Change behavior of equals/hashCode on adapted function references

Function references are now equal if they refer to the same function,
and if the parameter/return type adaptation, which happens when a
reference is used where some function type is expected, is exactly the
same. This includes the number of expected positional parameters (which
can be affected by defaults/varargs), whether the coercion of vararg
parameter to Array type happened, and whether the coercion of return
type to Unit happened.

 #KT-37543 Fixed

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/CallableReference.java

@@ -62,20 +62,16 @@ public abstract class CallableReference implements KCallable, Serializable {
 
     @SinceKotlin(version = "1.1")
     protected CallableReference(Object receiver) {
-        this(receiver, null, null, null, 0);
+        this(receiver, null, null, null, false);
     }
 
-    /**
-     * @param flags Bitmask where bits represent the following flags:<br/>
-     *              <li><ul>0 - the owner of this reference is a package, not a class.</ul></li>
-     */
     @SinceKotlin(version = "1.4")
-    protected CallableReference(Object receiver, Class owner, String name, String signature, int flags) {
+    protected CallableReference(Object receiver, Class owner, String name, String signature, boolean isTopLevel) {
         this.receiver = receiver;
         this.owner = owner;
         this.name = name;
         this.signature = signature;
-        this.isTopLevel = (flags & 1) == 1;
+        this.isTopLevel = isTopLevel;
     }
 
     protected abstract KCallable computeReflected();

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/FunctionReference.java

@@ -13,8 +13,26 @@ import kotlin.reflect.KFunction;
 public class FunctionReference extends CallableReference implements FunctionBase, KFunction {
     private final int arity;
 
+    /**
+     * Bitmask where bits represent the following flags:<br/>
+     * <li>
+     *     <ul>0 - whether the vararg to element parameter type conversion happened, i.e.<pre>
+     *         fun target(vararg xs: Int) {}
+     *         fun use(f: (Int, Int, Int) -> Unit) {}
+     *         use(::target)
+     *     </pre></ul>
+     *     <ul>1 - whether coercion of return type to Unit happened, i.e.<pre>
+     *         fun target(): Boolean = true
+     *         fun use(f: () -> Unit) {}
+     *         use(::target)
+     *     </pre></ul>
+     * </li>
+     */
+    @SinceKotlin(version = "1.4")
+    private final int flags;
+
     public FunctionReference(int arity) {
-        this.arity = arity;
+        this(arity, NO_RECEIVER, null, null, null, 0);
     }
 
     @SinceKotlin(version = "1.1")
@@ -24,8 +42,9 @@ public class FunctionReference extends CallableReference implements FunctionBase
 
     @SinceKotlin(version = "1.4")
     public FunctionReference(int arity, Object receiver, Class owner, String name, String signature, int flags) {
-        super(receiver, owner, name, signature, flags);
+        super(receiver, owner, name, signature, (flags & 1) == 1);
         this.arity = arity;
+        this.flags = flags >> 1;
     }
 
     @Override
@@ -81,9 +100,11 @@ public class FunctionReference extends CallableReference implements FunctionBase
         if (obj instanceof FunctionReference) {
             FunctionReference other = (FunctionReference) obj;
 
-            return (getOwner() == null ? other.getOwner() == null : getOwner().equals(other.getOwner())) &&
+            return Intrinsics.areEqual(getOwner(), other.getOwner()) &&
                    getName().equals(other.getName()) &&
                    getSignature().equals(other.getSignature()) &&
+                   flags == other.flags &&
+                   arity == other.arity &&
                    Intrinsics.areEqual(getBoundReceiver(), other.getBoundReceiver());
         }
         if (obj instanceof KFunction) {

libraries/stdlib/jvm/runtime/kotlin/jvm/internal/PropertyReference.java

@@ -22,7 +22,7 @@ public abstract class PropertyReference extends CallableReference implements KPr
 
     @SinceKotlin(version = "1.4")
     public PropertyReference(Object receiver, Class owner, String name, String signature, int flags) {
-        super(receiver, owner, name, signature, flags);
+        super(receiver, owner, name, signature, (flags & 1) == 1);
     }
 
     @Override