do not try to generated embedded signatures for lambda functions

Cython/Compiler/AutoDocTransforms.py

@@ -150,6 +150,10 @@ class EmbedSignature(CythonTransform):
         self.class_node = oldclass
         return node
 
+    def visit_LambdaNode(self, node):
+        # lambda expressions so not have signature or inner functions
+        return node
+
     def visit_DefNode(self, node):
         if not self.current_directives['embedsignature']:
             return node

tests/run/embedsignatures.pyx

@@ -402,3 +402,7 @@ cpdef f_defexpr4(int x = (Ext.CONST1 + FLAG1) * Ext.CONST2):
 
 cpdef f_defexpr5(int x = 2+2):
     pass
+
+# no signatures for lambda functions
+lambda_foo = lambda x: 10
+lambda_bar = lambda x: 20