[GROOVY-7364] Invalid type inference with a generic method / return type and optional parameter

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.2
• Fix Version/s: 2.4.3
• Component/s: Static Type Checker
• Environment: MacOS X; Oracle JDK 1.7u75 / 18u40; Maven 3.0.5
• Assignee: Cédric Champeau
• Reporter: Frank Pavageau
• Created: 23/Mar/15 06:07
• Updated: 31/Mar/15 06:08
• Resolved: 23/Mar/15 06:44

Description

The following class fails to compile:

@TypeChecked
class A {
    public <T> T f(T value, int param = 0) {
        value
    }

    void run() {
        def s = f('42')
        s.length()
    }
}

The compilation error is:

[ERROR] /Users/fpavageau/devs/bugs/generic-method-optional-param/src/main/groovy/A.groovy: 26: [Static type checking] - Cannot find matching method java.lang.Object#length(). Please check if the declared type is right and if the method exists.
[ERROR] @ line 26, column 9.
[ERROR] s.length()
[ERROR] ^
[ERROR] 
[ERROR] 1 error

The same code will compile if the optional parameter is removed from f, or if s is explicitely declared as a String instead of using def.

It seems to be related to GROOVY-7211, but this bug is definitely not fixed in 2.4.2.

I'm attaching a test case, which is also available on Github.