Introduce FirInitializerTypeMismatchChecker

idea/testData/checker/QualifiedExpressions.fir.kt

@@ -3,7 +3,7 @@
 package qualified_expressions
 
 fun test(s: IntRange?) {
-   val a: Int = s?.start
+   val a: Int = <error descr="[INITIALIZER_TYPE_MISMATCH] Initializer type mismatch: expected kotlin/Int, actual kotlin/Int?">s?.start</error>
    val b: Int? = s?.start
    val c: Int = s?.start ?: -11
    val d: Int = s?.start ?: "empty"

idea/testData/checker/UnreachableCode.fir.kt

@@ -4,7 +4,7 @@ fun t1() : Int{
 }
 
 fun t1a() : Int {
-  return
+  <error descr="[RETURN_TYPE_MISMATCH] Return type mismatch: expected kotlin/Int, actual kotlin/Unit">return</error>
   return 1
   1
 }
@@ -17,7 +17,7 @@ fun t1b() : Int {
 
 fun t1c() : Int {
   return 1
-  return
+  <error descr="[RETURN_TYPE_MISMATCH] Return type mismatch: expected kotlin/Int, actual kotlin/Unit">return</error>
   1
 }
 

idea/testData/checker/Variance.fir.kt

@@ -7,13 +7,13 @@ abstract class Producer<out T> {}
 abstract class Usual<T> {}
 
 fun foo(c: Consumer<Int>, p: Producer<Int>, u: Usual<Int>) {
-    val c1: Consumer<Any> = c
+    val c1: Consumer<Any> = <error descr="[INITIALIZER_TYPE_MISMATCH] Initializer type mismatch: expected variance/Consumer<kotlin/Any>, actual variance/Consumer<kotlin/Int>">c</error>
     val c2: Consumer<Int> = c1
 
     val p1: Producer<Any> = p
     val p2: Producer<Int> = p1
 
-    val u1: Usual<Any> = u
+    val u1: Usual<Any> = <error descr="[INITIALIZER_TYPE_MISMATCH] Initializer type mismatch: expected variance/Usual<kotlin/Any>, actual variance/Usual<kotlin/Int>">u</error>
     val u2: Usual<Int> = u1
 }
 

idea/testData/checker/regression/kt303.fir.kt

@@ -8,4 +8,4 @@ open class Bar() : <error descr="[OTHER_ERROR] Unknown (other) error">Foo</error
 
 }
 
-val x : Int = Foo()
+val x : Int = <error descr="[INITIALIZER_TYPE_MISMATCH] Initializer type mismatch: expected kotlin/Int, actual Foo">Foo()</error>

idea/testData/checker/trivialHierarchyLoop.fir.kt

@@ -1,3 +1,3 @@
 class A : <error descr="[OTHER_ERROR] Unknown (other) error">A</error>() {}
 
-val x : Int = A()
+val x : Int = <error descr="[INITIALIZER_TYPE_MISMATCH] Initializer type mismatch: expected kotlin/Int, actual A">A()</error>