Handle hex bigint literals in nativeparse

Author: ilevkivskyi

mypy/nativeparse.py

@@ -1582,7 +1582,7 @@ def read_expression(state: State, data: ReadBuffer) -> Expression:
         return expr
     elif tag == nodes.BIG_INT_EXPR:
         strval = read_str(data)
-        ie = IntExpr(int(strval))
+        ie = IntExpr(int(strval, base=0))
         read_loc(data, ie)
         expect_end_tag(data)
         return ie

test-data/unit/native-parser.test

@@ -40,7 +40,7 @@ MypyFile:1(
       StrExpr(z))))
 
 [case testIntExpr]
-(0, 1, 2, 203, 5345, 50123, 1234567890, 9982374892739487239847897928374897298374)
+(0, 1, 2, 203, 5345, 50123, 1234567890, 9982374892739487239847897928374897298374, 0x1950A86A20F9469CFC6C)
 [out]
 MypyFile:1(
   ExpressionStmt:1(
@@ -52,7 +52,8 @@ MypyFile:1(
       IntExpr(5345)
       IntExpr(50123)
       IntExpr(1234567890)
-      IntExpr(9982374892739487239847897928374897298374))))
+      IntExpr(9982374892739487239847897928374897298374)
+      IntExpr(119547037146038801333356))))
 
 [case testAssignmentStmt]
 x = 1