Minor: use more clear and specific naming for LazyClassContext.typeChecker (relevant for MPP with type refinement)

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/LazyClassContext.kt

@@ -45,8 +45,24 @@ interface LazyClassContext {
     val syntheticResolveExtension: SyntheticResolveExtension
     val delegationFilter: DelegationFilter
     val wrappedTypeFactory: WrappedTypeFactory
-    val kotlinTypeChecker: NewKotlinTypeChecker
     val samConversionResolver: SamConversionResolver
     val additionalClassPartsProvider: AdditionalClassPartsProvider
     val sealedClassInheritorsProvider: SealedClassInheritorsProvider
+
+    /**
+     * Important notice!
+     *
+     * This is the type checker of *owner* module, i.e. the module which has declared the class.
+     *
+     * In MPP, we have different "views" on the one and the same class. I.e. if we have a common 'class Foo : Expect',
+     * and on JVM we have 'actual typealias Expect = CharSequence', then from "common view" Foo isn't assigneable to CharSequence,
+     * while from the "JVM view" it is.
+     *
+     * LazyClassContext is usually shared across all such views, so be careful - using this typechecker in "platform views" is not correct.
+     * Relevant entities usually have a separate instance of KotlinTypeChecker/KotlinTypeRefiner, see for example
+     * [org.jetbrains.kotlin.resolve.lazy.descriptors.LazyClassMemberScope].
+     *
+     * See also KT-44898 for example of issues which might happen if the wrong typechecker is used in "platform view".
+     */
+    val kotlinTypeCheckerOfOwnerModule: NewKotlinTypeChecker
 }

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/ResolveSession.java

@@ -504,7 +504,7 @@ public class ResolveSession implements KotlinCodeAnalyzer, LazyClassContext {
 
     @NotNull
     @Override
-    public NewKotlinTypeChecker getKotlinTypeChecker() {
+    public NewKotlinTypeChecker getKotlinTypeCheckerOfOwnerModule() {
         return kotlinTypeChecker;
     }
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassDescriptor.java

@@ -327,16 +327,15 @@ public class LazyClassDescriptor extends ClassDescriptorBase implements ClassDes
         return ScopesHolderForClass.Companion.create(
                 this,
                 c.getStorageManager(),
-                c.getKotlinTypeChecker().getKotlinTypeRefiner(),
+                c.getKotlinTypeCheckerOfOwnerModule().getKotlinTypeRefiner(),
-                kotlinTypeRefiner -> {
+                kotlinTypeRefinerForDependentModule -> {
                     LazyClassMemberScope scopeForDeclaredMembers =
-                            !kotlinTypeRefiner.isRefinementNeededForModule(c.getModuleDescriptor())
+                            !kotlinTypeRefinerForDependentModule.isRefinementNeededForModule(c.getModuleDescriptor())
                                 ? null
-                            // TODO: or kotlinTypeRefiner.getModuleDescriptor()
+                                : scopesHolderForClass.getScope(c.getKotlinTypeCheckerOfOwnerModule().getKotlinTypeRefiner()); // essentially, a scope for owner-module
-                                : scopesHolderForClass.getScope(c.getKotlinTypeChecker().getKotlinTypeRefiner());
 
                     return new LazyClassMemberScope(
-                            c, declarationProvider, this, c.getTrace(), kotlinTypeRefiner,
+                            c, declarationProvider, this, c.getTrace(), kotlinTypeRefinerForDependentModule,
                             scopeForDeclaredMembers
                     );
                 }

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassMemberScope.kt

@@ -53,7 +53,7 @@ open class LazyClassMemberScope(
     declarationProvider: ClassMemberDeclarationProvider,
     thisClass: ClassDescriptorWithResolutionScopes,
     trace: BindingTrace,
-    private val kotlinTypeRefiner: KotlinTypeRefiner = c.kotlinTypeChecker.kotlinTypeRefiner,
+    private val kotlinTypeRefiner: KotlinTypeRefiner = c.kotlinTypeCheckerOfOwnerModule.kotlinTypeRefiner,
     scopeForDeclaredMembers: LazyClassMemberScope? = null
 ) : AbstractLazyMemberScope<ClassDescriptorWithResolutionScopes, ClassMemberDeclarationProvider>(
     c, declarationProvider, thisClass, trace, scopeForDeclaredMembers

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/LocalClassifierAnalyzer.kt

@@ -184,7 +184,7 @@ class LocalClassDescriptorHolder(
                     override val syntheticResolveExtension = this@LocalClassDescriptorHolder.syntheticResolveExtension
                     override val delegationFilter: DelegationFilter = this@LocalClassDescriptorHolder.delegationFilter
                     override val wrappedTypeFactory: WrappedTypeFactory = this@LocalClassDescriptorHolder.wrappedTypeFactory
-                    override val kotlinTypeChecker: NewKotlinTypeChecker = this@LocalClassDescriptorHolder.kotlinTypeChecker
+                    override val kotlinTypeCheckerOfOwnerModule: NewKotlinTypeChecker = this@LocalClassDescriptorHolder.kotlinTypeChecker
                     override val samConversionResolver: SamConversionResolver = this@LocalClassDescriptorHolder.samConversionResolver
                     override val additionalClassPartsProvider: AdditionalClassPartsProvider =
                         this@LocalClassDescriptorHolder.additionalClassPartsProvider

plugins/scripting/scripting-compiler-impl/src/org/jetbrains/kotlin/scripting/resolve/LazyScriptDescriptor.kt

@@ -148,11 +148,11 @@ class LazyScriptDescriptor(
     override fun <R, D> accept(visitor: DeclarationDescriptorVisitor<R, D>, data: D): R =
         visitor.visitScriptDescriptor(this, data)
 
-    override fun createMemberScope(
+    override fun createScopesHolderForClass(
         c: LazyClassContext,
         declarationProvider: ClassMemberDeclarationProvider
     ): ScopesHolderForClass<LazyClassMemberScope> =
-        ScopesHolderForClass.create(this, c.storageManager, c.kotlinTypeChecker.kotlinTypeRefiner) {
+        ScopesHolderForClass.create(this, c.storageManager, c.kotlinTypeCheckerOfOwnerModule.kotlinTypeRefiner) {
             LazyScriptClassMemberScope(
                 // Must be a ResolveSession for scripts
                 c as ResolveSession,