To fix imports of missing types, we have to test for these type-usage-patterns and see which information we get from the
groovy-compiler:

1.) create a new type with dflt. constructor:

    MyType t = new MyType()

2.) create a new type with special constructor:

    MyType t = new MyType(input)

3.) Access static method of type:

    result = MyType.staticMethod(input)

4.) Access public field of unknown type:

    result = MyType.fieldVar

5.) .class access of unknown type:

    Class x = MyType.class

6.) declare class in parameters:

    void testFct(MyType m) { }

7.) Reflection access/query:

    Class.forName((MyType);

To implement group of related features we have to provide this to the user:

1.) Add missing imports
2.) Provide drop-down box if multiple candidates exist
3.) Hint provider for missing *and* unused imports
4.) Remove unused imports

The corresponding code in the Java editor can be found here:

java.editor/src/org/netbeans/modules/java/editor/imports

OK - here are the corresponding groovy errer-messages:

//------------------------------------------------------------------------------------
//1.) create a new type with dflt. constructor:

MyType t = new MyType()

// gives: "unable to resolve class" at compile-time
// Found: COMPILE-TIME

//------------------------------------------------------------------------------------
//2.) create a new type with special constructor:
//    gives: 

String t2 = new String(1L)

//Caught: groovy.lang.GroovyRuntimeException: failed to invoke constructor: public java.lang.String(byte[]) with
arguments: {[1]} reason: java.lang.IllegalArgumentException: argument type mismatch
//        at unresolvedTypes.run(unresolvedTypes.groovy:17)
//        at unresolvedTypes.main(unresolvedTypes.groovy)

// Found: RUN-TIME

//------------------------------------------------------------------------------------
//3.) Access static method of type:
//    gives:

String.valueOf2(true)

//Caught: groovy.lang.MissingMethodException: No signature of method: static java.lang.String.valueOf2() is applicable
for argument types: (java.lang.Boolean) values: {true}
//        at unresolvedTypes.run(unresolvedTypes.groovy:27)
//        at unresolvedTypes.main(unresolvedTypes.groovy)

// Found: RUN-TIME

//------------------------------------------------------------------------------------
//4.) Access public field of unknown type:
//    gives:

System.out2

//Caught: groovy.lang.MissingPropertyException: No such property: out2 for class: java.lang.System
//        at unresolvedTypes.run(unresolvedTypes.groovy:5)
//        at unresolvedTypes.main(unresolvedTypes.groovy)

// Found: RUN-TIME

//------------------------------------------------------------------------------------
//5.) .class access of unknown type:
//    gives:

Class x = UnknownType.class

//Caught: groovy.lang.MissingPropertyException: No such property: UnknownType for class: unresolvedTypes
//        at unresolvedTypes.main(unresolvedTypes.groovy)

// Found: RUN-TIME

//------------------------------------------------------------------------------------
//6.) declare class in parameters:
//    gives:

void testFct(MyType m) { }

// gives: "unable to resolve class" at compile-time
// Found: COMPILE-TIME


//------------------------------------------------------------------------------------
//7.) Reflection access/query:
//    gives:

Class t3 = Class.forName("java.lang.Thread4")

//Caught: java.lang.ClassNotFoundException: java.lang.Thread4
//        at unresolvedTypes.run(unresolvedTypes.groovy:76)
//        at unresolvedTypes.main(unresolvedTypes.groovy)

// Found: RUN-TIME

OK, this one should be fixed now:

http://hg.netbeans.org/main/contrib/rev/06bb7da58c96
http://hg.netbeans.org/main/contrib/rev/a7d658f97499
http://hg.netbeans.org/main/contrib/rev/7ad45d82386f
http://hg.netbeans.org/main/contrib/rev/13ace1d25379
...

v., see issue 149948