[GROOVY-10339] STC instantiates parameterized function with a wrong type leading to unsoundness

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-rc-1, 2.5.21, 3.0.15
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 01/Nov/21 13:24
• Updated: 12/Jan/23 20:43
• Resolved: 12/Nov/21 14:54

Description

I have the following program

class Test {
  static <T> T bar(T x, T y) { return x; }

  static String m() { return ""; }

  static void main(String[] args) {
     Integer x = bar(m(), 1); // STC misses the error.
  }
}

Actual behaviour

groovyc incorrectly accepts the above program, although it contains a type error at line7. This leads to the following exception at runtime:

Exception in thread "main" org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '' with class 'java.lang.String' to class 'java.lang.Integer'
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToNumber(DefaultTypeTransformation.java:179)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnNumber(DefaultTypeTransformation.java:294)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToType(DefaultTypeTransformation.java:251)
        at org.codehaus.groovy.vmplugin.v8.IndyInterface.fromCache(IndyInterface.java:318)
        at Test.main(test.groovy:7)

Expected behaviour

The compiler should have rejected the program.

Tested against master.