Don't ruin indentation for comments inside expression declarations (KT-23295)

#KT-23295 Fixed

compiler/psi/src/org/jetbrains/kotlin/psi/KtDestructuringDeclaration.java

@@ -29,7 +29,7 @@ import java.util.List;
 
 import static org.jetbrains.kotlin.lexer.KtTokens.*;
 
-public class KtDestructuringDeclaration extends KtDeclarationImpl implements KtValVarKeywordOwner {
+public class KtDestructuringDeclaration extends KtDeclarationImpl implements KtValVarKeywordOwner, KtDeclarationWithInitializer {
     public KtDestructuringDeclaration(@NotNull ASTNode node) {
         super(node);
     }
@@ -45,6 +45,7 @@ public class KtDestructuringDeclaration extends KtDeclarationImpl implements KtV
     }
 
     @Nullable
+    @Override
     public KtExpression getInitializer() {
         ASTNode eqNode = getNode().findChildByType(EQ);
         if (eqNode == null) {
@@ -53,6 +54,11 @@ public class KtDestructuringDeclaration extends KtDeclarationImpl implements KtV
         return PsiTreeUtil.getNextSiblingOfType(eqNode.getPsi(), KtExpression.class);
     }
 
+    @Override
+    public boolean hasInitializer() {
+        return getInitializer() != null;
+    }
+
     public boolean isVar() {
         return getNode().findChildByType(KtTokens.VAR_KEYWORD) != null;
     }

idea/formatter/src/org/jetbrains/kotlin/idea/formatter/KotlinCommonBlock.kt

@@ -26,10 +26,7 @@ import org.jetbrains.kotlin.kdoc.parser.KDocElementTypes
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.lexer.KtTokens.*
 import org.jetbrains.kotlin.psi.*
-import org.jetbrains.kotlin.psi.psiUtil.children
-import org.jetbrains.kotlin.psi.psiUtil.leaves
-import org.jetbrains.kotlin.psi.psiUtil.parents
-import org.jetbrains.kotlin.psi.psiUtil.siblings
+import org.jetbrains.kotlin.psi.psiUtil.*
 
 private val QUALIFIED_OPERATION = TokenSet.create(DOT, SAFE_ACCESS)
 private val QUALIFIED_EXPRESSIONS = TokenSet.create(KtNodeTypes.DOT_QUALIFIED_EXPRESSION, KtNodeTypes.SAFE_ACCESS_EXPRESSION)
@@ -695,7 +692,19 @@ private val INDENT_RULES = arrayOf(
     strategy("Expression body")
         .within(KtNodeTypes.FUN)
         .forElement {
-            it.psi is KtExpression && it.psi !is KtBlockExpression
+            (it.psi is KtExpression && it.psi !is KtBlockExpression)
+        }
+        .continuationIf(KotlinCodeStyleSettings::CONTINUATION_INDENT_FOR_EXPRESSION_BODIES, indentFirst = true),
+
+    strategy("Line comment at expression body position")
+        .forElement { node ->
+            val psi = node.psi
+            val parent = psi.parent
+            if (psi is PsiComment && parent is KtDeclarationWithInitializer) {
+                psi.getNextSiblingIgnoringWhitespace() == parent.initializer
+            } else {
+                false
+            }
         }
         .continuationIf(KotlinCodeStyleSettings::CONTINUATION_INDENT_FOR_EXPRESSION_BODIES, indentFirst = true),
 

idea/testData/formatter/CommentInExpressionBodies.after.kt

@@ -0,0 +1,17 @@
+fun foo() =
+        // comment
+        1
+
+val some =
+        // Comment
+        2
+
+fun some() {
+    val (a, b) =
+            // Some
+            1 to 3
+}
+
+fun nice() =
+        /* Ha! */
+        2

idea/testData/formatter/CommentInExpressionBodies.kt

@@ -0,0 +1,17 @@
+fun foo() =
+  // comment
+  1
+
+val some =
+                            // Comment
+                            2
+
+fun some() {
+    val (a, b) =
+    // Some
+    1 to 3
+}
+
+fun nice() =
+ /* Ha! */
+2

idea/tests/org/jetbrains/kotlin/formatter/FormatterTestGenerated.java

@@ -166,6 +166,11 @@ public class FormatterTestGenerated extends AbstractFormatterTest {
             runTest("idea/testData/formatter/ColonSpaces.after.kt");
         }
 
+        @TestMetadata("CommentInExpressionBodies.after.kt")
+        public void testCommentInExpressionBodies() throws Exception {
+            runTest("idea/testData/formatter/CommentInExpressionBodies.after.kt");
+        }
+
         @TestMetadata("CommentInFunctionLiteral.after.kt")
         public void testCommentInFunctionLiteral() throws Exception {
             runTest("idea/testData/formatter/CommentInFunctionLiteral.after.kt");