Coerce loop body to Unit.

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/transformations/InsertImplicitCasts.kt

@@ -145,6 +145,8 @@ class InsertImplicitCasts(val builtIns: KotlinBuiltIns): IrElementTransformerVoi
 
         loop.condition = loop.condition.cast(builtIns.booleanType)
 
+        loop.body = loop.body?.coerceToUnit(builtIns.unitType)
+
         return loop
     }
 

compiler/testData/ir/irText/regressions/coercionInLoop.kt

@@ -0,0 +1,10 @@
+fun box(): String {
+    val a = DoubleArray(5)
+    val x = a.iterator()
+    var i = 0
+    while (x.hasNext()) {
+        if (a[i] != x.next()) return "Fail $i"
+        i++
+    }
+    return "OK"
+}

compiler/testData/ir/irText/regressions/coercionInLoop.txt

@@ -0,0 +1,37 @@
+FILE /coercionInLoop.kt
+  FUN public fun box(): kotlin.String
+    BLOCK_BODY
+      VAR val a: kotlin.DoubleArray
+        CALL 'constructor DoubleArray(Int)' type=kotlin.DoubleArray origin=null
+          size: CONST Int type=kotlin.Int value='5'
+      VAR val x: kotlin.collections.DoubleIterator
+        CALL 'iterator(): DoubleIterator' type=kotlin.collections.DoubleIterator origin=null
+          $this: GET_VAR 'a: DoubleArray' type=kotlin.DoubleArray origin=null
+      VAR var i: kotlin.Int
+        CONST Int type=kotlin.Int value='0'
+      WHILE label=null origin=WHILE_LOOP
+        condition: CALL 'hasNext(): Boolean' type=kotlin.Boolean origin=null
+          $this: GET_VAR 'x: DoubleIterator' type=kotlin.collections.DoubleIterator origin=null
+        body: TYPE_OP origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+          BLOCK type=kotlin.Int origin=null
+            WHEN type=kotlin.Unit origin=IF
+              if: CALL 'NOT(Boolean): Boolean' type=kotlin.Boolean origin=EXCLEQ
+                arg0: CALL 'EQEQ(Any?, Any?): Boolean' type=kotlin.Boolean origin=EXCLEQ
+                  arg0: CALL 'get(Int): Double' type=kotlin.Double origin=GET_ARRAY_ELEMENT
+                    $this: GET_VAR 'a: DoubleArray' type=kotlin.DoubleArray origin=null
+                    index: GET_VAR 'i: Int' type=kotlin.Int origin=null
+                  arg1: CALL 'next(): Double' type=kotlin.Double origin=null
+                    $this: GET_VAR 'x: DoubleIterator' type=kotlin.collections.DoubleIterator origin=null
+              then: RETURN type=kotlin.Nothing from='box(): String'
+                STRING_CONCATENATION type=kotlin.String
+                  CONST String type=kotlin.String value='Fail '
+                  GET_VAR 'i: Int' type=kotlin.Int origin=null
+            BLOCK type=kotlin.Int origin=POSTFIX_INCR
+              VAR IR_TEMPORARY_VARIABLE val tmp0: kotlin.Int
+                GET_VAR 'i: Int' type=kotlin.Int origin=POSTFIX_INCR
+              SET_VAR 'i: Int' type=kotlin.Unit origin=POSTFIX_INCR
+                CALL 'inc(): Int' type=kotlin.Int origin=POSTFIX_INCR
+                  $this: GET_VAR 'tmp0: Int' type=kotlin.Int origin=null
+              GET_VAR 'tmp0: Int' type=kotlin.Int origin=null
+      RETURN type=kotlin.Nothing from='box(): String'
+        CONST String type=kotlin.String value='OK'

compiler/tests/org/jetbrains/kotlin/ir/IrTextTestCaseGenerated.java

@@ -715,4 +715,19 @@ public class IrTextTestCaseGenerated extends AbstractIrTextTestCase {
             doTest(fileName);
         }
     }
+
+    @TestMetadata("compiler/testData/ir/irText/regressions")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class Regressions extends AbstractIrTextTestCase {
+        public void testAllFilesPresentInRegressions() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/ir/irText/regressions"), Pattern.compile("^(.+)\\.kt$"), true);
+        }
+
+        @TestMetadata("coercionInLoop.kt")
+        public void testCoercionInLoop() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/ir/irText/regressions/coercionInLoop.kt");
+            doTest(fileName);
+        }
+    }
 }