[GROOVY-7934] Type inference breaks for Collection.inject

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.4.6
• Labels: CompileStatic
• Assignee: Eric Milles
• Reporter: Oliver Holp
• Created: 12/Sep/16 09:33
• Updated: 20/Dec/23 14:03

Description

The code below should not compile as the first parameter to the inject method must be a string, but the integer 0 is handed in:

@CompileStatic
public static void main(String[] args) {
    def inList = ["a", "b", "c"]
    def outList = inList.inject(0, { a, b -> a + "," + b })
    println(outList)
}

I opened this issue as adviced in the reply to the same issue I asked on stackoverflow: http://stackoverflow.com/questions/39444838/chance-for-this-hole-in-groovy-staic-typing-to-be-fixed/39446458#39446458

Java streams example (from link):

var list = java.util.Arrays.asList("a", "b", "c");
var out = list.stream().reduce(0, (x,y) -> x + y);
System.out.println(out);

NOTE: You can use java streams apis in groovy:

@groovy.transform.CompileStatic
void test() {
  def list = ['a','b','c']
  def str = list.stream().reduce("", (x,y) -> x + y) // STC error if "" is 0
  println str
}
test()

Issue Links

• is related to: GROOVY-5893 Return type of "inject" is not inferred properly
• is related to: GROOVY-6504 Type checker select the wrong inject method
• is related to: GROOVY-5924 Provide a mechanism to allow the type checker to know what are the expected argument types of a closure