Add InlineBytecodeTests for #6375

Author: nicolasstucki

compiler/test/dotty/tools/backend/jvm/InlineBytecodeTests.scala

@@ -320,4 +320,40 @@ class InlineBytecodeTests extends DottyBytecodeTest {
 
     }
   }
+
+  @Test def i6375 = {
+    val source = """class Test:
+                   |  given Int = 0
+                   |  def f(): Int ?=> Boolean = true : (Int ?=> Boolean)
+                   |  inline def g(): Int ?=> Boolean = true
+                   |  def test = g()
+                 """.stripMargin
+
+    checkBCode(source) { dir =>
+      val clsIn      = dir.lookupName("Test.class", directory = false).input
+      val clsNode    = loadClassNode(clsIn)
+
+      val fun = getMethod(clsNode, "test")
+      val instructions = instructionsFromMethod(fun)
+      val expected =
+        List(
+          // Head tested separatly
+          VarOp(ALOAD, 0),
+          Invoke(INVOKEVIRTUAL, "Test", "given_Int", "()I", false),
+          Invoke(INVOKESTATIC, "scala/runtime/BoxesRunTime", "boxToInteger", "(I)Ljava/lang/Integer;", false),
+          Invoke(INVOKEINTERFACE, "scala/Function1", "apply", "(Ljava/lang/Object;)Ljava/lang/Object;", true),
+          Invoke(INVOKESTATIC, "scala/runtime/BoxesRunTime", "unboxToBoolean", "(Ljava/lang/Object;)Z", false),
+          Op(IRETURN)
+        )
+
+      instructions.head match {
+        case InvokeDynamic(INVOKEDYNAMIC, "apply$mcZI$sp", "()Ldotty/runtime/function/JFunction1$mcZI$sp;", _, _) =>
+        case _ => assert(false, "`g` was not properly inlined in `test`\n")
+      }
+
+      assert(instructions.tail == expected,
+        "`fg was not properly inlined in `test`\n" + diffInstructions(instructions, expected))
+
+    }
+  }
 }