[GROOVY-7582] Closure to SAM coercion doesn't handle overloads with different SAM signatures

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.4
• Fix Version/s: 4.0.0-alpha-3
• Assignee: Eric Milles
• Reporter: Luke Daley
• Created: 08/Sep/15 01:28
• Updated: 15/Jan/24 14:07
• Resolved: 26/Sep/21 20:34

Description

The following…

interface Action<T> {
  void exec(T thing)
}

interface Block {
  void exec()
}

class Container {
  void m(Action<?> action) {}
  void m(Block block) {} 
}

def c = new Container()

c.m { -> 1 }

Yields…

groovy.lang.GroovyRuntimeException: Ambiguous method overloading for method Container#m.
Cannot resolve which method to invoke for [class ConsoleScript0$_run_closure1] due to overlapping prototypes between:
	[interface Action]
	[interface Block]
	at ConsoleScript0.run(ConsoleScript0:16)

It seems that Groovy should be able to deal with the case where the SAM parameter signatures are different. Java does this with lambda expressions. That is, the following works in Java…

Container c = new Container();
c.m(() -> {});
c.m(arg -> {});

Issue Links

• relates to: GROOVY-11010 Ambiguous method reference when expecting a SAM type
• relates to: GROOVY-11121 unexpected error when having overloaded methods, one of which receiving an Iterable