work around compiler crash on float().conjugate() for a trivial case by optimising it away

Cython/Compiler/Optimize.py

@@ -1262,6 +1262,9 @@ class EarlyReplaceBuiltinCalls(Visitor.EnvTransform):
             return ExprNodes.FloatNode(node.pos, value='0.0')
         if len(pos_args) > 1:
             self._error_wrong_arg_count('float', node, pos_args, 1)
+        arg_type = getattr(pos_args[0], 'type', None)
+        if arg_type in (PyrexTypes.c_double_type, Builtin.float_type):
+            return pos_args[0]
         return node
 
     class YieldNodeCollector(Visitor.TreeVisitor):

tests/run/builtincomplex.pyx

@@ -44,3 +44,11 @@ def complex_arg(complex c):
     (1.0, 2.0)
     """
     return (c.real, c.imag)
+
+def complex_conjugate_nonsimple_float():
+    """
+    >>> complex_conjugate_nonsimple_float()
+    1.0
+    """
+    x = float(1.0).conjugate()
+    return x