Remove unchecked cast for self types. Add self type scope to BodyResolveContext

Author: maxim092001

compiler/fir/analysis-tests/testData/resolve/cfg/selfTypes.kt

@@ -8,30 +8,30 @@ class JustSelfAnnotation {
 @Self
 class ReturnType {
     fun returnTypeWithVal(): Self {
-        val res: Self  = this <!UNCHECKED_CAST!>as Self<!>
+        val res: Self  = this as Self
         return res
     }
 }
 
 @Self
 class ReturnTypeWithTypeParameter<T> {
     fun returnType(): Self {
-        return this <!UNCHECKED_CAST!>as Self<!>
+        return this as Self
     }
 }
 
 @Self
 class ReturnTypeWithTypeParameters<T, A, F> {
     fun returnType(): Self {
-        return this <!UNCHECKED_CAST!>as Self<!>
+        return this as Self
     }
 }
 
 class InnerClass {
     @Self
     inner class Inner {
         fun returnType(): Self {
-            return this <!UNCHECKED_CAST!>as Self<!>
+            return this as Self
         }
     }
 }
@@ -40,7 +40,7 @@ class StaticClass {
     @Self
     class Static {
         fun returnType(): Self {
-            return this <!UNCHECKED_CAST!>as Self<!>
+            return this as Self
         }
     }
 }
@@ -54,7 +54,7 @@ class InnerSelfClass {
     }
 
     fun returnType(): Self {
-        return this <!UNCHECKED_CAST!>as Self<!>
+        return this as Self
     }
 
     fun returnSelfClassType(): InnerSelfClass.Self {
@@ -68,7 +68,7 @@ class TypeAliasSelf {
     typealias Self = String
 
     fun returnType(): Self {
-        return this <!UNCHECKED_CAST!>as Self<!>
+        return this as Self
     }
 
     fun returnTypealias(): TypeAliasSelf.Self {

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirCastOperatorsChecker.kt

@@ -17,6 +17,8 @@ import org.jetbrains.kotlin.fir.expressions.FirOperation
 import org.jetbrains.kotlin.fir.expressions.FirTypeOperatorCall
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.types.coneType
+import org.jetbrains.kotlin.fir.types.toSymbol
+import org.jetbrains.kotlin.name.SpecialNames
 
 object FirCastOperatorsChecker : FirTypeOperatorCallChecker() {
     override fun check(expression: FirTypeOperatorCall, context: CheckerContext, reporter: DiagnosticReporter) {
@@ -38,7 +40,12 @@ object FirCastOperatorsChecker : FirTypeOperatorCallChecker() {
             } else if (castType == CastingType.Always) {
                 reporter.reportOn(expression.source, FirErrors.USELESS_CAST, context)
             } else if (isCastErased(actualType, targetType, context)) {
-                reporter.reportOn(expression.source, FirErrors.UNCHECKED_CAST, actualType, targetType, context)
+
+                val isTargetTypeSelf = targetType.toSymbol(session)?.toLookupTag()?.name.let { it == SpecialNames.SELF_TYPE }
+                val isTargetTypeTypeArg = actualType.typeArguments.contains(targetType)
+
+                if (!(isTargetTypeTypeArg && isTargetTypeSelf))
+                    reporter.reportOn(expression.source, FirErrors.UNCHECKED_CAST, actualType, targetType, context)
             }
         } else if (expression.operation == FirOperation.IS) {
             if (isCastErased(actualType, targetType, context)) {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/BodyResolveContext.kt

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.fir.scopes.FirScope
 import org.jetbrains.kotlin.fir.scopes.createImportingScopes
 import org.jetbrains.kotlin.fir.scopes.impl.FirLocalScope
 import org.jetbrains.kotlin.fir.scopes.impl.FirMemberTypeParameterScope
+import org.jetbrains.kotlin.fir.scopes.impl.FirSelfTypeScope
 import org.jetbrains.kotlin.fir.scopes.impl.FirWhenSubjectImportingScope
 import org.jetbrains.kotlin.fir.symbols.impl.FirAnonymousFunctionSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
@@ -445,12 +446,15 @@ class BodyResolveContext(
             .addNonLocalScopeIfNotNull(towerElementsForClass.staticScope)
 
         val typeParameterScope = (owner as? FirRegularClass)?.typeParameterScope()
+        val selfTypeScope: FirSelfTypeScope? =
+            owner.annotations.find { it.fqName(holder.session)?.asString() == "kotlin.Self" }?.let { FirSelfTypeScope(owner) }
 
         val forMembersResolution =
             staticsAndCompanion
                 .addReceiver(labelName, towerElementsForClass.thisReceiver)
                 .addContextReceiverGroup(towerElementsForClass.contextReceivers)
                 .addNonLocalScopeIfNotNull(typeParameterScope)
+                .addNonLocalScopeIfNotNull(selfTypeScope)
 
         val scopeForConstructorHeader =
             staticsAndCompanion.addNonLocalScopeIfNotNull(typeParameterScope)

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirBodyResolveTransformer.kt

@@ -68,19 +68,10 @@ open class FirBodyResolveTransformer(
         } else {
 
             typeResolverTransformer.withFile(context.file) {
-
-                val selfAnnotation =
-                    context.topClassDeclaration?.annotations?.find { it.fqName(session)?.asString() == "kotlin.Self" }
-                val scopes =
-                    if (context.topClassDeclaration != null && selfAnnotation != null)
-                        listOf(FirSelfTypeScope(context.topClassDeclaration!!)) + components.createCurrentScopeList()
-                    else
-                        emptyList()
-
                 transformTypeRef(
                     typeRef,
                     ScopeClassDeclaration(
-                        scopes,
+                        components.createCurrentScopeList(),
                         context.containingClassDeclarations,
                         context.containers.lastOrNull { it is FirTypeParameterRefsOwner && it !is FirAnonymousFunction }
                     )