[FIR] Add MISPLACED_TYPE_PARAMETER_CONSTRAINTS check

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

@@ -334,6 +334,8 @@ object DIAGNOSTICS_LIST : DiagnosticList() {
         val CYCLIC_GENERIC_UPPER_BOUND by error<FirSourceElement, PsiElement>()
 
         val DEPRECATED_TYPE_PARAMETER_SYNTAX by error<FirSourceElement, KtTypeParameterList>()
+
+        val MISPLACED_TYPE_PARAMETER_CONSTRAINTS by warning<FirSourceElement, KtTypeParameter>()
     }
 
     val REFLECTION by object : DiagnosticGroup("Reflection") {

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

@@ -242,6 +242,7 @@ object FirErrors {
     val RETURN_TYPE_MISMATCH by error2<FirSourceElement, KtExpression, ConeKotlinType, ConeKotlinType>(SourceElementPositioningStrategies.WHOLE_ELEMENT)
     val CYCLIC_GENERIC_UPPER_BOUND by error0<FirSourceElement, PsiElement>()
     val DEPRECATED_TYPE_PARAMETER_SYNTAX by error0<FirSourceElement, KtTypeParameterList>()
+    val MISPLACED_TYPE_PARAMETER_CONSTRAINTS by warning0<FirSourceElement, KtTypeParameter>()
 
     // Reflection
     val EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED by error1<FirSourceElement, KtExpression, FirCallableDeclaration<*>>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)

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

@@ -42,6 +42,7 @@ object FirTypeParameterBoundsChecker : FirTypeParameterChecker() {
         checkBoundUniqueness(declaration, context, reporter)
         checkConflictingBounds(declaration, context, reporter)
         checkTypeAliasBound(declaration, containingDeclaration, context, reporter)
+        checkBoundsPlacement(declaration, context, reporter)
     }
 
     private fun checkFinalUpperBounds(
@@ -147,6 +148,15 @@ object FirTypeParameterBoundsChecker : FirTypeParameterChecker() {
         }
     }
 
+    private fun checkBoundsPlacement(declaration: FirTypeParameter, context: CheckerContext, reporter: DiagnosticReporter) {
+        if (declaration.bounds.size < 2) return
+
+        val (constraint, params) = declaration.bounds.partition { it.isInTypeConstraint() }
+        if (params.isNotEmpty() && constraint.isNotEmpty()) {
+            reporter.reportOn(declaration.source, FirErrors.MISPLACED_TYPE_PARAMETER_CONSTRAINTS, context)
+        }
+    }
+
     private fun KotlinTypeMarker.isRelated(context: TypeCheckerProviderContext, type: KotlinTypeMarker?): Boolean =
         isSubtypeOf(context, type) || isSupertypeOf(context, type)
 

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

@@ -140,6 +140,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MANY_COMPANION_OB
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MANY_IMPL_MEMBER_NOT_IMPLEMENTED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.METHOD_OF_ANY_IMPLEMENTED_IN_INTERFACE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MISPLACED_TYPE_PARAMETER_CONSTRAINTS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MISSING_VAL_ON_ANNOTATION_PARAMETER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MULTIPLE_VARARG_PARAMETERS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MUST_BE_INITIALIZED
@@ -515,6 +516,11 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
 
             map.put(DEPRECATED_TYPE_PARAMETER_SYNTAX, "Type parameters must be placed before the name of the function")
 
+            map.put(
+                MISPLACED_TYPE_PARAMETER_CONSTRAINTS,
+                "If a type parameter has multiple constraints, they all need to be placed in the 'where' clause"
+            )
+
             // Reflection
             map.put(
                 EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED,

compiler/testData/diagnostics/tests/generics/TypeParameterBounds.fir.kt

@@ -1,23 +0,0 @@
-// See KT-9438: Enforce the Single Instantiation Inheritance Rule for type parameters
-
-interface A
-
-interface B
-
-interface D<T>
-
-interface IncorrectF<T : D<A>> where T : <!REPEATED_BOUND!>D<B><!>
-
-interface CorrectF<T> where T : D<A>, T : <!REPEATED_BOUND!>D<B><!>
-
-interface G<T>
-
-interface IncorrectH<T : G<D<A>>> where T : <!REPEATED_BOUND!>G<D<T>><!>
-
-interface CorrectH<T> where T : G<D<A>>, T : <!REPEATED_BOUND!>G<D<B>><!>
-
-interface incorrectJ<T: G<D<T>>> where T : <!REPEATED_BOUND!>G<D<T?>><!>
-
-interface correctJ<T> where T : G<D<T>>, T : <!REPEATED_BOUND!>G<D<T?>><!>
-
-fun <T> bar() where T : D<A>, T : <!REPEATED_BOUND!>D<B><!> {}

compiler/testData/diagnostics/tests/generics/TypeParameterBounds.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // See KT-9438: Enforce the Single Instantiation Inheritance Rule for type parameters
 
 interface A

compiler/testData/diagnostics/tests/generics/invalidArgumentsNumberInWhere.fir.kt

@@ -1,19 +1,19 @@
 class A
 interface I0<T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>>
 interface I1<T> where T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>
-interface I2<T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>> where T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>
+interface I2<<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!><!>> where T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>
 
 fun <E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>> foo0() {}
 fun <E> foo1() where E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!> {}
-fun <E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>> foo2() where E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!> {}
+fun <<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!><!>> foo2() where E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!> {}
 
 val <E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>> E.p1: Int
         get() = 1
 val <E> E.p2: Int where E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>
         get() = 1
-val <E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>> E.p3: Int where E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>
+val <<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!><!>> E.p3: Int where E : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>A<Int><!>
         get() = 1
 
 // See KT-8200
 interface X
-public class EnumAttribute<T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>X<T><!>>(val klass: Class<T>) where T : Enum<T>
+public class EnumAttribute<<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>T : <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>X<T><!><!>>(val klass: Class<T>) where T : Enum<T>

compiler/testData/diagnostics/tests/generics/unresolvedClassifierInWhere.fir.kt

@@ -1,14 +1,14 @@
 interface I0<T : <!UNRESOLVED_REFERENCE!>Unresolved0<String><!>>
 interface I1<T> where T : <!UNRESOLVED_REFERENCE!>Unresolved1<String><!>
-interface I2<T : <!UNRESOLVED_REFERENCE!>Unresolved2<String><!>> where T : <!UNRESOLVED_REFERENCE!>Unresolved3<String><!>
+interface I2<<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>T : <!UNRESOLVED_REFERENCE!>Unresolved2<String><!><!>> where T : <!UNRESOLVED_REFERENCE!>Unresolved3<String><!>
 
 fun <E : <!UNRESOLVED_REFERENCE!>Unresolved4<String><!>> foo0() {}
 fun <E> foo1() where E : <!UNRESOLVED_REFERENCE!>Unresolved5<String><!> {}
-fun <E : <!UNRESOLVED_REFERENCE!>Unresolved6<String><!>> foo2() where E : <!UNRESOLVED_REFERENCE!>Unresolved7<String><!> {}
+fun <<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>E : <!UNRESOLVED_REFERENCE!>Unresolved6<String><!><!>> foo2() where E : <!UNRESOLVED_REFERENCE!>Unresolved7<String><!> {}
 
 val <E : <!UNRESOLVED_REFERENCE!>Unresolved7<!>> E.p1: Int
         get() = 1
 val <E> E.p2: Int where E : <!UNRESOLVED_REFERENCE!>Unresolved8<!>
         get() = 1
-val <E : <!UNRESOLVED_REFERENCE!>Unresolved9<!>> E.p3: Int where E : <!UNRESOLVED_REFERENCE!>Unresolved10<!>
+val <<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>E : <!UNRESOLVED_REFERENCE!>Unresolved9<!><!>> E.p3: Int where E : <!UNRESOLVED_REFERENCE!>Unresolved10<!>
         get() = 1

compiler/testData/diagnostics/tests/typeParameters/misplacedConstraints.fir.kt

@@ -1,13 +0,0 @@
-class Foo<T : Cloneable> where T : Comparable<T> {
-    fun <U : Cloneable> foo(u: U): U where U: Comparable<U> {
-        fun <<!BOUNDS_NOT_ALLOWED_IF_BOUNDED_BY_TYPE_PARAMETER!>T: Any<!>> bar() where T: U {}
-        return u
-    }
-
-    val <U : Cloneable> U.foo: U? where U: Comparable<U>
-       get() { return null }
-}
-
-class Bar<T : Cloneable, U> where U: Comparable<T> {
-
-}

compiler/testData/diagnostics/tests/typeParameters/misplacedConstraints.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class Foo<<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>T : Cloneable<!>> where T : Comparable<T> {
     fun <<!MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>U : Cloneable<!>> foo(u: U): U where U: Comparable<U> {
         fun <<!BOUNDS_NOT_ALLOWED_IF_BOUNDED_BY_TYPE_PARAMETER, MISPLACED_TYPE_PARAMETER_CONSTRAINTS!>T: Any<!>> bar() where T: U {}

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

@@ -1030,6 +1030,12 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.MISPLACED_TYPE_PARAMETER_CONSTRAINTS) { firDiagnostic ->
+        MisplacedTypeParameterConstraintsImpl(
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirErrors.EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED) { firDiagnostic ->
         ExtensionInClassReferenceNotAllowedImpl(
             firSymbolBuilder.callableBuilder.buildCallableSymbol(firDiagnostic.a as FirCallableDeclaration),

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

@@ -731,6 +731,10 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = DeprecatedTypeParameterSyntax::class
     }
 
+    abstract class MisplacedTypeParameterConstraints : KtFirDiagnostic<KtTypeParameter>() {
+        override val diagnosticClass get() = MisplacedTypeParameterConstraints::class
+    }
+
     abstract class ExtensionInClassReferenceNotAllowed : KtFirDiagnostic<KtExpression>() {
         override val diagnosticClass get() = ExtensionInClassReferenceNotAllowed::class
         abstract val referencedDeclaration: KtCallableSymbol

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

@@ -1182,6 +1182,13 @@ internal class DeprecatedTypeParameterSyntaxImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class MisplacedTypeParameterConstraintsImpl(
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.MisplacedTypeParameterConstraints(), KtAbstractFirDiagnostic<KtTypeParameter> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class ExtensionInClassReferenceNotAllowedImpl(
     override val referencedDeclaration: KtCallableSymbol,
     firDiagnostic: FirPsiDiagnostic<*>,