PSI2IR: Generate adapted callable references

Callable reference is "adapted" if it requires some adaptation to an
expected function type - e.g., when a reference to
```
  fun foo(vararg xs: Int): Int
```
is used where `(Int, Int, Int) -> Int` is expected.

For such callable references we generate the following IR (in
pseudo-Kotlin):
```
  {
    fun foo'(p0: Int, p1: Int, p2: Int): Int {
      return [| foo(p0, p1, p2) |]
    }
    ::foo'
  }
```

where `[| foo(p0, p1, p2) |]` is calling function `foo` with arguments
`p0`, `p1`, and `p2`, as they were mapped by callable reference
resolution.

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/NewCallArguments.kt

@@ -193,6 +193,18 @@ class FakePositionalValueArgumentForCallableReferenceImpl(
     override fun isExternal(): Boolean = false
 }
 
+class FakeImplicitSpreadValueArgumentForCallableReferenceImpl(
+    private val callElement: KtElement,
+    override val expression: ValueArgument
+) : FakeImplicitSpreadValueArgumentForCallableReference {
+    override fun getArgumentExpression(): KtExpression? = null
+    override fun getArgumentName(): ValueArgumentName? = null
+    override fun isNamed(): Boolean = false
+    override fun asElement(): KtElement = callElement
+    override fun getSpreadElement(): LeafPsiElement? = null // TODO callElement?
+    override fun isExternal(): Boolean = false
+}
+
 class EmptyLabeledReturn(
     val returnExpression: KtReturnExpression,
     builtIns: KotlinBuiltIns

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/ResolvedAtomCompleter.kt

@@ -7,7 +7,10 @@ package org.jetbrains.kotlin.resolve.calls.tower
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.builtins.createFunctionType
-import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.descriptors.CallableDescriptor
+import org.jetbrains.kotlin.descriptors.FunctionDescriptor
+import org.jetbrains.kotlin.descriptors.ModuleDescriptor
+import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.descriptors.impl.FunctionDescriptorImpl
 import org.jetbrains.kotlin.descriptors.impl.ReceiverParameterDescriptorImpl
 import org.jetbrains.kotlin.psi.KtElement
@@ -377,7 +380,11 @@ class ResolvedAtomCompleter(
                     is ResolvedCallArgument.SimpleArgument -> {
                         val valueArgument = makeFakeValueArgument(resolvedCallArgument.callArgument, callElement)
                         if (valueParameter.isVararg)
-                            VarargValueArgument(listOf(valueArgument))
+                            VarargValueArgument(
+                                listOf(
+                                    FakeImplicitSpreadValueArgumentForCallableReferenceImpl(callElement, valueArgument)
+                                )
+                            )
                         else
                             ExpressionValueArgument(valueArgument)
                     }