[FIR] Add ConeKotlinTypeConflictingProjection, return it from substituteArgument instead of ConeStarProjection in appropriate cases, remove plus operator from ProjectionKind

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ConeTypeCompatibilityChecker.kt

@@ -312,6 +312,7 @@ internal object ConeTypeCompatibilityChecker {
                     // considered compatible.
                     is ConeKotlinTypeProjectionIn -> BoundTypeArgument(coneTypeProjection.type, Variance.IN_VARIANCE)
                     is ConeKotlinTypeProjectionOut -> BoundTypeArgument(coneTypeProjection.type, Variance.OUT_VARIANCE)
+                    is ConeKotlinTypeConflictingProjection -> BoundTypeArgument(coneTypeProjection.type, Variance.INVARIANT)
                     is ConeKotlinType ->
                         when ((typeParameter as? FirTypeParameter)?.variance) {
                             Variance.IN_VARIANCE -> BoundTypeArgument(coneTypeProjection.type, Variance.IN_VARIANCE)

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt

@@ -15,16 +15,6 @@ import org.jetbrains.kotlin.utils.addToStdlib.foldMap
 
 enum class ProjectionKind {
     STAR, IN, OUT, INVARIANT;
-
-    operator fun plus(other: ProjectionKind): ProjectionKind {
-        return when {
-            this == other -> this
-            this == STAR || other == STAR -> STAR
-            this == INVARIANT -> other
-            other == INVARIANT -> this
-            else -> STAR
-        }
-    }
 }
 
 sealed class ConeTypeProjection : TypeArgumentMarker {
@@ -54,6 +44,11 @@ data class ConeKotlinTypeProjectionOut(override val type: ConeKotlinType) : Cone
         get() = ProjectionKind.OUT
 }
 
+data class ConeKotlinTypeConflictingProjection(override val type: ConeKotlinType) : ConeKotlinTypeProjection() {
+    override val kind: ProjectionKind
+        get() = ProjectionKind.INVARIANT
+}
+
 val ConeTypeProjection.type: ConeKotlinType?
     get() = when (this) {
         ConeStarProjection -> null

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/TypeRenderer.kt

@@ -59,6 +59,7 @@ private fun ConeKotlinType.renderAttributes(): String {
 fun ConeTypeProjection.render(): String {
     return when (this) {
         ConeStarProjection -> "*"
+        is ConeKotlinTypeConflictingProjection -> "CONFLICTING-PROJECTION ${type.render()}"
         is ConeKotlinTypeProjectionIn -> "in ${type.render()}"
         is ConeKotlinTypeProjectionOut -> "out ${type.render()}"
         is ConeKotlinType -> render()

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrTypeConverter.kt

@@ -9,7 +9,6 @@ import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
 import org.jetbrains.kotlin.fir.expressions.classId
 import org.jetbrains.kotlin.fir.languageVersionSettings
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
-import org.jetbrains.kotlin.fir.resolve.inference.inferenceComponents
 import org.jetbrains.kotlin.fir.resolve.substitution.AbstractConeSubstitutor
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.typeContext
@@ -19,6 +18,7 @@ import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.IrTypeArgument
+import org.jetbrains.kotlin.ir.types.IrTypeProjection
 import org.jetbrains.kotlin.ir.types.impl.IrSimpleTypeImpl
 import org.jetbrains.kotlin.ir.types.impl.IrStarProjectionImpl
 import org.jetbrains.kotlin.ir.types.impl.makeTypeProjection
@@ -165,16 +165,16 @@ class Fir2IrTypeConverter(
     }
 
     private fun ConeTypeProjection.toIrTypeArgument(typeContext: ConversionTypeContext): IrTypeArgument {
+        fun toIrTypeArgument(type: ConeKotlinType, variance: Variance): IrTypeProjection {
+            val irType = type.toIrType(typeContext)
+            return makeTypeProjection(irType, if (typeContext.invariantProjection) Variance.INVARIANT else variance)
+        }
+
         return when (this) {
             ConeStarProjection -> IrStarProjectionImpl
-            is ConeKotlinTypeProjectionIn -> {
-                val irType = this.type.toIrType(typeContext)
-                makeTypeProjection(irType, if (typeContext.invariantProjection) Variance.INVARIANT else Variance.IN_VARIANCE)
-            }
-            is ConeKotlinTypeProjectionOut -> {
-                val irType = this.type.toIrType(typeContext)
-                makeTypeProjection(irType, if (typeContext.invariantProjection) Variance.INVARIANT else Variance.OUT_VARIANCE)
-            }
+            is ConeKotlinTypeProjectionIn -> toIrTypeArgument(this.type, Variance.IN_VARIANCE)
+            is ConeKotlinTypeProjectionOut -> toIrTypeArgument(this.type, Variance.OUT_VARIANCE)
+            is ConeKotlinTypeConflictingProjection -> toIrTypeArgument(this.type, Variance.INVARIANT)
             is ConeKotlinType -> {
                 if (this is ConeCapturedType && this in capturedTypeCache && this.isRecursive(mutableSetOf())) {
                     // Recursive captured type, e.g., Recursive<R> where R : Recursive<R>, ...

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/TypeExpansionUtils.kt

@@ -107,12 +107,32 @@ private fun mapTypeAliasArguments(
                 else -> mappedType
             }
 
-            return when (mappedProjection.kind + projection.kind) {
-                ProjectionKind.STAR -> ConeStarProjection
-                ProjectionKind.IN -> ConeKotlinTypeProjectionIn(mappedType)
-                ProjectionKind.OUT -> ConeKotlinTypeProjectionOut(mappedType)
-                ProjectionKind.INVARIANT -> mappedType
+            fun convertProjectionKindToConeTypeProjection(projectionKind: ProjectionKind): ConeTypeProjection {
+                return when (projectionKind) {
+                    ProjectionKind.STAR -> ConeStarProjection
+                    ProjectionKind.IN -> ConeKotlinTypeProjectionIn(mappedType)
+                    ProjectionKind.OUT -> ConeKotlinTypeProjectionOut(mappedType)
+                    ProjectionKind.INVARIANT -> mappedType
+                }
             }
+
+            if (mappedProjection.kind == projection.kind) {
+                return convertProjectionKindToConeTypeProjection(mappedProjection.kind)
+            }
+
+            if (mappedProjection.kind == ProjectionKind.STAR || projection.kind == ProjectionKind.STAR) {
+                return ConeStarProjection
+            }
+
+            if (mappedProjection.kind == ProjectionKind.INVARIANT) {
+                return convertProjectionKindToConeTypeProjection(projection.kind)
+            }
+
+            if (projection.kind == ProjectionKind.INVARIANT) {
+                return convertProjectionKindToConeTypeProjection(mappedProjection.kind)
+            }
+
+            return ConeKotlinTypeConflictingProjection(mappedType)
         }
     }
 

compiler/tests-compiler-utils/tests/org/jetbrains/kotlin/fir/RenderingForDebugInfo.kt

@@ -49,6 +49,7 @@ private fun ConeTypeProjection.renderForDebugInfo(): String {
         ConeStarProjection -> "*"
         is ConeKotlinTypeProjectionIn -> "in ${type.renderForDebugInfo()}"
         is ConeKotlinTypeProjectionOut -> "out ${type.renderForDebugInfo()}"
+        is ConeKotlinTypeConflictingProjection -> "CONFLICTING-PROJECTION ${type.renderForDebugInfo()}"
         is ConeKotlinType -> renderForDebugInfo()
     }
 }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/fir/KtDeclarationAndFirDeclarationEqualityChecker.kt

@@ -162,6 +162,7 @@ object KtDeclarationAndFirDeclarationEqualityChecker {
         ConeStarProjection -> "*"
         is ConeKotlinTypeProjectionIn -> "in ${type.renderTypeAsKotlinType()}"
         is ConeKotlinTypeProjectionOut -> "out ${type.renderTypeAsKotlinType()}"
+        is ConeKotlinTypeConflictingProjection -> "CONFLICTING-PROJECTION ${type.renderTypeAsKotlinType()}"
         is ConeKotlinType -> renderTypeAsKotlinType()
     }