Introduce IrFunctionExpression IR element

Use it to represent proper function expressions (lambdas and anonymous
functions).

compiler/testData/ir/irText/declarations/annotations/delegateFieldWithAnnotations.txt

@@ -22,12 +22,11 @@ FILE fqName:<root> fileName:/delegateFieldWithAnnotations.kt
       EXPRESSION_BODY
         CALL 'public final fun lazy <T> (initializer: kotlin.Function0<T of kotlin.lazy>): kotlin.Lazy<T of kotlin.lazy> declared in kotlin' type=kotlin.Lazy<kotlin.Int> origin=null
           <T>: kotlin.Int
-          initializer: BLOCK type=kotlin.Function0<kotlin.Int> origin=LAMBDA
+          initializer: FUN_EXPR type=kotlin.Function0<kotlin.Int>
             FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Int 
               BLOCK_BODY
                 RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Int declared in <root>.test1$delegate'
                   CONST Int type=kotlin.Int value=42
-            FUNCTION_REFERENCE 'local final fun <anonymous> (): kotlin.Int declared in <root>.test1$delegate' type=kotlin.Function0<kotlin.Int> origin=LAMBDA
     FUN DELEGATED_PROPERTY_ACCESSOR name:<get-test1> visibility:public modality:FINAL <> () returnType:kotlin.Int 
       correspondingProperty: PROPERTY name:test1 visibility:public modality:FINAL [delegated,val] 
       BLOCK_BODY

compiler/testData/ir/irText/declarations/annotations/localDelegatedPropertiesWithAnnotations.txt

@@ -36,12 +36,11 @@ FILE fqName:<root> fileName:/localDelegatedPropertiesWithAnnotations.kt
         VAR DELEGATE name:test$delegate type:kotlin.Lazy<kotlin.Int> [val] 
           CALL 'public final fun lazy <T> (initializer: kotlin.Function0<T of kotlin.lazy>): kotlin.Lazy<T of kotlin.lazy> declared in kotlin' type=kotlin.Lazy<kotlin.Int> origin=null
             <T>: kotlin.Int
-            initializer: BLOCK type=kotlin.Function0<kotlin.Int> origin=LAMBDA
+            initializer: FUN_EXPR type=kotlin.Function0<kotlin.Int>
               FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Int 
                 BLOCK_BODY
                   RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Int declared in <root>.foo'
                     CONST Int type=kotlin.Int value=42
-              FUNCTION_REFERENCE 'local final fun <anonymous> (): kotlin.Int declared in <root>.foo' type=kotlin.Function0<kotlin.Int> origin=LAMBDA
         FUN DELEGATED_PROPERTY_ACCESSOR name:<get-test> visibility:local modality:FINAL <> () returnType:kotlin.Int 
           BLOCK_BODY
             RETURN type=kotlin.Nothing from='local final fun <get-test> (): kotlin.Int declared in <root>.foo'

compiler/testData/ir/irText/declarations/classLevelProperties.txt

@@ -96,12 +96,11 @@ FILE fqName:<root> fileName:/classLevelProperties.kt
         EXPRESSION_BODY
           CALL 'public final fun lazy <T> (initializer: kotlin.Function0<T of kotlin.lazy>): kotlin.Lazy<T of kotlin.lazy> declared in kotlin' type=kotlin.Lazy<kotlin.Int> origin=null
             <T>: kotlin.Int
-            initializer: BLOCK type=kotlin.Function0<kotlin.Int> origin=LAMBDA
+            initializer: FUN_EXPR type=kotlin.Function0<kotlin.Int>
               FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Int 
                 BLOCK_BODY
                   RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Int declared in <root>.C.test7$delegate'
                     CONST Int type=kotlin.Int value=42
-              FUNCTION_REFERENCE 'local final fun <anonymous> (): kotlin.Int declared in <root>.C.test7$delegate' type=kotlin.Function0<kotlin.Int> origin=LAMBDA
       FUN DELEGATED_PROPERTY_ACCESSOR name:<get-test7> visibility:public modality:FINAL <> ($this:<root>.C) returnType:kotlin.Int 
         correspondingProperty: PROPERTY name:test7 visibility:public modality:FINAL [delegated,val] 
         $this: VALUE_PARAMETER name:<this> type:<root>.C 

compiler/testData/ir/irText/declarations/delegatedProperties.txt

@@ -4,12 +4,11 @@ FILE fqName:<root> fileName:/delegatedProperties.kt
       EXPRESSION_BODY
         CALL 'public final fun lazy <T> (initializer: kotlin.Function0<T of kotlin.lazy>): kotlin.Lazy<T of kotlin.lazy> declared in kotlin' type=kotlin.Lazy<kotlin.Int> origin=null
           <T>: kotlin.Int
-          initializer: BLOCK type=kotlin.Function0<kotlin.Int> origin=LAMBDA
+          initializer: FUN_EXPR type=kotlin.Function0<kotlin.Int>
             FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Int 
               BLOCK_BODY
                 RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Int declared in <root>.test1$delegate'
                   CONST Int type=kotlin.Int value=42
-            FUNCTION_REFERENCE 'local final fun <anonymous> (): kotlin.Int declared in <root>.test1$delegate' type=kotlin.Function0<kotlin.Int> origin=LAMBDA
     FUN DELEGATED_PROPERTY_ACCESSOR name:<get-test1> visibility:public modality:FINAL <> () returnType:kotlin.Int 
       correspondingProperty: PROPERTY name:test1 visibility:public modality:FINAL [delegated,val] 
       BLOCK_BODY
@@ -42,12 +41,11 @@ FILE fqName:<root> fileName:/delegatedProperties.kt
         EXPRESSION_BODY
           CALL 'public final fun lazy <T> (initializer: kotlin.Function0<T of kotlin.lazy>): kotlin.Lazy<T of kotlin.lazy> declared in kotlin' type=kotlin.Lazy<kotlin.Int> origin=null
             <T>: kotlin.Int
-            initializer: BLOCK type=kotlin.Function0<kotlin.Int> origin=LAMBDA
+            initializer: FUN_EXPR type=kotlin.Function0<kotlin.Int>
               FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Int 
                 BLOCK_BODY
                   RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Int declared in <root>.C.test2$delegate'
                     CONST Int type=kotlin.Int value=42
-              FUNCTION_REFERENCE 'local final fun <anonymous> (): kotlin.Int declared in <root>.C.test2$delegate' type=kotlin.Function0<kotlin.Int> origin=LAMBDA
       FUN DELEGATED_PROPERTY_ACCESSOR name:<get-test2> visibility:public modality:FINAL <> ($this:<root>.C) returnType:kotlin.Int 
         correspondingProperty: PROPERTY name:test2 visibility:public modality:FINAL [delegated,val] 
         $this: VALUE_PARAMETER name:<this> type:<root>.C 

compiler/testData/ir/irText/declarations/localDelegatedProperties.txt

@@ -5,12 +5,11 @@ FILE fqName:<root> fileName:/localDelegatedProperties.kt
         VAR DELEGATE name:x$delegate type:kotlin.Lazy<kotlin.Int> [val] 
           CALL 'public final fun lazy <T> (initializer: kotlin.Function0<T of kotlin.lazy>): kotlin.Lazy<T of kotlin.lazy> declared in kotlin' type=kotlin.Lazy<kotlin.Int> origin=null
             <T>: kotlin.Int
-            initializer: BLOCK type=kotlin.Function0<kotlin.Int> origin=LAMBDA
+            initializer: FUN_EXPR type=kotlin.Function0<kotlin.Int>
               FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Int 
                 BLOCK_BODY
                   RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Int declared in <root>.test1'
                     CONST Int type=kotlin.Int value=42
-              FUNCTION_REFERENCE 'local final fun <anonymous> (): kotlin.Int declared in <root>.test1' type=kotlin.Function0<kotlin.Int> origin=LAMBDA
         FUN DELEGATED_PROPERTY_ACCESSOR name:<get-x> visibility:local modality:FINAL <> () returnType:kotlin.Int 
           BLOCK_BODY
             RETURN type=kotlin.Nothing from='local final fun <get-x> (): kotlin.Int declared in <root>.test1'

compiler/testData/ir/irText/declarations/packageLevelProperties.txt

@@ -73,12 +73,11 @@ FILE fqName:<root> fileName:/packageLevelProperties.kt
       EXPRESSION_BODY
         CALL 'public final fun lazy <T> (initializer: kotlin.Function0<T of kotlin.lazy>): kotlin.Lazy<T of kotlin.lazy> declared in kotlin' type=kotlin.Lazy<kotlin.Int> origin=null
           <T>: kotlin.Int
-          initializer: BLOCK type=kotlin.Function0<kotlin.Int> origin=LAMBDA
+          initializer: FUN_EXPR type=kotlin.Function0<kotlin.Int>
             FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Int 
               BLOCK_BODY
                 RETURN type=kotlin.Nothing from='local final fun <anonymous> (): kotlin.Int declared in <root>.test7$delegate'
                   CONST Int type=kotlin.Int value=42
-            FUNCTION_REFERENCE 'local final fun <anonymous> (): kotlin.Int declared in <root>.test7$delegate' type=kotlin.Function0<kotlin.Int> origin=LAMBDA
     FUN DELEGATED_PROPERTY_ACCESSOR name:<get-test7> visibility:public modality:FINAL <> () returnType:kotlin.Int 
       correspondingProperty: PROPERTY name:test7 visibility:public modality:FINAL [delegated,val] 
       BLOCK_BODY

compiler/testData/ir/irText/declarations/parameters/lambdas.txt

@@ -2,13 +2,12 @@ FILE fqName:<root> fileName:/lambdas.kt
   PROPERTY name:test1 visibility:public modality:FINAL [val] 
     FIELD PROPERTY_BACKING_FIELD name:test1 type:kotlin.Function1<kotlin.String, kotlin.String> visibility:public [final,static] 
       EXPRESSION_BODY
-        BLOCK type=kotlin.Function1<kotlin.String, kotlin.String> origin=LAMBDA
+        FUN_EXPR type=kotlin.Function1<kotlin.String, kotlin.String>
           FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> (it:kotlin.String) returnType:kotlin.String 
             VALUE_PARAMETER name:it index:0 type:kotlin.String 
             BLOCK_BODY
               RETURN type=kotlin.Nothing from='local final fun <anonymous> (it: kotlin.String): kotlin.String declared in <root>.test1'
                 GET_VAR 'it: kotlin.String declared in <root>.test1.<anonymous>' type=kotlin.String origin=null
-          FUNCTION_REFERENCE 'local final fun <anonymous> (it: kotlin.String): kotlin.String declared in <root>.test1' type=kotlin.Function1<kotlin.String, kotlin.String> origin=LAMBDA
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test1> visibility:public modality:FINAL <> () returnType:kotlin.Function1<kotlin.String, kotlin.String> 
       correspondingProperty: PROPERTY name:test1 visibility:public modality:FINAL [val] 
       BLOCK_BODY
@@ -17,7 +16,7 @@ FILE fqName:<root> fileName:/lambdas.kt
   PROPERTY name:test2 visibility:public modality:FINAL [val] 
     FIELD PROPERTY_BACKING_FIELD name:test2 type:@[ExtensionFunctionType] kotlin.Function2<kotlin.Any, kotlin.Any, kotlin.Any> visibility:public [final,static] 
       EXPRESSION_BODY
-        BLOCK type=@[ExtensionFunctionType] kotlin.Function2<kotlin.Any, kotlin.Any, kotlin.Int> origin=LAMBDA
+        FUN_EXPR type=@[ExtensionFunctionType] kotlin.Function2<kotlin.Any, kotlin.Any, kotlin.Int>
           FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> ($receiver:kotlin.Any, it:kotlin.Any) returnType:kotlin.Int 
             $receiver: VALUE_PARAMETER name:<this> type:kotlin.Any 
             VALUE_PARAMETER name:it index:0 type:kotlin.Any 
@@ -25,7 +24,6 @@ FILE fqName:<root> fileName:/lambdas.kt
               RETURN type=kotlin.Nothing from='local final fun <anonymous> (it: kotlin.Any): kotlin.Int declared in <root>.test2'
                 CALL 'public open fun hashCode (): kotlin.Int declared in kotlin.Any' type=kotlin.Int origin=null
                   $this: GET_VAR 'it: kotlin.Any declared in <root>.test2.<anonymous>' type=kotlin.Any origin=null
-          FUNCTION_REFERENCE 'local final fun <anonymous> (it: kotlin.Any): kotlin.Int declared in <root>.test2' type=@[ExtensionFunctionType] kotlin.Function2<kotlin.Any, kotlin.Any, kotlin.Int> origin=LAMBDA
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test2> visibility:public modality:FINAL <> () returnType:@[ExtensionFunctionType] kotlin.Function2<kotlin.Any, kotlin.Any, kotlin.Any> 
       correspondingProperty: PROPERTY name:test2 visibility:public modality:FINAL [val] 
       BLOCK_BODY
@@ -34,14 +32,13 @@ FILE fqName:<root> fileName:/lambdas.kt
   PROPERTY name:test3 visibility:public modality:FINAL [val] 
     FIELD PROPERTY_BACKING_FIELD name:test3 type:kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> visibility:public [final,static] 
       EXPRESSION_BODY
-        BLOCK type=kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> origin=LAMBDA
+        FUN_EXPR type=kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit>
           FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> (i:kotlin.Int, j:kotlin.Int) returnType:kotlin.Unit 
             VALUE_PARAMETER name:i index:0 type:kotlin.Int 
             VALUE_PARAMETER name:j index:1 type:kotlin.Int 
             BLOCK_BODY
               RETURN type=kotlin.Nothing from='local final fun <anonymous> (i: kotlin.Int, j: kotlin.Int): kotlin.Unit declared in <root>.test3'
                 GET_OBJECT 'CLASS IR_EXTERNAL_DECLARATION_STUB OBJECT name:Unit modality:FINAL visibility:public superTypes:[kotlin.Any]' type=kotlin.Unit
-          FUNCTION_REFERENCE 'local final fun <anonymous> (i: kotlin.Int, j: kotlin.Int): kotlin.Unit declared in <root>.test3' type=kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> origin=LAMBDA
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test3> visibility:public modality:FINAL <> () returnType:kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> 
       correspondingProperty: PROPERTY name:test3 visibility:public modality:FINAL [val] 
       BLOCK_BODY
@@ -50,12 +47,11 @@ FILE fqName:<root> fileName:/lambdas.kt
   PROPERTY name:test4 visibility:public modality:FINAL [val] 
     FIELD PROPERTY_BACKING_FIELD name:test4 type:kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> visibility:public [final,static] 
       EXPRESSION_BODY
-        BLOCK type=kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> origin=ANONYMOUS_FUNCTION
+        FUN_EXPR type=kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit>
           FUN name:<no name provided> visibility:local modality:FINAL <> (i:kotlin.Int, j:kotlin.Int) returnType:kotlin.Unit 
             VALUE_PARAMETER name:i index:0 type:kotlin.Int 
             VALUE_PARAMETER name:j index:1 type:kotlin.Int 
             BLOCK_BODY
-          FUNCTION_REFERENCE 'local final fun <no name provided> (i: kotlin.Int, j: kotlin.Int): kotlin.Unit declared in <root>.test4' type=kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> origin=ANONYMOUS_FUNCTION
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test4> visibility:public modality:FINAL <> () returnType:kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Unit> 
       correspondingProperty: PROPERTY name:test4 visibility:public modality:FINAL [val] 
       BLOCK_BODY