FIR: Optimize Java types mapping

- Avoid duplicated computations for arguments
- Do not recreate types if they weren't enhanced

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/JavaUtils.kt

@@ -96,12 +96,11 @@ internal fun JavaClassifierType.toFirResolvedTypeRef(
     forTypeParameterBounds: Boolean
 ): FirResolvedTypeRef {
     val coneType =
-        this.toConeKotlinTypeWithoutEnhancement(session, javaTypeParameterStack, forTypeParameterBounds).run {
-            if (isForSupertypes)
-                this.lowerBoundIfFlexible()
-            else
-                this
-        }
+        if (isForSupertypes)
+            toConeKotlinTypeForFlexibleBound(session, javaTypeParameterStack, isLowerBound = true, forTypeParameterBounds)
+        else
+            toConeKotlinTypeWithoutEnhancement(session, javaTypeParameterStack, forTypeParameterBounds)
+
     return buildResolvedTypeRef {
         type = coneType
         this@toFirResolvedTypeRef.annotations.mapTo(annotations) { it.toFirAnnotationCall(session, javaTypeParameterStack) }
@@ -166,7 +165,10 @@ private fun JavaClassifierType.toConeKotlinTypeWithoutEnhancement(
     forTypeParameterBounds: Boolean = false
 ): ConeKotlinType {
     val lowerBound = toConeKotlinTypeForFlexibleBound(session, javaTypeParameterStack, isLowerBound = true, forTypeParameterBounds)
-    val upperBound = toConeKotlinTypeForFlexibleBound(session, javaTypeParameterStack, isLowerBound = false, forTypeParameterBounds)
+    val upperBound =
+        toConeKotlinTypeForFlexibleBound(
+            session, javaTypeParameterStack, isLowerBound = false, forTypeParameterBounds, lowerBound
+        )
 
     return if (isRaw) ConeRawType(lowerBound, upperBound) else ConeFlexibleType(lowerBound, upperBound)
 }
@@ -263,8 +265,9 @@ private fun JavaClassifierType.toConeKotlinTypeForFlexibleBound(
     session: FirSession,
     javaTypeParameterStack: JavaTypeParameterStack,
     isLowerBound: Boolean,
-    forTypeParameterBounds: Boolean
-): ConeKotlinType {
+    forTypeParameterBounds: Boolean,
+    lowerBound: ConeLookupTagBasedType? = null
+): ConeLookupTagBasedType {
     return when (val classifier = classifier) {
         is JavaClass -> {
             //val classId = classifier.classId!!
@@ -275,6 +278,11 @@ private fun JavaClassifierType.toConeKotlinTypeForFlexibleBound(
             }
 
             val lookupTag = ConeClassLikeLookupTagImpl(classId)
+            if (!isLowerBound && !isRaw && lookupTag == lowerBound?.lookupTag) {
+                return lookupTag.constructClassType(
+                    lowerBound.typeArguments, isNullable = true
+                )
+            }
 
             val mappedTypeArguments = if (isRaw) {
 
@@ -306,7 +314,7 @@ private fun JavaClassifierType.toConeKotlinTypeForFlexibleBound(
             val symbol = javaTypeParameterStack[classifier]
             ConeTypeParameterTypeImpl(symbol.toLookupTag(), isNullable = !isLowerBound)
         }
-        else -> ConeClassErrorType(reason = "Unexpected classifier: $classifier")
+        else -> ConeKotlinErrorType("Unexpected classifier: $classifier")
     }
 }
 

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/enhancement/javaTypeUtils.kt

@@ -91,8 +91,9 @@ private fun ConeKotlinType.enhanceConeKotlinType(
                 session, TypeComponentPosition.FLEXIBLE_UPPER, qualifiers, index
             )
 
-            when (this) {
-                is ConeRawType -> ConeRawType(lowerResult, upperResult)
+            when {
+                lowerResult === lowerBound && upperResult === upperBound -> this
+                this is ConeRawType -> ConeRawType(lowerResult, upperResult)
                 else -> coneFlexibleOrSimpleType(
                     session, lowerResult, upperResult, isNotNullTypeParameter = qualifiers(index).isNotNullTypeParameter
                 )
@@ -165,6 +166,8 @@ private fun ConeKotlinType.enhanceInflexibleType(
     val effectiveQualifiers = qualifiers(index)
     val enhancedTag = originalTag.enhanceMutability(effectiveQualifiers, position)
 
+    var wereChangesInArgs = false
+
     val enhancedArguments = if (this is RawType) {
         // TODO: Support enhancing for raw types
         typeArguments
@@ -178,13 +181,19 @@ private fun ConeKotlinType.enhanceInflexibleType(
                 require(arg is ConeKotlinType) { "Should be invariant type: $arg" }
                 globalArgIndex += arg.subtreeSize()
 
-                arg.enhanceConeKotlinType(session, qualifiers, globalArgIndex)
+                arg.enhanceConeKotlinType(session, qualifiers, globalArgIndex).also {
+                    if (it !== arg) {
+                        wereChangesInArgs = true
+                    }
+                }
             }
         }.toTypedArray()
     }
 
     val enhancedNullability = getEnhancedNullability(effectiveQualifiers, position)
 
+    if (!wereChangesInArgs && originalTag == enhancedTag && enhancedNullability == isNullable) return this
+
     val enhancedType = enhancedTag.constructType(enhancedArguments, enhancedNullability)
 
     // TODO: why all of these is needed