Introduce FunctionDescriptor.initialSignatureDescriptor

Mostly it's needed for backend to extract descriptor with initial signature

For example:
class A implements CharSequence {
        char charAt(int index) {}
}

We see `charAt` this method as `fun get(index: Int): Char`, but in backend it
matters what signature had this descriptor before.

compiler/backend/src/org/jetbrains/kotlin/codegen/state/JetTypeMapper.java

@@ -42,7 +42,6 @@ import org.jetbrains.kotlin.load.java.SpecialBuiltinMembers;
 import org.jetbrains.kotlin.load.java.descriptors.JavaCallableMemberDescriptor;
 import org.jetbrains.kotlin.load.java.descriptors.JavaClassDescriptor;
 import org.jetbrains.kotlin.load.java.lazy.descriptors.LazyJavaPackageScope;
-import org.jetbrains.kotlin.load.java.sources.JavaSourceElement;
 import org.jetbrains.kotlin.load.kotlin.incremental.IncrementalPackageFragmentProvider;
 import org.jetbrains.kotlin.load.kotlin.incremental.components.IncrementalCache;
 import org.jetbrains.kotlin.name.*;
@@ -955,15 +954,14 @@ public class JetTypeMapper {
 
     @NotNull
     public JvmMethodSignature mapSignature(@NotNull FunctionDescriptor f, @NotNull OwnerKind kind) {
-        if (f.getOriginal().getSource() instanceof JavaSourceElement) {
+        if (f.getInitialSignatureDescriptor() != null && f != f.getInitialSignatureDescriptor()) {
-            FunctionDescriptor overridden = SpecialBuiltinMembers.<FunctionDescriptor>getOverriddenBuiltinWithDifferentJvmDescriptor(f);
+            // Overrides of special builtin in Kotlin classes always have special signature
-            if (overridden != null
+            if (SpecialBuiltinMembers.getOverriddenBuiltinWithDifferentJvmDescriptor(f) == null ||
-                && !SpecialBuiltinMembers.hasRealKotlinSuperClassWithOverrideOf(
+                f.getContainingDeclaration().getOriginal() instanceof JavaClassDescriptor) {
-                    (ClassDescriptor) f.getContainingDeclaration(), overridden)
+                return mapSignature(f.getInitialSignatureDescriptor(), kind);
-            ) {
-                return mapSignature(overridden, kind, overridden.getValueParameters());
             }
         }
+
         if (f instanceof ConstructorDescriptor) {
             return mapSignature(f, kind, f.getOriginal().getValueParameters());
         }

compiler/frontend.java/src/org/jetbrains/kotlin/synthetic/SamAdapterFunctionsScope.kt

@@ -173,12 +173,14 @@ class SamAdapterFunctionsScope(storageManager: StorageManager) : BaseImportingSc
                 newExtensionReceiverParameterType: KotlinType?,
                 newReturnType: KotlinType,
                 name: Name?,
-                preserveSource: Boolean
+                preserveSource: Boolean,
+                signatureChange: Boolean
         ): FunctionDescriptor? {
             val descriptor = super.doSubstitute(
                     originalSubstitutor, newOwner, newModality, newVisibility,
                     newIsOperator, newIsInfix, newIsExternal, newIsInline, newIsTailrec, original,
-                    copyOverrides, kind, newValueParameterDescriptors, newExtensionReceiverParameterType, newReturnType, name, preserveSource)
+                    copyOverrides, kind, newValueParameterDescriptors, newExtensionReceiverParameterType, newReturnType, name,
+                    preserveSource, signatureChange)
                     as MyFunctionDescriptor? ?: return null
 
             if (original == null) {

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/descriptors/JavaMethodDescriptor.java

@@ -147,7 +147,7 @@ public class JavaMethodDescriptor extends SimpleFunctionDescriptorImpl implement
                 isOperator(), isInfix(), isExternal(), isInline(), isTailrec(), getOriginal(),
                 /* copyOverrides = */ true, getKind(),
                 enhancedValueParameters, enhancedReceiverType, enhancedReturnType,
-                null, false);
+                null, /* preserveSource */false, /* signatureChange = */ false);
 
         assert enhancedMethod != null : "null after substitution while enhancing " + toString();
         return enhancedMethod;

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/descriptors/JavaPropertyDescriptor.java

@@ -77,6 +77,7 @@ public class JavaPropertyDescriptor extends PropertyDescriptorImpl implements Ja
             newGetter = new PropertyGetterDescriptorImpl(
                     enhanced, getter.getAnnotations(), getter.getModality(), getter.getVisibility(),
                     getter.hasBody(), getter.isDefault(), getter.isExternal(), getKind(), getter, getter.getSource());
+            newGetter.setInitialSignatureDescriptor(getter.getInitialSignatureDescriptor());
             newGetter.initialize(enhancedReturnType);
         }
 
@@ -86,6 +87,7 @@ public class JavaPropertyDescriptor extends PropertyDescriptorImpl implements Ja
             newSetter = new PropertySetterDescriptorImpl(
                     enhanced, setter.getAnnotations(), setter.getModality(), setter.getVisibility(),
                     setter.hasBody(), setter.isDefault(), setter.isExternal(), getKind(), setter, setter.getSource());
+            newSetter.setInitialSignatureDescriptor(newSetter.getInitialSignatureDescriptor());
             newSetter.initialize(setter.getValueParameters().get(0));
         }
 

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaClassMemberScope.kt

@@ -396,12 +396,16 @@ public class LazyJavaClassMemberScope(
                 propertyDescriptor, getterMethod.annotations, /* isDefault = */false,
                 /* isExternal = */ false, getterMethod.source
         ).apply {
+            initialSignatureDescriptor = getterMethod
             initialize(propertyDescriptor.type)
         }
 
         val setter = setterMethod?.let { setterMethod ->
             DescriptorFactory.createSetter(propertyDescriptor, setterMethod.annotations, /* isDefault = */false,
-            /* isExternal = */ false, setterMethod.visibility, setterMethod.source)
+            /* isExternal = */ false, setterMethod.visibility, setterMethod.source
+            ).apply {
+                initialSignatureDescriptor = setterMethod
+            }
         }
 
         return propertyDescriptor.apply { initialize(getter, setter) }

core/descriptors/src/org/jetbrains/kotlin/descriptors/FunctionDescriptor.java

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.descriptors;
 
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.types.TypeSubstitutor;
 
 import java.util.Collection;
@@ -38,6 +39,9 @@ public interface FunctionDescriptor extends CallableMemberDescriptor {
     @NotNull
     Collection<? extends FunctionDescriptor> getOverriddenDescriptors();
 
+    @Nullable
+    FunctionDescriptor getInitialSignatureDescriptor();
+
     @NotNull
     @Override
     FunctionDescriptor copy(DeclarationDescriptor newOwner, Modality modality, Visibility visibility, Kind kind, boolean copyOverrides);

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/FunctionDescriptorImpl.java

@@ -50,6 +50,8 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
     private final Set<FunctionDescriptor> overriddenFunctions = SmartSet.create();
     private final FunctionDescriptor original;
     private final Kind kind;
+    @Nullable
+    private FunctionDescriptor initialSignatureDescriptor = null;
 
     protected FunctionDescriptorImpl(
             @NotNull DeclarationDescriptor containingDeclaration,
@@ -271,7 +273,7 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
         return doSubstitute(originalSubstitutor,
                             newOwner, newModality, newVisibility, isOperator, isInfix, isExternal, isInline, isTailrec, original, copyOverrides, kind,
                             getValueParameters(), getExtensionReceiverParameterType(), getReturnType(),
-                            null, false);
+                            null, /* preserveSource = */ false, /* signatureChange */ false);
     }
 
     @Nullable
@@ -299,7 +301,8 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
             @Nullable KotlinType newExtensionReceiverParameterType,
             @NotNull KotlinType newReturnType,
             @Nullable Name name,
-            boolean preserveSource
+            boolean preserveSource,
+            boolean signatureChange
     ) {
         FunctionDescriptorImpl substitutedDescriptor = createSubstitutedCopy(newOwner, original, kind, name, preserveSource);
 
@@ -362,6 +365,12 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
         substitutedDescriptor.setInline(isInline);
         substitutedDescriptor.setTailrec(isTailrec);
 
+        if (signatureChange || getInitialSignatureDescriptor() != null) {
+            FunctionDescriptor initialSignature = (getInitialSignatureDescriptor() != null ? getInitialSignatureDescriptor() : this);
+            FunctionDescriptor initialSignatureSubstituted = initialSignature.substitute(substitutor);
+            substitutedDescriptor.setInitialSignatureDescriptor(initialSignatureSubstituted);
+        }
+
         if (copyOverrides) {
             for (FunctionDescriptor overriddenFunction : overriddenFunctions) {
                 substitutedDescriptor.addOverriddenDescriptor(overriddenFunction.substitute(substitutor));
@@ -424,4 +433,14 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
         }
         return result;
     }
+
+    @Override
+    @Nullable
+    public FunctionDescriptor getInitialSignatureDescriptor() {
+        return initialSignatureDescriptor;
+    }
+
+    public void setInitialSignatureDescriptor(@Nullable FunctionDescriptor initialSignatureDescriptor) {
+        this.initialSignatureDescriptor = initialSignatureDescriptor;
+    }
 }

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/PropertyAccessorDescriptorImpl.java

@@ -37,6 +37,8 @@ public abstract class PropertyAccessorDescriptorImpl extends DeclarationDescript
     private final PropertyDescriptor correspondingProperty;
     private final Kind kind;
     private Visibility visibility;
+    @Nullable
+    private FunctionDescriptor initialSignatureDescriptor = null;
 
     public PropertyAccessorDescriptorImpl(
             @NotNull Modality modality,
@@ -189,4 +191,14 @@ public abstract class PropertyAccessorDescriptorImpl extends DeclarationDescript
     @NotNull
     @Override
     public abstract PropertyAccessorDescriptor getOriginal();
+
+    @Override
+    @Nullable
+    public FunctionDescriptor getInitialSignatureDescriptor() {
+        return initialSignatureDescriptor;
+    }
+
+    public void setInitialSignatureDescriptor(@Nullable FunctionDescriptor initialSignatureDescriptor) {
+        this.initialSignatureDescriptor = initialSignatureDescriptor;
+    }
 }

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/PropertyDescriptorImpl.java

@@ -257,15 +257,18 @@ public class PropertyDescriptorImpl extends VariableDescriptorWithInitializerImp
 
         PropertyGetterDescriptorImpl newGetter = getter == null ? null : new PropertyGetterDescriptorImpl(
                 substitutedDescriptor, getter.getAnnotations(), newModality, getter.getVisibility(),
-                getter.hasBody(), getter.isDefault(), getter.isExternal(), kind, original == null ? null : original.getGetter(), SourceElement.NO_SOURCE
+                getter.hasBody(), getter.isDefault(), getter.isExternal(), kind, original == null ? null : original.getGetter(),
+                SourceElement.NO_SOURCE
         );
         if (newGetter != null) {
             KotlinType returnType = getter.getReturnType();
+            newGetter.setInitialSignatureDescriptor(getSubstitutedInitialSignatureDescriptor(substitutor, getter));
             newGetter.initialize(returnType != null ? substitutor.substitute(returnType, Variance.OUT_VARIANCE) : null);
         }
         PropertySetterDescriptorImpl newSetter = setter == null ? null : new PropertySetterDescriptorImpl(
                 substitutedDescriptor, setter.getAnnotations(), newModality, setter.getVisibility(),
-                setter.hasBody(), setter.isDefault(), setter.isExternal(), kind, original == null ? null : original.getSetter(), SourceElement.NO_SOURCE
+                setter.hasBody(), setter.isDefault(), setter.isExternal(), kind, original == null ? null : original.getSetter(),
+                SourceElement.NO_SOURCE
         );
         if (newSetter != null) {
             List<ValueParameterDescriptor> substitutedValueParameters = FunctionDescriptorImpl.getSubstitutedValueParameters(
@@ -285,6 +288,7 @@ public class PropertyDescriptorImpl extends VariableDescriptorWithInitializerImp
             if (substitutedValueParameters.size() != 1) {
                 throw new IllegalStateException();
             }
+            newSetter.setInitialSignatureDescriptor(getSubstitutedInitialSignatureDescriptor(substitutor, setter));
             newSetter.initialize(substitutedValueParameters.get(0));
         }
 
@@ -299,6 +303,15 @@ public class PropertyDescriptorImpl extends VariableDescriptorWithInitializerImp
         return substitutedDescriptor;
     }
 
+    private static FunctionDescriptor getSubstitutedInitialSignatureDescriptor(
+            @NotNull TypeSubstitutor substitutor,
+            @NotNull PropertyAccessorDescriptor accessorDescriptor
+    ) {
+        return accessorDescriptor.getInitialSignatureDescriptor() != null
+               ? accessorDescriptor.getInitialSignatureDescriptor().substitute(substitutor)
+               : null;
+    }
+
     @NotNull
     protected PropertyDescriptorImpl createSubstitutedCopy(
             @NotNull DeclarationDescriptor newOwner,

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/SimpleFunctionDescriptorImpl.java

@@ -115,7 +115,7 @@ public class SimpleFunctionDescriptorImpl extends FunctionDescriptorImpl impleme
                 TypeSubstitutor.EMPTY, getContainingDeclaration(), getModality(), getVisibility(),
                 isOperator(), isInfix(), isExternal(), isInline(), isTailrec(),
                 null, /* copyOverrides = */ true, getKind(), getValueParameters(), getExtensionReceiverParameterType(), getReturnType(), name,
-                /* preserveSource = */ true);
+                /* preserveSource = */ true, /* signatureChange = */ true);
     }
 
     @NotNull
@@ -126,6 +126,6 @@ public class SimpleFunctionDescriptorImpl extends FunctionDescriptorImpl impleme
                 TypeSubstitutor.EMPTY, getContainingDeclaration(), getModality(), getVisibility(),
                 isOperator(), isInfix(), isExternal(), isInline(), isTailrec(),
                 null, /* copyOverrides = */ true, getKind(), valueParameters, getExtensionReceiverParameterType(), getReturnType(), null,
-                /* preserveSource = */ true);
+                /* preserveSource = */ true, /* signatureChange = */ true);
     }
 }