FIR: Correctly handle nullable/flexible captured types

compiler/fir/analysis-tests/testData/resolve/flexibleCapturedType.kt

@@ -0,0 +1,10 @@
+// FILE: main.kt
+
+fun foo(p: Processor<in CharSequence>, s: String?) {
+    p.process(s)
+}
+
+// FILE: Processor.java
+public interface Processor<T> {
+    boolean process(T t);
+}

compiler/fir/analysis-tests/testData/resolve/flexibleCapturedType.txt

@@ -0,0 +1,4 @@
+FILE: main.kt
+    public final fun foo(p: R|Processor<in kotlin/CharSequence>|, s: R|kotlin/String?|): R|kotlin/Unit| {
+        R|<local>/p|.R|SubstitutionOverride</Processor.process: R|kotlin/Boolean|>|(R|<local>/s|)
+    }

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirDiagnosticsTestGenerated.java

@@ -183,6 +183,11 @@ public class FirDiagnosticsTestGenerated extends AbstractFirDiagnosticsTest {
         runTest("compiler/fir/analysis-tests/testData/resolve/fib.kt");
     }
 
+    @TestMetadata("flexibleCapturedType.kt")
+    public void testFlexibleCapturedType() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/resolve/flexibleCapturedType.kt");
+    }
+
     @TestMetadata("ft.kt")
     public void testFt() throws Exception {
         runTest("compiler/fir/analysis-tests/testData/resolve/ft.kt");

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithLightTreeTestGenerated.java

@@ -183,6 +183,11 @@ public class FirDiagnosticsWithLightTreeTestGenerated extends AbstractFirDiagnos
         runTest("compiler/fir/analysis-tests/testData/resolve/fib.kt");
     }
 
+    @TestMetadata("flexibleCapturedType.kt")
+    public void testFlexibleCapturedType() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/resolve/flexibleCapturedType.kt");
+    }
+
     @TestMetadata("ft.kt")
     public void testFt() throws Exception {
         runTest("compiler/fir/analysis-tests/testData/resolve/ft.kt");

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/LazyBodyIsNotTouchedTilContractsPhaseTestGenerated.java

@@ -183,6 +183,11 @@ public class LazyBodyIsNotTouchedTilContractsPhaseTestGenerated extends Abstract
         runTest("compiler/fir/analysis-tests/testData/resolve/fib.kt");
     }
 
+    @TestMetadata("flexibleCapturedType.kt")
+    public void testFlexibleCapturedType() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/resolve/flexibleCapturedType.kt");
+    }
+
     @TestMetadata("ft.kt")
     public void testFt() throws Exception {
         runTest("compiler/fir/analysis-tests/testData/resolve/ft.kt");

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/ConeTypeContext.kt

@@ -168,7 +168,8 @@ interface ConeTypeContext : TypeSystemContext, TypeSystemOptimizationContext, Ty
 
     override fun CapturedTypeMarker.lowerType(): KotlinTypeMarker? {
         require(this is ConeCapturedType)
-        return this.lowerType
+        if (!this.isMarkedNullable) return this.lowerType
+        return this.lowerType?.makeNullable()
     }
 
     override fun TypeArgumentMarker.isStarProjection(): Boolean {