME
+    test_signatures
+  SRCS
+    test_signatures.py
+  DEPS
+    .test_base
+)
+
 py_test(
   NAME
     test_slice1

pytype/tests/test_protocols2.py

@@ -676,6 +676,28 @@ def f3(x: int) -> str:
           pythonpath=[d.path],
       )
 
+  def test_callback_protocol_kw_only(self):
+    self.CheckWithErrors("""
+      from typing import Protocol
+      class Foo(Protocol):
+        def __call__(self, *, x: str) -> str:
+          return x
+
+      def f1() -> str:
+        return ''
+      def f2(x: str) -> str:
+        return ''
+      def f3(x: int) -> str:
+        return str(x)
+
+      def accepts_foo(f: Foo):
+        pass
+
+      accepts_foo(f1)  # wrong-arg-types
+      accepts_foo(f2)
+      accepts_foo(f3)  # wrong-arg-types
+    """)
+
   def test_class_matches_callback_protocol(self):
     self.CheckWithErrors("""
       from typing_extensions import Protocol