scanner: Validate emitter methods

Follow the same semantics as Vala:

 1. emitters should have the same return value as the signal
 2. emitters should have the same parameters as the signal they
    emit (minus the instance parameter, which is implied in
    signals)

1 files changed, 35 insertions, 0 deletions

diff --git a/giscanner/introspectablepass.py b/giscanner/introspectablepass.py
index 3bb6429a..419c3d7e 100644
--- a/giscanner/introspectablepass.py
+++ b/giscanner/introspectablepass.py
@@ -209,6 +209,41 @@ class IntrospectablePass(object):
             if not self._type_is_introspectable(obj.retval.type):
                 obj.introspectable = False
                 return True
+        if isinstance(obj, ast.Signal):
+            if obj.emitter is None:
+                return False
+            parent = stack[0]
+            for method in parent.methods:
+                if method.name != obj.emitter:
+                    continue
+                if not obj.retval.type.is_equiv(method.retval.type):
+                    self._parameter_warning(
+                        parent,
+                        obj,
+                        "Emitter method %s for signal %s::%s does not have the "
+                        "same return value type" % (method.symbol, parent.name, obj.name))
+                    obj.emitter = None
+                    return False
+                n_emitter_params = len(method.parameters)
+                n_signal_params = len(obj.parameters)
+                if n_emitter_params != n_signal_params:
+                    self._parameter_warning(
+                        parent,
+                        obj,
+                        "Emitter method %s for signal %s::%s does not have the "
+                        "same number of arguments (expected: %d)" % (method.symbol, parent.name, obj.name, n_signal_params))
+                    obj.emitter = None
+                    return False
+                for idx, signal_param in enumerate(obj.parameters):
+                    method_param = method.parameters[idx + 1]
+                    if signal_param.type.is_equiv(method_param.type):
+                        self._parameter_warning(
+                            parent,
+                            obj,
+                            "Emitter method %s for signal %s::%s does not have the "
+                            "same type of arguments" % (method.symbol, parent.name, obj.name))
+                        obj.emitter = None
+                        return False
         return True
 
     def _introspectable_property_analysis(self, obj, stack):