[K2] Disallow named functions as expressions

^KT-62573 Fixed
^KT-59945 Fixed

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

@@ -3056,6 +3056,18 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.SINGLE_ANONYMOUS_FUNCTION_WITH_NAME.errorFactory) { firDiagnostic ->
+        SingleAnonymousFunctionWithNameErrorImpl(
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
+    add(FirErrors.SINGLE_ANONYMOUS_FUNCTION_WITH_NAME.warningFactory) { firDiagnostic ->
+        SingleAnonymousFunctionWithNameWarningImpl(
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.ANONYMOUS_FUNCTION_PARAMETER_WITH_DEFAULT_VALUE) { firDiagnostic ->
         AnonymousFunctionParameterWithDefaultValueImpl(
             firDiagnostic as KtPsiDiagnostic,

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

@@ -2164,6 +2164,14 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = AnonymousFunctionWithName::class
     }
 
+    interface SingleAnonymousFunctionWithNameError : KtFirDiagnostic<KtFunction> {
+        override val diagnosticClass get() = SingleAnonymousFunctionWithNameError::class
+    }
+
+    interface SingleAnonymousFunctionWithNameWarning : KtFirDiagnostic<KtFunction> {
+        override val diagnosticClass get() = SingleAnonymousFunctionWithNameWarning::class
+    }
+
     interface AnonymousFunctionParameterWithDefaultValue : KtFirDiagnostic<KtParameter> {
         override val diagnosticClass get() = AnonymousFunctionParameterWithDefaultValue::class
     }

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

@@ -2592,6 +2592,16 @@ internal class AnonymousFunctionWithNameImpl(
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<KtFunction>(firDiagnostic, token), KtFirDiagnostic.AnonymousFunctionWithName
 
+internal class SingleAnonymousFunctionWithNameErrorImpl(
+    firDiagnostic: KtPsiDiagnostic,
+    token: KtLifetimeToken,
+) : KtAbstractFirDiagnostic<KtFunction>(firDiagnostic, token), KtFirDiagnostic.SingleAnonymousFunctionWithNameError
+
+internal class SingleAnonymousFunctionWithNameWarningImpl(
+    firDiagnostic: KtPsiDiagnostic,
+    token: KtLifetimeToken,
+) : KtAbstractFirDiagnostic<KtFunction>(firDiagnostic, token), KtFirDiagnostic.SingleAnonymousFunctionWithNameWarning
+
 internal class AnonymousFunctionParameterWithDefaultValueImpl(
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java

@@ -9212,6 +9212,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                 runTest("compiler/testData/diagnostics/tests/declarationChecks/kt2643MultiDeclInControlFlow.kt");
             }
 
+            @Test
+            @TestMetadata("kt47245.kt")
+            public void testKt47245() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/declarationChecks/kt47245.kt");
+            }
+
             @Test
             @TestMetadata("kt559.kt")
             public void testKt559() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java

@@ -9212,6 +9212,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                 runTest("compiler/testData/diagnostics/tests/declarationChecks/kt2643MultiDeclInControlFlow.kt");
             }
 
+            @Test
+            @TestMetadata("kt47245.kt")
+            public void testKt47245() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/declarationChecks/kt47245.kt");
+            }
+
             @Test
             @TestMetadata("kt559.kt")
             public void testKt559() throws Exception {