FIR: store in ARGUMENT_TYPE_MISMATCH whether it's due to nullability

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

@@ -288,6 +288,7 @@ object DIAGNOSTICS_LIST : DiagnosticList() {
         val ARGUMENT_TYPE_MISMATCH by error<PsiElement> {
             parameter<ConeKotlinType>("expectedType")
             parameter<ConeKotlinType>("actualType")
+            parameter<Boolean>("isMismatchDueToNullability")
         }
 
         val NULL_FOR_NONNULL_TYPE by error<PsiElement> { }

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

@@ -235,7 +235,7 @@ object FirErrors {
     val TYPE_MISMATCH by error2<PsiElement, ConeKotlinType, ConeKotlinType>()
     val THROWABLE_TYPE_MISMATCH by error1<PsiElement, ConeKotlinType>()
     val CONDITION_TYPE_MISMATCH by error1<PsiElement, ConeKotlinType>()
-    val ARGUMENT_TYPE_MISMATCH by error2<PsiElement, ConeKotlinType, ConeKotlinType>()
+    val ARGUMENT_TYPE_MISMATCH by error3<PsiElement, ConeKotlinType, ConeKotlinType, Boolean>()
     val NULL_FOR_NONNULL_TYPE by error0<PsiElement>()
     val INAPPLICABLE_LATEINIT_MODIFIER by error1<KtModifierListOwner, String>(SourceElementPositioningStrategies.LATEINIT_MODIFIER)
     val VARARG_OUTSIDE_PARENTHESES by error0<KtExpression>()

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

@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.DECL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.FIR
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.FQ_NAMES_IN_TYPES
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.NAME
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.NOT_RENDERED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.NULLABLE_STRING
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.RENDER_CLASS_OR_OBJECT
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.RENDER_TYPE
@@ -563,7 +564,7 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
             map.put(TYPE_MISMATCH, "Type mismatch: inferred type is {1} but {0} was expected", TO_STRING, TO_STRING)
             map.put(THROWABLE_TYPE_MISMATCH, "Throwable type mismatch: actual type is {0}", TO_STRING)
             map.put(CONDITION_TYPE_MISMATCH, "Condition type mismatch: inferred type is {0} but Boolean was expected", TO_STRING)
-            map.put(ARGUMENT_TYPE_MISMATCH, "Argument type mismatch: actual type is {1} but {0} was expected", RENDER_TYPE, RENDER_TYPE)
+            map.put(ARGUMENT_TYPE_MISMATCH, "Argument type mismatch: actual type is {1} but {0} was expected", RENDER_TYPE, RENDER_TYPE, NOT_RENDERED)
             map.put(ASSIGNMENT_TYPE_MISMATCH, "Assignment type mismatch: actual type is {1} but {0} was expected", RENDER_TYPE, RENDER_TYPE)
             map.put(
                 RESULT_TYPE_MISMATCH,

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

@@ -136,7 +136,8 @@ private fun mapInapplicableCandidateError(
             is ArgumentTypeMismatch -> FirErrors.ARGUMENT_TYPE_MISMATCH.on(
                 rootCause.argument.source ?: source,
                 rootCause.expectedType,
-                rootCause.actualType
+                rootCause.actualType,
+                rootCause.isMismatchDueToNullability
             )
             is NullForNotNullType -> FirErrors.NULL_FOR_NONNULL_TYPE.on(
                 rootCause.argument.source ?: source

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt

@@ -375,10 +375,18 @@ private fun checkApplicabilityForArgumentType(
             return type
         }
 
+        // Reaching here means argument types mismatch, and we want to record whether it's due to the nullability by checking a subtype
+        // relation with nullable expected type.
+        val isMismatchDueToNullability = AbstractTypeChecker.isSubtypeOf(
+            context.session.typeContext,
+            argumentType,
+            actualExpectedType.withNullability(ConeNullability.NULLABLE, context.session.typeContext)
+        )
         return ArgumentTypeMismatch(
             tryGetConeTypeThatCompatibleWithKtType(actualExpectedType),
             tryGetConeTypeThatCompatibleWithKtType(argumentType),
-            argument
+            argument,
+            isMismatchDueToNullability
         )
     }
 

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/ResolutionDiagnostic.kt

@@ -93,7 +93,8 @@ sealed class UnstableSmartCast(
 class ArgumentTypeMismatch(
     val expectedType: ConeKotlinType,
     val actualType: ConeKotlinType,
-    val argument: FirExpression
+    val argument: FirExpression,
+    val isMismatchDueToNullability: Boolean,
 ) : ResolutionDiagnostic(INAPPLICABLE)
 
 class NullForNotNullType(

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -961,6 +961,7 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
         ArgumentTypeMismatchImpl(
             firSymbolBuilder.typeBuilder.buildKtType(firDiagnostic.a),
             firSymbolBuilder.typeBuilder.buildKtType(firDiagnostic.b),
+            firDiagnostic.c,
             firDiagnostic as FirPsiDiagnostic<*>,
             token,
         )

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -688,6 +688,7 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = ArgumentTypeMismatch::class
         abstract val expectedType: KtType
         abstract val actualType: KtType
+        abstract val isMismatchDueToNullability: Boolean
     }
 
     abstract class NullForNonnullType : KtFirDiagnostic<PsiElement>() {

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -1105,6 +1105,7 @@ internal class ConditionTypeMismatchImpl(
 internal class ArgumentTypeMismatchImpl(
     override val expectedType: KtType,
     override val actualType: KtType,
+    override val isMismatchDueToNullability: Boolean,
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,
 ) : KtFirDiagnostic.ArgumentTypeMismatch(), KtAbstractFirDiagnostic<PsiElement> {