Added captured types and approximation

CapturedType captures type projection while solving the constraint system.
During the substitution type containing captured types is approximated
to get rid of captured types and (for simple cases) replace them with corresponding type projections.

Note that Array<Array< CapturedType(out Int) >> is (over)approximated by Array<out<Array<out Int>>

See 'Mixed-site variance' by Ross Tate for details.

 #KT-2570 Fixed
 #KT-2872 Fixed
 #KT-3213 Fixed

compiler/testData/diagnostics/tests/inference/capturedTypes/captureForPlatformTypes.kt

@@ -0,0 +1,29 @@
+// !CHECK_TYPE
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// FILE: A.java
+public class A {
+    public static <T> Class<T> foo(Class<T> clazz) {
+        return clazz;
+    }
+
+    public static <T> Class<Class<T>> bar(Class<T> clazz) {
+        throw new Exception();
+    }
+}
+
+// FILE: b.kt
+fun test1(clazz: Class<out Int>) {
+    val foo0: Class<out Int> = A.foo(clazz)
+    val foo1 = A.foo(clazz)
+    foo1 checkType { it: _< Class<out Int> > }
+//    should be ok
+    foo1 checkType { <!TYPE_MISMATCH!>it<!>: _< Class<out Int?> > }
+}
+
+fun tes2t(clazz: Class<in Int>) {
+    val foo0: Class<out Class<in Int>> = A.bar(clazz)
+    val foo1 = A.bar(clazz)
+    foo1 checkType { it: _< Class<out Class<in Int>> > }
+//    should be ok
+    foo1 checkType { <!TYPE_MISMATCH!>it<!>: _< Class<out Class<in Int?>> > }
+}

compiler/testData/diagnostics/tests/inference/capturedTypes/captureForPlatformTypes.txt

@@ -0,0 +1,15 @@
+package
+
+internal fun tes2t(/*0*/ clazz: java.lang.Class<in kotlin.Int>): kotlin.Unit
+internal fun test1(/*0*/ clazz: java.lang.Class<out kotlin.Int>): kotlin.Unit
+
+public open class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    // Static members
+    public open fun </*0*/ T> bar(/*0*/ clazz: java.lang.Class<T!>!): java.lang.Class<java.lang.Class<T!>!>!
+    public open fun </*0*/ T> foo(/*0*/ clazz: java.lang.Class<T!>!): java.lang.Class<T!>!
+}

compiler/testData/diagnostics/tests/inference/capturedTypes/capturedType.kt

@@ -0,0 +1,16 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -UNUSED_PARAMETER
+// !CHECK_TYPE
+
+fun <T> foo(array: Array<T>): Array<T> = array
+
+fun test1(a1: Array<out Int>) {
+    val b1: Array<out Int> = foo(a1)
+    val c1 = foo(a1)
+    c1 checkType { it : _<Array<out Int>> }
+}
+
+fun test2(a2: Array<in Int>) {
+    val b2: Array<in Int> = foo(a2)
+    val c2 = foo(a2)
+    c2 checkType { it : _<Array<in Int>> }
+}

compiler/testData/diagnostics/tests/inference/capturedTypes/capturedType.txt

@@ -0,0 +1,5 @@
+package
+
+internal fun </*0*/ T> foo(/*0*/ array: kotlin.Array<T>): kotlin.Array<T>
+internal fun test1(/*0*/ a1: kotlin.Array<out kotlin.Int>): kotlin.Unit
+internal fun test2(/*0*/ a2: kotlin.Array<in kotlin.Int>): kotlin.Unit

compiler/testData/diagnostics/tests/inference/capturedTypes/capturedTypeAndApproximation.kt

@@ -0,0 +1,16 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -UNUSED_PARAMETER
+// !CHECK_TYPE
+
+fun <T> foo(a: Array<T>): Array<Array<T>> = throw Exception()
+
+fun test1(a1: Array<out Int>) {
+    val b1: Array<out Array<out Int>> = foo(a1)
+    val c1 = foo(a1)
+    c1 checkType { it : _<Array<out Array<out Int>>> }
+}
+
+fun test2(a2: Array<in Int>) {
+    val b2: Array<out Array<in Int>> = foo(a2)
+    val c2 = foo(a2)
+    c2 checkType { it : _<Array<out Array<in Int>>> }
+}

compiler/testData/diagnostics/tests/inference/capturedTypes/capturedTypeAndApproximation.txt

@@ -0,0 +1,5 @@
+package
+
+internal fun </*0*/ T> foo(/*0*/ a: kotlin.Array<T>): kotlin.Array<kotlin.Array<T>>
+internal fun test1(/*0*/ a1: kotlin.Array<out kotlin.Int>): kotlin.Unit
+internal fun test2(/*0*/ a2: kotlin.Array<in kotlin.Int>): kotlin.Unit

compiler/testData/diagnostics/tests/inference/capturedTypes/kt2570.kt

@@ -0,0 +1,9 @@
+// !CHECK_TYPE
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+fun <T> foo(l: MutableList<T>): MutableList<T> = l
+fun test(l: MutableList<out Int>) {
+    val a: MutableList<out Int> = foo(l)
+    val b = foo(l)
+    b checkType { it: _< MutableList<out Int> > }
+}

compiler/testData/diagnostics/tests/inference/capturedTypes/kt2570.txt

@@ -0,0 +1,4 @@
+package
+
+internal fun </*0*/ T> foo(/*0*/ l: kotlin.MutableList<T>): kotlin.MutableList<T>
+internal fun test(/*0*/ l: kotlin.MutableList<out kotlin.Int>): kotlin.Unit

compiler/testData/diagnostics/tests/inference/capturedTypes/kt2872.kt

@@ -0,0 +1,6 @@
+fun <T> Array<T>.foo() {}
+
+fun test(array: Array<out Int>) {
+    array.foo()
+    <!TYPE_MISMATCH!>array<!>.foo<<!PROJECTION_ON_NON_CLASS_TYPE_ARGUMENT!>out<!> Int>()
+}

compiler/testData/diagnostics/tests/inference/capturedTypes/kt2872.txt

@@ -0,0 +1,4 @@
+package
+
+internal fun test(/*0*/ array: kotlin.Array<out kotlin.Int>): kotlin.Unit
+internal fun </*0*/ T> kotlin.Array<T>.foo(): kotlin.Unit