[GROOVY-7468] type checker should use superclass bound when expected by generics

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.3
• Fix Version/s: 4.0.0-alpha-3
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Christopher Smith
• Created: 14/Jun/15 00:55
• Updated: 03/Feb/22 22:42
• Resolved: 11/Oct/21 17:17

Description

I believe this is a special case of a general problem with generics and the type checker.

When I attempt to call a method doSomething(Map<String,Object> params) with a Groovy inline map, the type checker constructs the map's types as the immediate greatest-common-superclass of the values provided. For example, this map:

[ val1: 3, val2: 5 ]

is always considered to be a LinkedHashMap<String,Integer>, which can't be passed to the above method. In some, but not all, cases using an explicit as Map<String,Object> will work.

In the circumstance where an inline map or other generic collection is assigned to a variable or used as a method parameter, the type checker should be able to relax the inferred generic type bound to match the expected bound.