Check explicit type specification in "Might be const" inspection

So #KT-23303 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/MayBeConstantInspection.kt

@@ -9,6 +9,7 @@ import com.intellij.codeInspection.IntentionWrapper
 import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.codeInspection.ProblemsHolder
 import com.intellij.psi.PsiElementVisitor
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.inspections.MayBeConstantInspection.Status.*
@@ -44,10 +45,10 @@ class MayBeConstantInspection : AbstractKotlinInspection() {
                 MIGHT_BE_CONST_ERRONEOUS, JVM_FIELD_MIGHT_BE_CONST_ERRONEOUS -> return@propertyVisitor
                 MIGHT_BE_CONST, JVM_FIELD_MIGHT_BE_CONST -> {
                     holder.registerProblem(
-                            property.nameIdentifier ?: property,
+                        property.nameIdentifier ?: property,
-                            if (status == JVM_FIELD_MIGHT_BE_CONST) "'const' might be used instead of '@JvmField'" else "Might be 'const'",
+                        if (status == JVM_FIELD_MIGHT_BE_CONST) "'const' might be used instead of '@JvmField'" else "Might be 'const'",
-                            ProblemHighlightType.GENERIC_ERROR_OR_WARNING,
+                        ProblemHighlightType.GENERIC_ERROR_OR_WARNING,
-                            IntentionWrapper(AddConstModifierFix(property), property.containingFile)
+                        IntentionWrapper(AddConstModifierFix(property), property.containingFile)
                     )
                 }
             }
@@ -57,7 +58,8 @@ class MayBeConstantInspection : AbstractKotlinInspection() {
     companion object {
         fun KtProperty.getStatus(): Status {
             if (isLocal || isVar || getter != null ||
-                hasModifier(KtTokens.CONST_KEYWORD) || hasModifier(KtTokens.OVERRIDE_KEYWORD)) {
+                hasModifier(KtTokens.CONST_KEYWORD) || hasModifier(KtTokens.OVERRIDE_KEYWORD)
+            ) {
                 return NONE
             }
             if (!isTopLevel && containingClassOrObject !is KtObjectDeclaration) return NONE
@@ -66,13 +68,15 @@ class MayBeConstantInspection : AbstractKotlinInspection() {
             // For some reason constant evaluation does not work for property.analyze()
             val context = (initializer ?: this).analyze(BodyResolveMode.PARTIAL)
             val propertyDescriptor = context[BindingContext.DECLARATION_TO_DESCRIPTOR, this] as? VariableDescriptor ?: return NONE
+            val type = propertyDescriptor.type
+            if (!KotlinBuiltIns.isPrimitiveType(type) && !KotlinBuiltIns.isString(type)) return NONE
             val withJvmField = propertyDescriptor.hasJvmFieldAnnotation()
             if (annotationEntries.isNotEmpty() && !withJvmField) return NONE
 
             return when {
                 initializer != null -> {
                     val compileTimeConstant = ConstantExpressionEvaluator.getConstant(
-                            initializer, context
+                        initializer, context
                     ) ?: return NONE
                     val erroneousConstant = compileTimeConstant.usesNonConstValAsConstant
                     compileTimeConstant.toConstantValue(propertyDescriptor.type).takeIf {

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType.kt

@@ -0,0 +1 @@
+val <caret>foo: Int = 0

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType.kt.after

@@ -0,0 +1 @@
+const val foo: Int = 0

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType2.kt

@@ -0,0 +1 @@
+val <caret>foo: Boolean = true

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType2.kt.after

@@ -0,0 +1 @@
+const val foo: Boolean = true

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType3.kt

@@ -0,0 +1 @@
+val <caret>foo: String = ""

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType3.kt.after

@@ -0,0 +1 @@
+const val foo: String = ""

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType4.kt

@@ -0,0 +1,2 @@
+// PROBLEM: none
+val <caret>foo: Any = ""

idea/testData/inspectionsLocal/mayBeConstant/ecplicitType5.kt

@@ -0,0 +1,2 @@
+// PROBLEM: none
+val <caret>foo: Number = 0

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -2358,6 +2358,36 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("ecplicitType.kt")
+        public void testEcplicitType() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/mayBeConstant/ecplicitType.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("ecplicitType2.kt")
+        public void testEcplicitType2() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/mayBeConstant/ecplicitType2.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("ecplicitType3.kt")
+        public void testEcplicitType3() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/mayBeConstant/ecplicitType3.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("ecplicitType4.kt")
+        public void testEcplicitType4() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/mayBeConstant/ecplicitType4.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("ecplicitType5.kt")
+        public void testEcplicitType5() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/mayBeConstant/ecplicitType5.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("enum.kt")
         public void testEnum() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/mayBeConstant/enum.kt");