Don't lose upper non-expected type constraints to include them to intersection type during finding the result type of the fixing type variable

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java

@@ -28737,6 +28737,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/typeParameters/dontIntersectUpperBoundWithExpectedType.kt");
             }
 
+            @Test
+            @TestMetadata("dontLoseUpperNonExpectedTypeConstraints.kt")
+            public void testDontLoseUpperNonExpectedTypeConstraints() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/dontLoseUpperNonExpectedTypeConstraints.kt");
+            }
+
             @Test
             @TestMetadata("extFunctionTypeAsUpperBound.kt")
             public void testExtFunctionTypeAsUpperBound() throws Exception {

compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/inference/model/MutableConstraintStorage.kt

@@ -125,6 +125,16 @@ class MutableVariableWithConstraints private constructor(
         if (old.position.from is DeclaredUpperBoundConstraintPosition<*> && new.position.from !is DeclaredUpperBoundConstraintPosition<*>)
             return false
 
+        /*
+         * We discriminate upper expected type constraints during finding a result type to fix variable (see ResultTypeResolver.kt):
+         * namely, we don't intersect the expected type with other upper constraints' types to prevent cases like this:
+         *  fun <T : String> materialize(): T = null as T
+         *  val bar: Int = materialize() // T is inferred into String & Int without discriminating upper expected type constraints
+         * So here we shouldn't lose upper non-expected type constraints.
+         */
+        if (old.position.from is ExpectedTypeConstraintPosition<*> && new.position.from !is ExpectedTypeConstraintPosition<*> && old.kind.isUpper() && new.kind.isUpper())
+            return false
+
         return when (old.kind) {
             ConstraintKind.EQUALITY -> true
             ConstraintKind.LOWER -> new.kind.isLower()

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

@@ -9,9 +9,9 @@ fun <T : Foo> foo(): T? {
 }
 
 fun main() {
-    val a: Bar? = <!DEBUG_INFO_EXPRESSION_TYPE("Bar?")!><!TYPE_MISMATCH!>foo<!>()<!>
+    val a: Bar? = <!DEBUG_INFO_EXPRESSION_TYPE("Foo? & Bar?")!>foo()<!>
 }
 
 
 fun <T : Appendable> wtf(): T = TODO()
-val bar: Int = <!TYPE_MISMATCH!>wtf<!>() // happily compiles
+val bar: Int = wtf() // happily compiles

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

@@ -0,0 +1,15 @@
+// FIR_IDENTICAL
+// !DIAGNOSTICS: -UNUSED_PARAMETER -CAST_NEVER_SUCCEEDS
+
+open class Expression<K>
+
+class ModOp<T : Number?, S : Number?>(
+    val expr1: Expression<T>,
+    val expr2: Expression<S>
+)
+
+class QueryParameter<A> : Expression<A>()
+
+fun <T, S : T?> Expression<in S>.wrap(value: T): QueryParameter<T> = null as QueryParameter<T>
+
+fun <T : Number?, S : T> Expression<T>.rem(t: S): ModOp<T, S> = ModOp(this, wrap(t))

compiler/testData/diagnostics/tests/typeParameters/dontLoseUpperNonExpectedTypeConstraints.txt

@@ -0,0 +1,27 @@
+package
+
+public fun </*0*/ T : kotlin.Number?, /*1*/ S : T> Expression<T>.rem(/*0*/ t: S): ModOp<T, S>
+public fun </*0*/ T, /*1*/ S : T?> Expression<in S>.wrap(/*0*/ value: T): QueryParameter<T>
+
+public open class Expression</*0*/ K> {
+    public constructor Expression</*0*/ K>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class ModOp</*0*/ T : kotlin.Number?, /*1*/ S : kotlin.Number?> {
+    public constructor ModOp</*0*/ T : kotlin.Number?, /*1*/ S : kotlin.Number?>(/*0*/ expr1: Expression<T>, /*1*/ expr2: Expression<S>)
+    public final val expr1: Expression<T>
+    public final val expr2: Expression<S>
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class QueryParameter</*0*/ A> : Expression<A> {
+    public constructor QueryParameter</*0*/ A>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/typeParameters/kt42042.fir.kt

@@ -6,6 +6,6 @@ sealed class Subtype<A1, B1> {
 }
 
 fun <A, B> unsafeCast(value: A): B {
-    val proof: Subtype<A, B> = Subtype.Trivial()
+    val proof: Subtype<A, B> = <!UPPER_BOUND_VIOLATED!>Subtype.Trivial()<!>
     return proof.cast(value)
 }

compiler/testData/diagnostics/tests/typeParameters/kt42396.fir.kt

@@ -11,7 +11,7 @@ fun <F> materializeInvOfAAndB(): Inv<F> where F : A, F : B = Inv()
 fun <F> wrapAAndBToOut(x: F): Out<F> where F : A, F : B = Out()
 
 fun main(a: A) {
-    val x: Out<A> = <!TYPE_MISMATCH!>materializeOutOfAAndB<!>() // OI: inferred type A is not a subtype of B; `F` is instantiated as `A`, so upper bounds was violated
-    val y: Inv<A> = <!TYPE_MISMATCH!>materializeInvOfAAndB()<!> // OI and NI: required B, found A
-    val z: Out<A> = wrapAAndBToOut(<!TYPE_MISMATCH!>a<!>) // OI and NI: required B, found A
+    val x: Out<A> = materializeOutOfAAndB() // OI: inferred type A is not a subtype of B; `F` is instantiated as `A`, so upper bounds was violated
+    val y: Inv<A> = materializeInvOfAAndB() // OI and NI: required B, found A
+    val z: Out<A> = <!INAPPLICABLE_CANDIDATE!>wrapAAndBToOut<!>(a) // OI and NI: required B, found A
 }

compiler/testData/diagnostics/tests/typeParameters/kt42472.fir.kt

@@ -7,6 +7,6 @@ fun interface ReadOnlyProperty<in T, out V> {
 }
 
 class Problem {
-    val variable: Int by <!DELEGATE_SPECIAL_FUNCTION_NONE_APPLICABLE!><!TYPE_MISMATCH!>delegate<!>()<!> // delegate returns `ReadOnlyProperty<Problem, {CharSequence & Int}>`
-    fun <T : CharSequence> delegate() = null <!CAST_NEVER_SUCCEEDS!>as<!> ReadOnlyProperty<Problem, T>
+    val variable: Int by delegate() // delegate returns `ReadOnlyProperty<Problem, {CharSequence & Int}>`
+    fun <T : CharSequence> delegate() = null as ReadOnlyProperty<Problem, T>
 }

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -28833,6 +28833,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/typeParameters/dontIntersectUpperBoundWithExpectedType.kt");
             }
 
+            @Test
+            @TestMetadata("dontLoseUpperNonExpectedTypeConstraints.kt")
+            public void testDontLoseUpperNonExpectedTypeConstraints() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/typeParameters/dontLoseUpperNonExpectedTypeConstraints.kt");
+            }
+
             @Test
             @TestMetadata("extFunctionTypeAsUpperBound.kt")
             public void testExtFunctionTypeAsUpperBound() throws Exception {