Fix for KT-12891: Allow to omit type in local delegated property declaration

#KT-12891 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/VariableTypeResolver.kt

@@ -16,7 +16,7 @@
 
 package org.jetbrains.kotlin.resolve
 
-import org.jetbrains.kotlin.descriptors.PropertyDescriptor
+import org.jetbrains.kotlin.descriptors.VariableDescriptorWithAccessors
 import org.jetbrains.kotlin.descriptors.impl.VariableDescriptorWithInitializerImpl
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.diagnostics.Errors.VARIABLE_WITH_NO_TYPE_NO_INITIALIZER
@@ -62,7 +62,7 @@ class VariableTypeResolver(
                 return type
             }
             !variable.hasInitializer() -> {
-                if (hasDelegate && variableDescriptor is PropertyDescriptor) {
+                if (hasDelegate && variableDescriptor is VariableDescriptorWithAccessors) {
                     val property = variable as KtProperty
                     if (property.hasDelegateExpression()) {
                         return DeferredType.createRecursionIntolerant(
@@ -131,18 +131,18 @@ class VariableTypeResolver(
 
     private fun resolveDelegatedPropertyType(
             property: KtProperty,
-            propertyDescriptor: PropertyDescriptor,
+            variableDescriptor: VariableDescriptorWithAccessors,
             scopeForInitializer: LexicalScope,
             delegateExpression: KtExpression,
             dataFlowInfo: DataFlowInfo,
             trace: BindingTrace
     ): KotlinType {
         val type = delegatedPropertyResolver.resolveDelegateExpression(
-                delegateExpression, property, propertyDescriptor, scopeForInitializer, trace, dataFlowInfo)
+                delegateExpression, property, variableDescriptor, scopeForInitializer, trace, dataFlowInfo)
 
-        val delegateFunctionsScope = ScopeUtils.makeScopeForDelegateConventionFunctions(scopeForInitializer, propertyDescriptor)
+        val delegateFunctionsScope = ScopeUtils.makeScopeForDelegateConventionFunctions(scopeForInitializer, variableDescriptor)
         val getterReturnType = delegatedPropertyResolver.getDelegatedPropertyGetMethodReturnType(
-                propertyDescriptor, delegateExpression, type, trace, delegateFunctionsScope, dataFlowInfo
+                variableDescriptor, delegateExpression, type, trace, delegateFunctionsScope, dataFlowInfo
         )
         if (getterReturnType != null) {
             return getterReturnType

compiler/testData/codegen/box/delegatedProperty/local/kt12891.kt

@@ -0,0 +1,5 @@
+//WITH_RUNTIME
+fun box(): String {
+    val x by lazy { "OK" }
+    return x
+}

compiler/testData/codegen/box/delegatedProperty/local/localValNoExplicitType.kt

@@ -0,0 +1,12 @@
+package foo
+
+import kotlin.reflect.KProperty
+
+class Delegate {
+    operator fun getValue(t: Any?, p: KProperty<*>): Int = 1
+}
+
+fun box(): String {
+    val prop by Delegate()
+    return if (prop == 1) "OK" else "fail"
+}

compiler/testData/codegen/box/delegatedProperty/local/localVarNoExplicitType.kt

@@ -0,0 +1,19 @@
+package foo
+
+import kotlin.reflect.KProperty
+
+class Delegate {
+    var inner = 1
+    operator fun getValue(t: Any?, p: KProperty<*>): Int = inner
+    operator fun setValue(t: Any?, p: KProperty<*>, i: Int) {
+        inner = i
+    }
+}
+
+fun box(): String {
+    var prop by Delegate()
+    if (prop != 1) return "fail get"
+    prop = 2
+    if (prop != 2) return "fail set"
+    return "OK"
+}

compiler/testData/codegen/script/localDelegatedPropertyNoExplicitType.kts

@@ -0,0 +1,14 @@
+import kotlin.reflect.KProperty
+
+class Delegate {
+    operator fun getValue(t: Any?, p: KProperty<*>): Int = 3
+}
+
+fun foo(): Int {
+    val prop by Delegate()
+    return prop
+}
+
+val x = foo()
+
+// expected: x: 3

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -5322,17 +5322,35 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("kt12891.kt")
+            public void testKt12891() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegatedProperty/local/kt12891.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("localVal.kt")
             public void testLocalVal() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegatedProperty/local/localVal.kt");
                 doTest(fileName);
             }
 
+            @TestMetadata("localValNoExplicitType.kt")
+            public void testLocalValNoExplicitType() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegatedProperty/local/localValNoExplicitType.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("localVar.kt")
             public void testLocalVar() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegatedProperty/local/localVar.kt");
                 doTest(fileName);
             }
+
+            @TestMetadata("localVarNoExplicitType.kt")
+            public void testLocalVarNoExplicitType() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/delegatedProperty/local/localVarNoExplicitType.kt");
+                doTest(fileName);
+            }
         }
     }
 

compiler/tests/org/jetbrains/kotlin/codegen/ScriptCodegenTestGenerated.java

@@ -71,6 +71,12 @@ public class ScriptCodegenTestGenerated extends AbstractScriptCodegenTest {
         doTest(fileName);
     }
 
+    @TestMetadata("localDelegatedPropertyNoExplicitType.kts")
+    public void testLocalDelegatedPropertyNoExplicitType() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/script/localDelegatedPropertyNoExplicitType.kts");
+        doTest(fileName);
+    }
+
     @TestMetadata("localFunction.kts")
     public void testLocalFunction() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/script/localFunction.kts");