[FIR] Implement TYPEALIAS_SHOULD_EXPAND_TO_CLASS

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -921,6 +921,9 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
     val TYPE_ALIAS by object : DiagnosticGroup("Type alias") {
         val TOPLEVEL_TYPEALIASES_ONLY by error<KtTypeAlias>()
         val RECURSIVE_TYPEALIAS_EXPANSION by error<KtElement>()
+        val TYPEALIAS_SHOULD_EXPAND_TO_CLASS by error<KtElement> {
+            parameter<ConeKotlinType>("expandedType")
+        }
     }
 
     val EXTENDED_CHECKERS by object : DiagnosticGroup("Extended checkers") {

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -500,6 +500,7 @@ object FirErrors {
     // Type alias
     val TOPLEVEL_TYPEALIASES_ONLY by error0<KtTypeAlias>()
     val RECURSIVE_TYPEALIAS_EXPANSION by error0<KtElement>()
+    val TYPEALIAS_SHOULD_EXPAND_TO_CLASS by error1<KtElement, ConeKotlinType>()
 
     // Extended checkers
     val REDUNDANT_VISIBILITY_MODIFIER by warning0<KtModifierListOwner>(SourceElementPositioningStrategies.VISIBILITY_MODIFIER)

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirTypeAliasChecker.kt

@@ -12,12 +12,49 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.declarations.FirMemberDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirTypeAlias
+import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeUnsupportedDynamicType
+import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
+import org.jetbrains.kotlin.fir.resolve.toSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeAliasSymbol
+import org.jetbrains.kotlin.fir.types.*
 
 object FirTypeAliasChecker : FirMemberDeclarationChecker() {
     override fun check(declaration: FirMemberDeclaration, context: CheckerContext, reporter: DiagnosticReporter) {
         if (declaration !is FirTypeAlias) return
+
         if (context.containingDeclarations.lastOrNull() !is FirFile) {
             reporter.reportOn(declaration.source, FirErrors.TOPLEVEL_TYPEALIASES_ONLY, context)
         }
+
+        fun containsTypeParameter(type: ConeKotlinType): Boolean {
+            if (type is ConeTypeParameterType) {
+                return true
+            }
+
+            if (type is ConeClassLikeType && type.lookupTag.toSymbol(context.session) is FirTypeAliasSymbol) {
+                for (typeArgument in type.typeArguments) {
+                    val typeArgumentType = (typeArgument as? ConeKotlinType) ?: (typeArgument as? ConeKotlinTypeProjection)?.type
+                    if (typeArgumentType != null && containsTypeParameter(typeArgumentType)) {
+                        return true
+                    }
+                }
+            }
+
+            return false
+        }
+
+        val expandedTypeRef = declaration.expandedTypeRef
+        val fullyExpandedType = expandedTypeRef.coneType.fullyExpandedType(context.session)
+
+        if (containsTypeParameter(fullyExpandedType) ||
+            fullyExpandedType is ConeClassErrorType && fullyExpandedType.diagnostic is ConeUnsupportedDynamicType
+        ) {
+            reporter.reportOn(
+                declaration.expandedTypeRef.source,
+                FirErrors.TYPEALIAS_SHOULD_EXPAND_TO_CLASS,
+                expandedTypeRef.coneType,
+                context
+            )
+        }
     }
 }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt

@@ -308,6 +308,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SYNTAX
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.THROWABLE_TYPE_MISMATCH
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TOO_MANY_ARGUMENTS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TOPLEVEL_TYPEALIASES_ONLY
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPEALIAS_SHOULD_EXPAND_TO_CLASS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_ARGUMENTS_NOT_ALLOWED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_CANT_BE_USED_FOR_CONST_VAL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_MISMATCH
@@ -1183,6 +1184,11 @@ class FirDefaultErrorMessages {
             // Type alias
             map.put(TOPLEVEL_TYPEALIASES_ONLY, "Nested and local type aliases are not supported")
             map.put(RECURSIVE_TYPEALIAS_EXPANSION, "Recursive type alias in expansion")
+            map.put(
+                TYPEALIAS_SHOULD_EXPAND_TO_CLASS,
+                "Type alias expands to {0}, which is not a class, an interface, or an object",
+                RENDER_TYPE
+            )
 
             // Returns
             map.put(RETURN_NOT_ALLOWED, "'return' is not allowed here")