Simplify IrElement hierarchy.

IrDeclaration can be now hosted under IrExpression (as IrStatement).

compiler/testData/ir/irText/callWithReorderedArguments.txt

@@ -1,7 +1,7 @@
 IrFile /callWithReorderedArguments.kt
   IrFunction public fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.Int): kotlin.Unit
     IrExpressionBody
-      BLOCK type=kotlin.Unit
+      BLOCK type=kotlin.Unit hasResult=false isDesugared=false
   IrFunction public fun noReorder1(): kotlin.Int
     IrExpressionBody
       LITERAL Int type=kotlin.Int value='1'
@@ -16,17 +16,15 @@ IrFile /callWithReorderedArguments.kt
       LITERAL Int type=kotlin.Int value='2'
   IrFunction public fun test(): kotlin.Unit
     IrExpressionBody
-      BLOCK type=kotlin.Unit
+      BLOCK type=kotlin.Unit hasResult=false isDesugared=false
         CALL .foo type=kotlin.Unit operator=
           a: CALL .noReorder1 type=kotlin.Int operator=
           b: CALL .noReorder2 type=kotlin.Int operator=
-        BLOCK type=kotlin.Unit
-          LOCAL tmp0
-            IrLocalVariable val tmp0: kotlin.Int
-              CALL .reordered1 type=kotlin.Int operator=
-          LOCAL tmp1
-            IrLocalVariable val tmp1: kotlin.Int
-              CALL .reordered2 type=kotlin.Int operator=
+        BLOCK type=kotlin.Unit hasResult=false isDesugared=true
+          VAR val tmp0: kotlin.Int
+            CALL .reordered1 type=kotlin.Int operator=
+          VAR val tmp1: kotlin.Int
+            CALL .reordered2 type=kotlin.Int operator=
           CALL .foo type=kotlin.Unit operator=
             a: GET_VAR tmp1 type=kotlin.Int
             b: GET_VAR tmp0 type=kotlin.Int

compiler/testData/ir/irText/destructuring1.kt

@@ -0,0 +1,10 @@
+object A
+
+object B {
+    operator fun A.component1() = 1
+    operator fun A.component2() = 2
+}
+
+fun B.test() { // <<< destructuring1.txt
+    val (x, y) = A
+}

compiler/testData/ir/irText/destructuring1.txt

@@ -0,0 +1,4 @@
+IrFunction public fun B.test(): kotlin.Unit
+  IrExpressionBody
+    BLOCK type=kotlin.Unit hasResult=false isDesugared=false
+      DUMMY KtDestructuringDeclaration type=kotlin.Unit

compiler/testData/ir/irText/references.txt

@@ -17,10 +17,9 @@ IrFile /references.kt
       GET_VAR x type=kotlin.String
   IrFunction public fun test3(): kotlin.String
     IrExpressionBody
-      BLOCK type=kotlin.Nothing
-        LOCAL x
-          IrLocalVariable val x: kotlin.String = "OK"
-            LITERAL String type=kotlin.String value='OK'
+      BLOCK type=kotlin.Nothing hasResult=false isDesugared=false
+        VAR val x: kotlin.String = "OK"
+          LITERAL String type=kotlin.String value='OK'
         RETURN type=kotlin.Nothing
           GET_VAR x type=kotlin.String
   IrFunction public fun test4(): kotlin.String

compiler/testData/ir/irText/smoke.kt

@@ -1,6 +1,6 @@
 // <<< smoke.txt
 fun testFun(): String { return "OK" }
-val testSimpleVal = 1 // <<< smoke.testSimpleVal.txt
+val testSimpleVal = 1
 val testValWithGetter: Int get() = 42
 var testSimpleVar = 2
 var testVarWithAccessors: Int
@@ -13,4 +13,4 @@ var testVarWithAccessors: Int
 // 2 IrPropertyGetter
 // 1 IrPropertySetter
 // 1 IrProperty public var testSimpleVar
-// 1 IrProperty public var testVarWithAccessors
+// 1 IrProperty public var testVarWithAccessors

compiler/testData/ir/irText/smoke.testSimpleVal.txt

@@ -1,3 +0,0 @@
-IrProperty public val testSimpleVal: kotlin.Int = 1 getter=null setter=null
-  IrExpressionBody
-    LITERAL Int type=kotlin.Int value='1'

compiler/testData/ir/irText/smoke.txt

@@ -1,7 +1,7 @@
 IrFile /smoke.kt
   IrFunction public fun testFun(): kotlin.String
     IrExpressionBody
-      BLOCK type=kotlin.Nothing
+      BLOCK type=kotlin.Nothing hasResult=false isDesugared=false
         RETURN type=kotlin.Nothing
           LITERAL String type=kotlin.String value='OK'
   IrProperty public val testSimpleVal: kotlin.Int = 1 getter=null setter=null
@@ -20,4 +20,4 @@ IrFile /smoke.kt
       LITERAL Int type=kotlin.Int value='42'
   IrPropertySetter public fun <set-testVarWithAccessors>(/*0*/ v: kotlin.Int): kotlin.Unit property=testVarWithAccessors
     IrExpressionBody
-      BLOCK type=kotlin.Unit
+      BLOCK type=kotlin.Unit hasResult=false isDesugared=false