K2: Change resolution rules of when/if expressions with expected type

When expected type is known, use it as expected type for branch bodies.
While it indeed becomes different from the usual select call resolution,
where expected type is applied only after completion starts,
it helps to support, e.g. callable references resolution just as powerful
as it was in K1.

Also, in some cases where diagnostics have been changed, they become
a bit more helpful since they are reported closer
to the problematic places

cannotCastToFunction.kt test has been removed because it relied
on the case erroneously supported by the hack removed from
the FirCallResolver in this commit.

^KT-45989 Fixed
^KT-55936 Fixed
^KT-56445 Fixed
^KT-54709 Related
^KT-55931 Related

compiler/testData/diagnostics/tests/callableReference/adapted/adaptationByExpectTypeOutsideCall.fir.kt

@@ -0,0 +1,30 @@
+// SKIP_TXT
+fun baz(options: String = ""): String = ""
+fun bar(normalizeNames: Boolean = false): String = ""
+
+fun <E> select(x: E, y: E) = x
+fun <E> id(e: E): E = e
+
+fun runForString(x: () -> String) {}
+
+val cs: CharSequence = ""
+
+fun foo(dumpStrategy: String) {
+    val dump0: () -> String = ::baz // TYPE_MISMATCH
+    val dump1: () -> String = <!INITIALIZER_TYPE_MISMATCH, TYPE_MISMATCH!>id(::baz)<!> // TYPE_MISMATCH
+    // OK, TYPE_MISMATCH IN K2
+    val dump2: () -> String = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+    val dump3: () -> String = <!INITIALIZER_TYPE_MISMATCH, TYPE_MISMATCH, TYPE_MISMATCH!>select(::baz, ::bar)<!> // TYPE_MISMATCH
+
+    var dump4: () -> String = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+    dump4.invoke()
+    dump4 = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+
+    var dump5: () -> CharSequence = { cs }
+    expectString(<!ARGUMENT_TYPE_MISMATCH!>dump5.invoke()<!>)
+    dump5 = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+    // `dump5` should have smart cast to () -> String
+    expectString(dump5.invoke())
+}
+
+fun expectString(x: String) {}

compiler/testData/diagnostics/tests/callableReference/adapted/adaptationByExpectTypeOutsideCall.kt

@@ -0,0 +1,30 @@
+// SKIP_TXT
+fun baz(options: String = ""): String = ""
+fun bar(normalizeNames: Boolean = false): String = ""
+
+fun <E> select(x: E, y: E) = x
+fun <E> id(e: E): E = e
+
+fun runForString(x: () -> String) {}
+
+val cs: CharSequence = ""
+
+fun foo(dumpStrategy: String) {
+    val dump0: () -> String = <!TYPE_MISMATCH!>::<!TYPE_MISMATCH!>baz<!><!> // TYPE_MISMATCH
+    val dump1: () -> String = <!TYPE_MISMATCH, TYPE_MISMATCH!>id(::baz)<!> // TYPE_MISMATCH
+    // OK, TYPE_MISMATCH IN K2
+    val dump2: () -> String = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+    val dump3: () -> String = <!TYPE_MISMATCH, TYPE_MISMATCH, TYPE_MISMATCH!>select(::baz, ::bar)<!> // TYPE_MISMATCH
+
+    var dump4: () -> String = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+    dump4.invoke()
+    dump4 = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+
+    var dump5: () -> CharSequence = { cs }
+    expectString(<!TYPE_MISMATCH!>dump5.invoke()<!>)
+    dump5 = if (dumpStrategy == "KotlinLike") ::baz else ::bar
+    // `dump5` should have smart cast to () -> String
+    expectString(<!DEBUG_INFO_SMARTCAST!>dump5<!>.invoke())
+}
+
+fun expectString(x: String) {}

compiler/testData/diagnostics/tests/callableReference/adapted/adaptationInWhenWithMapOf.kt

@@ -0,0 +1,14 @@
+// FIR_IDENTICAL
+// SKIP_TXT
+// WITH_STDLIB
+// ISSUE: KT-56445
+
+fun foo(x: Int?, y: Int = 1) {}
+fun bar() {}
+
+fun test() {
+    mapOf( // String, KFunction<Unit>
+        "a" to ::foo,
+        "b" to ::bar,
+    )
+}

compiler/testData/diagnostics/tests/callableReference/adapted/noKFunctionForAdaptation.fir.kt

@@ -10,7 +10,7 @@ fun dump(dumpStrategy: String) {
 
     val f0: Function0<String> = <!INAPPLICABLE_CANDIDATE!>returnAdapter<!>(::<!UNRESOLVED_REFERENCE!>foo<!>)
     val f1: Function0<String> = ::foo
-    val f2: Function0<String> = if (dumpStrategy == "KotlinLike") ::<!UNRESOLVED_REFERENCE!>foo<!> else ::<!UNRESOLVED_REFERENCE!>bar<!>
+    val f2: Function0<String> = if (dumpStrategy == "KotlinLike") ::foo else ::bar
 }
 
 fun returnAdapter(a: kotlin.reflect.KFunction0<String>) = a