add some operator tests for precedences (array indexing)

test/completion/operators.py

@@ -0,0 +1,25 @@
+"""
+Test Jedi's operation understanding. Jedi should understand simple additions,
+multiplications, etc.
+"""
+x = [1, 'a', 1.0]
+
+#? int() str() float()
+x[12]
+
+#? str()
+x[1 + 1]
+
+index = 0 + 2
+
+#? float()
+x[index]
+
+
+def calculate(number):
+    return number + constant
+
+constant = 1
+
+#? float()
+x[calculate(2)]