[GROOVY-8757] Incorrect bytecode produced after compiling class implementing trait with generic method

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.4.15, 3.0.0-alpha-3, 2.5.2
• Fix Version/s: 2.4.16, 3.0.0-alpha-4, 2.5.3
• Component/s: Compiler
• Assignee: Paul King
• Reporter: Daniil Ovchinnikov
• Created: 20/Aug/18 17:22
• Updated: 13/Dec/18 10:02
• Resolved: 26/Aug/18 01:20

Description

T.groovy

trait T {
    def <T extends Number> T foo(Class<T> c) {
        println c
        return null 
    }
}

C.groovy

class C implements T {}

usage.groovy

new C().foo(Integer)

$ groovyc C.groovy T.groovy
$ groovy usage.groovy
class java.lang.Integer
$ groovyc C.groovy # recompile C using already compiled T
$ groovy usage.groovy
Caught: java.lang.VerifyError: Bad return type
Exception Details:
  Location:
    C.foo(Ljava/lang/Class;)Ljava/lang/Number; @5: areturn
  Reason:
    Type 'java/lang/Object' (current frame, stack[0]) is not assignable to 'java/lang/Number' (from method signature)
  Current Frame:
    bci: @5
    flags: { }
    locals: { 'C', 'java/lang/Class' }
    stack: { 'java/lang/Object' }
  Bytecode:
    0x0000000: 2a2b b600 88b0

java.lang.VerifyError: Bad return type
Exception Details:
  Location:
    C.foo(Ljava/lang/Class;)Ljava/lang/Number; @5: areturn
  Reason:
    Type 'java/lang/Object' (current frame, stack[0]) is not assignable to 'java/lang/Number' (from method signature)
  Current Frame:
    bci: @5
    flags: { }
    locals: { 'C', 'java/lang/Class' }
    stack: { 'java/lang/Object' }
  Bytecode:
    0x0000000: 2a2b b600 88b0

	at usage.run(usage.groovy:1)

original javap output

public class C implements T,groovy.lang.GroovyObject {
  public static transient boolean __$stMC;
  public C();
  public <T extends java.lang.Number> T foo(java.lang.Class<T>);
  public <T extends java.lang.Number> T Ttrait$super$foo(java.lang.Class<T>);
  static {};
  protected groovy.lang.MetaClass $getStaticMetaClass();
  public groovy.lang.MetaClass getMetaClass();
  public void setMetaClass(groovy.lang.MetaClass);
  public java.lang.Object invokeMethod(java.lang.String, java.lang.Object);
  public java.lang.Object getProperty(java.lang.String);
  public void setProperty(java.lang.String, java.lang.Object);
}

recompiled javap output

public class C implements T,groovy.lang.GroovyObject {
  public static transient boolean __$stMC;
  public C();
  public <T> T foo(java.lang.Class<T>);
  public <T extends java.lang.Number> T Ttrait$super$foo(java.lang.Class<T>);
  static {};
  protected groovy.lang.MetaClass $getStaticMetaClass();
  public groovy.lang.MetaClass getMetaClass();
  public void setMetaClass(groovy.lang.MetaClass);
  public java.lang.Object invokeMethod(java.lang.String, java.lang.Object);
  public java.lang.Object getProperty(java.lang.String);
  public void setProperty(java.lang.String, java.lang.Object);
  public java.lang.Number foo(java.lang.Class);
}

Issue Links

• links to: GitHub Pull Request #788