[AA] Provide API for obtaining array element type of KtType

KTIJ-23199

analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/components/KtFe10TypeProvider.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.analysis.api.lifetime.KtLifetimeToken
 import org.jetbrains.kotlin.analysis.api.types.KtType
 import org.jetbrains.kotlin.analysis.api.types.KtTypeNullability
 import org.jetbrains.kotlin.analysis.api.lifetime.withValidityAssertion
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.name.StandardClassIds
@@ -47,8 +48,12 @@ import org.jetbrains.kotlin.types.checker.intersectWrappedTypes
 import org.jetbrains.kotlin.types.error.ErrorType
 import org.jetbrains.kotlin.types.error.ErrorTypeKind
 import org.jetbrains.kotlin.types.error.ErrorUtils
+import org.jetbrains.kotlin.types.typeUtil.builtIns
+import org.jetbrains.kotlin.types.typeUtil.isGenericArrayOfTypeParameter
 import org.jetbrains.kotlin.types.typeUtil.isNothing
+import org.jetbrains.kotlin.types.typeUtil.makeNullable
 import org.jetbrains.kotlin.util.containingNonLocalDeclaration
+import org.jetbrains.kotlin.utils.addToStdlib.applyIf
 
 internal class KtFe10TypeProvider(
     override val analysisSession: KtFe10AnalysisSession
@@ -146,6 +151,16 @@ internal class KtFe10TypeProvider(
         return descriptor.dispatchReceiverParameter?.type?.toKtType(analysisContext)
     }
 
+    override fun getArrayElementType(type: KtType): KtType? {
+        require(type is KtFe10Type)
+        val fe10Type = type.fe10Type
+
+        if (!KotlinBuiltIns.isArrayOrPrimitiveArray(fe10Type)) return null
+
+        val arrayElementType = fe10Type.builtIns.getArrayElementType(fe10Type)
+        return arrayElementType.toKtType(analysisContext)
+    }
+
     private fun areTypesCompatible(a: KotlinType, b: KotlinType): Boolean {
         if (a.isNothing() || b.isNothing() || TypeUtils.equalTypes(a, b) || (a.isNullable() && b.isNullable())) {
             return true

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/components/KtFirTypeProvider.kt

@@ -266,5 +266,10 @@ internal class KtFirTypeProvider(
         }
         return firSymbol.dispatchReceiverType(analysisSession.firSymbolBuilder)
     }
+
+    override fun getArrayElementType(type: KtType): KtType? {
+        require(type is KtFirType)
+        return type.coneType.arrayElementType()?.asKtType()
+    }
 }
 

analysis/analysis-api/src/org/jetbrains/kotlin/analysis/api/components/KtTypeProvider.kt

@@ -42,6 +42,8 @@ public abstract class KtTypeProvider : KtAnalysisSessionComponent() {
     public abstract fun getAllSuperTypes(type: KtType, shouldApproximate: Boolean): List<KtType>
 
     public abstract fun getDispatchReceiverType(symbol: KtCallableSymbol): KtType?
+
+    public abstract fun getArrayElementType(type: KtType): KtType?
 }
 
 public interface KtTypeProviderMixIn : KtAnalysisSessionMixIn {
@@ -152,6 +154,12 @@ public interface KtTypeProviderMixIn : KtAnalysisSessionMixIn {
     @Deprecated("Avoid using this function")
     public fun KtCallableSymbol.getDispatchReceiverType(): KtType? =
         withValidityAssertion { analysisSession.typeProvider.getDispatchReceiverType(this) }
+
+    /**
+     * If provided [KtType] is a primitive type array or [Array], returns the type of the array's elements. Otherwise, returns null.
+     */
+    public fun KtType.getArrayElementType(): KtType? =
+        withValidityAssertion { analysisSession.typeProvider.getArrayElementType(this) }
 }
 
 @Suppress("PropertyName")