[GROOVY-10725] Regression in STC related to generics, unknown cause

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.12
• Fix Version/s: 4.0.5, 2.5.19, 3.0.13
• Component/s: Static Type Checker
• Environment: Linux, Groovy 3.0.12, Java 8
• Assignee: Eric Milles
• Reporter: Octavia Togami
• Created: 19/Aug/22 22:09
• Updated: 10/Feb/23 21:40
• Resolved: 20/Aug/22 14:27

Description

In 3.0.12 the following code fails to pass STC:

@groovy.transform.CompileStatic
class Request {
    Enumeration<String> getHeaderNames() { 
       def r = new Vector()
       r.add("Header")
       r.elements()
    }
    String getHeader(String header) {
       "value"
    }
}

@groovy.transform.CompileStatic
class Test {
   void test() {
      def request = new Request()
      Set<Map<String, String>> allHeaders = []
      allHeaders.addAll(request.getHeaderNames().toList().collectEntries { headerName -> [headerName, request.getHeader(headerName)] })
   }
}

new Test().test()

Error:

$ groovy fail.groovy
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
/home/octy/Documents/groovy_playground/fail.groovy: 18: [Static type checking] - Cannot call <T> java.util.Set <Map>#addAll(T[]) with arguments [java.lang.Object]
 @ line 18, column 7.
         allHeaders.addAll(request.getHeaderNames().toList().collectEntries { headerName -> [headerName, request.getHeader(headerName)] })
         ^

1 error

This is not a total blocker, as the generics can be specified to `collectEntries`, or the expression extracted to a typed variable; and the error will go away. However, it does make existing code fail to compile, when it worked under 3.0.11.