KT-17928 Support code folding for primary constructors

idea/src/org/jetbrains/kotlin/idea/KotlinFoldingBuilder.kt

@@ -82,7 +82,7 @@ class KotlinFoldingBuilder : CustomFoldingBuilder(), DumbAware {
         return type == KtNodeTypes.FUNCTION_LITERAL ||
                (type == KtNodeTypes.BLOCK && parentType != KtNodeTypes.FUNCTION_LITERAL) ||
                type == KtNodeTypes.CLASS_BODY || type == KtTokens.BLOCK_COMMENT || type == KDocTokens.KDOC ||
-               type == KtNodeTypes.STRING_TEMPLATE
+               type == KtNodeTypes.STRING_TEMPLATE || type == KtNodeTypes.PRIMARY_CONSTRUCTOR
     }
 
     private fun getRangeToFold(node: ASTNode): TextRange {
@@ -101,6 +101,7 @@ class KotlinFoldingBuilder : CustomFoldingBuilder(), DumbAware {
         node.elementType == KtTokens.BLOCK_COMMENT -> "/${getFirstLineOfComment(node)}.../"
         node.elementType == KDocTokens.KDOC -> "/**${getFirstLineOfComment(node)}...*/"
         node.elementType == KtNodeTypes.STRING_TEMPLATE -> "\"\"\"${getTrimmedFirstLineOfString(node).addSpaceIfNeeded()}...\"\"\""
+        node.elementType == KtNodeTypes.PRIMARY_CONSTRUCTOR -> "(...)"
         node.psi is KtImportList -> "..."
         else ->  "{...}"
     }

idea/testData/folding/checkCollapse/primaryConstructor.kt

@@ -0,0 +1,5 @@
+data class Test<fold text='(...)' expand='true'>(
+        val foo: Int,
+        val bar: Int,
+        val baz: Int
+)</fold>

idea/tests/org/jetbrains/kotlin/idea/folding/KotlinFoldingTestGenerated.java

@@ -136,5 +136,11 @@ public class KotlinFoldingTestGenerated extends AbstractKotlinFoldingTest {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/folding/checkCollapse/multilineStrings.kt");
             doSettingsFoldingTest(fileName);
         }
+
+        @TestMetadata("primaryConstructor.kt")
+        public void testPrimaryConstructor() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/folding/checkCollapse/primaryConstructor.kt");
+            doSettingsFoldingTest(fileName);
+        }
     }
 }