Fix type inference issues for 'if' and 'when'.

Use 'expectedType' (when present) as an explicit type argument for a special construct call.
Unfortunately, this approach can't be used for elvis due to other elvis-related inference hacks.
Fixes KT-10807, KT-10811.
This also affects KT-6189: now we can infer proper type for 'if'.

If type inference for special call failed, and we found no type errors in sub-expressions,
report TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT error.
This (and the hack above) fixes KT-10809: code no longer compiles.

compiler/testData/diagnostics/tests/when/kt10809.kt

@@ -0,0 +1,50 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER -DEBUG_INFO_SMARTCAST
+
+interface Data
+interface Item
+class FlagData(val value: Boolean) : Data
+class ListData<T : Item>(val list: List<T>) : Data
+
+fun <T> listOf(vararg items: T): List<T> = null!!
+
+fun test1(o: Any) = <!TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT!>when<!> (o) {
+    is List<*> ->
+        ListData(listOf())
+    is Int -> when {
+        o < 0 ->
+            FlagData(true)
+        else ->
+            null
+    }
+    else ->
+        null
+}
+
+fun test1x(o: Any): Data? = when (o) {
+    is List<*> ->
+        ListData(listOf())
+    is Int -> when {
+        o < 0 ->
+            FlagData(true)
+        else ->
+            null
+    }
+    else ->
+        null
+}
+
+fun test2() =
+        <!TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT!>if<!> (true)
+            ListData(listOf())
+        else
+            FlagData(true)
+
+fun test2x(): Data =
+        if (true) ListData(listOf()) else FlagData(true)
+
+fun test2y(): Any =
+        if (true) ListData(listOf()) else FlagData(true)
+
+fun test2z(): Any =
+        run { if (true) ListData(listOf()) else FlagData(true) }
+

compiler/testData/diagnostics/tests/when/kt10809.txt

@@ -0,0 +1,37 @@
+package
+
+public fun </*0*/ T> listOf(/*0*/ vararg items: T /*kotlin.Array<out T>*/): kotlin.collections.List<T>
+public fun test1(/*0*/ o: kotlin.Any): ???
+public fun test1x(/*0*/ o: kotlin.Any): Data?
+public fun test2(): ???
+public fun test2x(): Data
+public fun test2y(): kotlin.Any
+public fun test2z(): kotlin.Any
+
+public interface Data {
+    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
+}
+
+public final class FlagData : Data {
+    public constructor FlagData(/*0*/ value: kotlin.Boolean)
+    public final val value: kotlin.Boolean
+    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
+}
+
+public interface Item {
+    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
+}
+
+public final class ListData</*0*/ T : Item> : Data {
+    public constructor ListData</*0*/ T : Item>(/*0*/ list: kotlin.collections.List<T>)
+    public final val list: kotlin.collections.List<T>
+    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
+}

compiler/testData/diagnostics/tests/when/kt10811.kt

@@ -0,0 +1,24 @@
+interface Maybe<T>
+class Some<T>(val value: T) : Maybe<T>
+class None<T> : Maybe<T>
+
+fun <T> none() : None<T> = TODO()
+
+fun test1() : Maybe<String?> = if (true) none() else Some("")
+
+fun test2() : Maybe<String?> = when {
+    true -> none()
+    else -> Some("")
+}
+
+fun test3() : Maybe<String?> = when {
+    true -> none()
+    else -> Some<String?>("")
+}
+
+fun test4() : Maybe<String?> {
+    when ("") {
+        "a" -> return none()
+        else -> return Some<String?>("")
+    }
+}

compiler/testData/diagnostics/tests/when/kt10811.txt

@@ -0,0 +1,28 @@
+package
+
+public fun </*0*/ T> none(): None<T>
+public fun test1(): Maybe<kotlin.String?>
+public fun test2(): Maybe<kotlin.String?>
+public fun test3(): Maybe<kotlin.String?>
+public fun test4(): Maybe<kotlin.String?>
+
+public interface Maybe</*0*/ T> {
+    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
+}
+
+public final class None</*0*/ T> : Maybe<T> {
+    public constructor None</*0*/ T>()
+    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
+}
+
+public final class Some</*0*/ T> : Maybe<T> {
+    public constructor Some</*0*/ T>(/*0*/ value: T)
+    public final val value: T
+    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
+}

compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt

@@ -0,0 +1,24 @@
+val test1: (String) -> Boolean =
+        when {
+            true -> {{ true }}
+            else -> {{ false }}
+        }
+
+val test2: (String) -> Boolean =
+        when {
+            true -> {{ true }}
+            else -> null!!
+        }
+
+val test3: (String) -> Boolean =
+        when {
+            true -> { s -> true }
+            else -> null!!
+        }
+
+val test4: (String) -> Boolean =
+        when {
+            true -> { <!EXPECTED_PARAMETERS_NUMBER_MISMATCH!>s1, <!CANNOT_INFER_PARAMETER_TYPE!>s2<!><!> -> true }
+            else -> null!!
+        }
+

compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.txt

@@ -0,0 +1,6 @@
+package
+
+public val test1: (kotlin.String) -> kotlin.Boolean
+public val test2: (kotlin.String) -> kotlin.Boolean
+public val test3: (kotlin.String) -> kotlin.Boolean
+public val test4: (kotlin.String) -> kotlin.Boolean