[GROOVY-9420] Incorrect type inference on map[key]

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.5.9
• Fix Version/s: 4.0.0-alpha-1, 3.0.2
• Component/s: Static Type Checker
• Assignee: Paul King
• Reporter: Mauro Molinari
• Created: 25/Feb/20 08:52
• Updated: 17/Aug/22 18:49
• Resolved: 29/Feb/20 09:10

Description

Consider this example:

 

package test58

import groovy.transform.CompileStatic;

@CompileStatic
public class Test58 {

	Map<String, String> m = [
		foo: 'foo'
		]
		
	void blah() {
		Object c = boh()
		def a = m.get(c)
		uhuh(a)
		def b = m[c]
		uhuh(b)
	}
	
	void uhuh(String a) {
	}
	
	Object boh() {
		'foo'
	}
}

The call uhuh(b) fails with error:

Groovy:[Static type checking] - Cannot find matching method test58.Test58#uhuh(java.lang.Object). Please check if the declared type is correct and if the method exists.

However, since m is a Map<String, String>, b type should be inferred as String.
If an error is in this code, I think it should be signalled on the def b = m[c] assignment (or even def a = m.get(c)), because c declared type is Object, and not on the subsequent call involving b.
Perhaps here c is inferred as String thanks to flow typing, but then I still believe uhuh(b) should succeed, just like uhuh(a) does.

Originally submitted for Groovy Eclipse Plugin at: https://github.com/groovy/groovy-eclipse/issues/948

Issue Links

• relates to: GROOVY-8788 Inconsistency in extension method selection with @CompileStatic
• links to: GitHub Pull Request #1175