PatternMatchingTypingVisitor:

rewrite type inference for 'when' using special constructs.
This fixes several type inference issues for 'when':
KT-9929, KT-9972, KT-10439, KT-10463
along with some other diagnostics-related issues.

compiler/testData/diagnostics/tests/controlStructures/ifWhenWithoutElse.kt

@@ -22,7 +22,7 @@ val wxx1 = <!NO_ELSE_IN_WHEN!>when<!> { true -> 42 }
 val wxx2: Unit = <!NO_ELSE_IN_WHEN!>when<!> { true -> <!CONSTANT_EXPECTED_TYPE_MISMATCH!>42<!> }
 val wxx3 = idAny(<!NO_ELSE_IN_WHEN!>when<!> { true -> 42 })
 val wxx4 = id(<!NO_ELSE_IN_WHEN!>when<!> { true -> 42 })
-val wxx5 = idUnit(<!NO_ELSE_IN_WHEN!>when<!> { true -> 42 })
+val wxx5 = idUnit(<!NO_ELSE_IN_WHEN!>when<!> { true -> <!CONSTANT_EXPECTED_TYPE_MISMATCH!>42<!> })
 val wxx6 = null ?: <!NO_ELSE_IN_WHEN!>when<!> { true -> 42 }
 val wxx7 = "" + <!NO_ELSE_IN_WHEN!>when<!> { true -> 42 }
 

compiler/testData/diagnostics/tests/controlStructures/kt10706.kt

@@ -4,8 +4,8 @@ fun fn(c: Char?): Any? =
         if (c == null) TODO()
         else when (<!DEBUG_INFO_SMARTCAST!>c<!>) {
             'a' -> when (<!DEBUG_INFO_SMARTCAST!>c<!>) {
-                'B' -> <!IMPLICIT_CAST_TO_ANY!>1<!>
-                'C' -> <!IMPLICIT_CAST_TO_ANY!>"sdf"<!>
+                'B' -> 1
+                'C' -> "sdf"
                 else -> TODO()
             }
             else -> TODO()