FIR: Consider abbreviation's nullability when expanding types

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ResolveUtils.kt

@@ -98,11 +98,17 @@ fun ConeClassLikeType.directExpansionType(
         .toSymbol(useSiteSession)
         ?.safeAs<FirTypeAliasSymbol>()?.fir ?: return null
 
-    val resultType = expandedConeType(typeAlias) ?: return null
+    val resultType = expandedConeType(typeAlias)?.applyNullabilityFrom(this) ?: return null
+
     if (resultType.typeArguments.isEmpty()) return resultType
     return mapTypeAliasArguments(typeAlias, this, resultType) as? ConeClassLikeType
 }
 
+private fun ConeClassLikeType.applyNullabilityFrom(abbreviation: ConeClassLikeType): ConeClassLikeType {
+    if (abbreviation.isMarkedNullable) return withNullability(ConeNullability.NULLABLE)
+    return this
+}
+
 private fun mapTypeAliasArguments(
     typeAlias: FirTypeAlias,
     abbreviatedType: ConeClassLikeType,

compiler/fir/resolve/testData/resolve/stdlib/concurrentMapOfAliases.kt

@@ -0,0 +1,12 @@
+// FULL_JDK
+private typealias MyAlias = CharSequence
+
+class A {
+    private val foo = java.util.concurrent.ConcurrentHashMap<String, MyAlias>()
+
+    private fun bar() {
+        foo["dd"]?.baz()
+    }
+
+    private fun MyAlias.baz() {}
+}

compiler/fir/resolve/testData/resolve/stdlib/concurrentMapOfAliases.txt

@@ -0,0 +1,18 @@
+FILE: concurrentMapOfAliases.kt
+    private final typealias MyAlias = R|kotlin/CharSequence|
+    public final class A : R|kotlin/Any| {
+        public constructor(): R|A| {
+            super<R|kotlin/Any|>()
+        }
+
+        private final val foo: R|java/util/concurrent/ConcurrentHashMap<kotlin/String, kotlin/CharSequence>| = Q|java/util/concurrent|.R|java/util/concurrent/ConcurrentHashMap.ConcurrentHashMap|<R|kotlin/String|, R|kotlin/CharSequence|>()
+            private get(): R|java/util/concurrent/ConcurrentHashMap<kotlin/String, kotlin/CharSequence>|
+
+        private final fun bar(): R|kotlin/Unit| {
+            (this@R|/A|, this@R|/A|.R|/A.foo|.R|FakeOverride<java/util/concurrent/ConcurrentHashMap.get: R|kotlin/CharSequence?|>|(String(dd)))?.R|/A.baz|()
+        }
+
+        private final fun R|MyAlias|.baz(): R|kotlin/Unit| {
+        }
+
+    }

compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithStdlibTestGenerated.java

@@ -78,6 +78,11 @@ public class FirDiagnosticsWithStdlibTestGenerated extends AbstractFirDiagnostic
         runTest("compiler/fir/resolve/testData/resolve/stdlib/concurrent.kt");
     }
 
+    @TestMetadata("concurrentMapOfAliases.kt")
+    public void testConcurrentMapOfAliases() throws Exception {
+        runTest("compiler/fir/resolve/testData/resolve/stdlib/concurrentMapOfAliases.kt");
+    }
+
     @TestMetadata("emptyArray.kt")
     public void testEmptyArray() throws Exception {
         runTest("compiler/fir/resolve/testData/resolve/stdlib/emptyArray.kt");

compiler/testData/diagnostics/tests/inference/regressions/kt702.fir.kt

@@ -13,8 +13,8 @@ public class Throwables() {
             }
         }
         public fun propagateIfPossible(throwable : Throwable?) : Unit {
-            <!INAPPLICABLE_CANDIDATE!>propagateIfInstanceOf<!>(throwable, getJavaClass<Error?>()) // Type inference failed: Mismatch while expanding constraints
+            propagateIfInstanceOf(throwable, getJavaClass<Error?>()) // Type inference failed: Mismatch while expanding constraints
-            <!INAPPLICABLE_CANDIDATE!>propagateIfInstanceOf<!>(throwable, getJavaClass<RuntimeException?>()) // Type inference failed: Mismatch while expanding constraints
+            propagateIfInstanceOf(throwable, getJavaClass<RuntimeException?>()) // Type inference failed: Mismatch while expanding constraints
         }
     }
-}
+}

compiler/testData/diagnostics/tests/regressions/kt701.fir.kt

@@ -10,8 +10,8 @@ public class Throwables() {
             }
         }
         public fun propagateIfPossible(throwable : Throwable?) {
-            <!INAPPLICABLE_CANDIDATE!>propagateIfInstanceOf<!>(throwable, getJavaClass<Error?>()) //; Type inference failed: Mismatch while expanding constraints
+            propagateIfInstanceOf(throwable, getJavaClass<Error?>()) //; Type inference failed: Mismatch while expanding constraints
-            <!INAPPLICABLE_CANDIDATE!>propagateIfInstanceOf<!>(throwable, getJavaClass<RuntimeException?>()) // Type inference failed: Mismatch while expanding constraints
+            propagateIfInstanceOf(throwable, getJavaClass<RuntimeException?>()) // Type inference failed: Mismatch while expanding constraints
         }
     }
-}
+}

compiler/testData/diagnostics/tests/typealias/inGenerics.fir.kt

@@ -9,4 +9,4 @@ val ms: MyString = "MyString"
 val msn: MyString? = null
 
 val msc: MyStringContainer = Container(ms)
-val msc1 = <!INAPPLICABLE_CANDIDATE!>MyStringContainer<!>(null)
+val msc1 = MyStringContainer(null)