FIR2IR: add two-statements block with iterator + while for 'for' loops

Before this commit we had two statements blocks for 'for' loops:
range variable declaration + iterator variable declaration + while loop.
However, BE requires a bit different loop structure to make lowerings
properly so in this commit iterator declaration & while loop were
extracted to separate block.

compiler/testData/ir/irText/expressions/breakContinueInLoopHeader.fir.txt

@@ -47,56 +47,58 @@ FILE fqName:<root> fileName:/breakContinueInLoopHeader.kt
       WHILE label=L origin=WHILE_LOOP
         condition: CONST Boolean type=kotlin.Boolean value=true
         body: BLOCK type=kotlin.Unit origin=WHILE_LOOP
-          VAR FOR_LOOP_ITERATOR name:tmp_2 type:kotlin.collections.Iterator<kotlin.String> [val]
-            CALL 'public abstract fun iterator (): kotlin.collections.Iterator<kotlin.String> [operator] declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=FOR_LOOP_ITERATOR
-              $this: BLOCK type=kotlin.collections.List<kotlin.String> origin=ELVIS
-                VAR IR_TEMPORARY_VARIABLE name:tmp_3 type:kotlin.collections.List<kotlin.String>? [val]
-                  GET_VAR 'ss: kotlin.collections.List<kotlin.String>? declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
-                WHEN type=kotlin.collections.List<kotlin.String> origin=ELVIS
-                  BRANCH
-                    if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
-                      arg0: GET_VAR 'val tmp_3: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
-                      arg1: CONST Null type=kotlin.Nothing? value=null
-                    then: CONTINUE label=L loop.label=L
-                  BRANCH
-                    if: CONST Boolean type=kotlin.Boolean value=true
-                    then: TYPE_OP type=kotlin.collections.List<kotlin.String> origin=IMPLICIT_CAST typeOperand=kotlin.collections.List<kotlin.String>
-                      GET_VAR 'val tmp_3: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
-          WHILE label=L2 origin=FOR_LOOP_INNER_WHILE
-            condition: CALL 'public abstract fun hasNext (): kotlin.Boolean [operator] declared in kotlin.collections.Iterator' type=kotlin.Boolean origin=FOR_LOOP_HAS_NEXT
-              $this: GET_VAR 'val tmp_2: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test3' type=kotlin.collections.Iterator<kotlin.String> origin=null
-            body: BLOCK type=kotlin.Unit origin=FOR_LOOP_INNER_WHILE
-              VAR FOR_LOOP_VARIABLE name:s type:kotlin.String [val]
-                CALL 'public abstract fun next (): T of kotlin.collections.Iterator [operator] declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
-                  $this: GET_VAR 'val tmp_2: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test3' type=kotlin.collections.Iterator<kotlin.String> origin=null
+          BLOCK type=kotlin.Unit origin=FOR_LOOP
+            VAR FOR_LOOP_ITERATOR name:tmp_2 type:kotlin.collections.Iterator<kotlin.String> [val]
+              CALL 'public abstract fun iterator (): kotlin.collections.Iterator<kotlin.String> [operator] declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=FOR_LOOP_ITERATOR
+                $this: BLOCK type=kotlin.collections.List<kotlin.String> origin=ELVIS
+                  VAR IR_TEMPORARY_VARIABLE name:tmp_3 type:kotlin.collections.List<kotlin.String>? [val]
+                    GET_VAR 'ss: kotlin.collections.List<kotlin.String>? declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
+                  WHEN type=kotlin.collections.List<kotlin.String> origin=ELVIS
+                    BRANCH
+                      if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
+                        arg0: GET_VAR 'val tmp_3: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
+                        arg1: CONST Null type=kotlin.Nothing? value=null
+                      then: CONTINUE label=L loop.label=L
+                    BRANCH
+                      if: CONST Boolean type=kotlin.Boolean value=true
+                      then: TYPE_OP type=kotlin.collections.List<kotlin.String> origin=IMPLICIT_CAST typeOperand=kotlin.collections.List<kotlin.String>
+                        GET_VAR 'val tmp_3: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
+            WHILE label=L2 origin=FOR_LOOP_INNER_WHILE
+              condition: CALL 'public abstract fun hasNext (): kotlin.Boolean [operator] declared in kotlin.collections.Iterator' type=kotlin.Boolean origin=FOR_LOOP_HAS_NEXT
+                $this: GET_VAR 'val tmp_2: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test3' type=kotlin.collections.Iterator<kotlin.String> origin=null
+              body: BLOCK type=kotlin.Unit origin=FOR_LOOP_INNER_WHILE
+                VAR FOR_LOOP_VARIABLE name:s type:kotlin.String [val]
+                  CALL 'public abstract fun next (): T of kotlin.collections.Iterator [operator] declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
+                    $this: GET_VAR 'val tmp_2: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test3' type=kotlin.collections.Iterator<kotlin.String> origin=null
   FUN name:test4 visibility:public modality:FINAL <> (ss:kotlin.collections.List<kotlin.String>?) returnType:kotlin.Unit
     VALUE_PARAMETER name:ss index:0 type:kotlin.collections.List<kotlin.String>?
     BLOCK_BODY
       WHILE label=L origin=WHILE_LOOP
         condition: CONST Boolean type=kotlin.Boolean value=true
         body: BLOCK type=kotlin.Unit origin=WHILE_LOOP
-          VAR FOR_LOOP_ITERATOR name:tmp_4 type:kotlin.collections.Iterator<kotlin.String> [val]
-            CALL 'public abstract fun iterator (): kotlin.collections.Iterator<kotlin.String> [operator] declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=FOR_LOOP_ITERATOR
-              $this: BLOCK type=kotlin.collections.List<kotlin.String> origin=ELVIS
-                VAR IR_TEMPORARY_VARIABLE name:tmp_5 type:kotlin.collections.List<kotlin.String>? [val]
-                  GET_VAR 'ss: kotlin.collections.List<kotlin.String>? declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
-                WHEN type=kotlin.collections.List<kotlin.String> origin=ELVIS
-                  BRANCH
-                    if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
-                      arg0: GET_VAR 'val tmp_5: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
-                      arg1: CONST Null type=kotlin.Nothing? value=null
-                    then: BREAK label=L loop.label=L
-                  BRANCH
-                    if: CONST Boolean type=kotlin.Boolean value=true
-                    then: TYPE_OP type=kotlin.collections.List<kotlin.String> origin=IMPLICIT_CAST typeOperand=kotlin.collections.List<kotlin.String>
-                      GET_VAR 'val tmp_5: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
-          WHILE label=L2 origin=FOR_LOOP_INNER_WHILE
-            condition: CALL 'public abstract fun hasNext (): kotlin.Boolean [operator] declared in kotlin.collections.Iterator' type=kotlin.Boolean origin=FOR_LOOP_HAS_NEXT
-              $this: GET_VAR 'val tmp_4: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test4' type=kotlin.collections.Iterator<kotlin.String> origin=null
-            body: BLOCK type=kotlin.Unit origin=FOR_LOOP_INNER_WHILE
-              VAR FOR_LOOP_VARIABLE name:s type:kotlin.String [val]
-                CALL 'public abstract fun next (): T of kotlin.collections.Iterator [operator] declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
-                  $this: GET_VAR 'val tmp_4: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test4' type=kotlin.collections.Iterator<kotlin.String> origin=null
+          BLOCK type=kotlin.Unit origin=FOR_LOOP
+            VAR FOR_LOOP_ITERATOR name:tmp_4 type:kotlin.collections.Iterator<kotlin.String> [val]
+              CALL 'public abstract fun iterator (): kotlin.collections.Iterator<kotlin.String> [operator] declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=FOR_LOOP_ITERATOR
+                $this: BLOCK type=kotlin.collections.List<kotlin.String> origin=ELVIS
+                  VAR IR_TEMPORARY_VARIABLE name:tmp_5 type:kotlin.collections.List<kotlin.String>? [val]
+                    GET_VAR 'ss: kotlin.collections.List<kotlin.String>? declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
+                  WHEN type=kotlin.collections.List<kotlin.String> origin=ELVIS
+                    BRANCH
+                      if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
+                        arg0: GET_VAR 'val tmp_5: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
+                        arg1: CONST Null type=kotlin.Nothing? value=null
+                      then: BREAK label=L loop.label=L
+                    BRANCH
+                      if: CONST Boolean type=kotlin.Boolean value=true
+                      then: TYPE_OP type=kotlin.collections.List<kotlin.String> origin=IMPLICIT_CAST typeOperand=kotlin.collections.List<kotlin.String>
+                        GET_VAR 'val tmp_5: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
+            WHILE label=L2 origin=FOR_LOOP_INNER_WHILE
+              condition: CALL 'public abstract fun hasNext (): kotlin.Boolean [operator] declared in kotlin.collections.Iterator' type=kotlin.Boolean origin=FOR_LOOP_HAS_NEXT
+                $this: GET_VAR 'val tmp_4: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test4' type=kotlin.collections.Iterator<kotlin.String> origin=null
+              body: BLOCK type=kotlin.Unit origin=FOR_LOOP_INNER_WHILE
+                VAR FOR_LOOP_VARIABLE name:s type:kotlin.String [val]
+                  CALL 'public abstract fun next (): T of kotlin.collections.Iterator [operator] declared in kotlin.collections.Iterator' type=kotlin.String origin=FOR_LOOP_NEXT
+                    $this: GET_VAR 'val tmp_4: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test4' type=kotlin.collections.Iterator<kotlin.String> origin=null
   FUN name:test5 visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
       VAR name:i type:kotlin.Int [var]