Prohibit using references to this from outer scope in contract declarations

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

@@ -1174,6 +1174,11 @@ public class FirOldFrontendDiagnosticsTestWithStdlibGenerated extends AbstractFi
                     KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
                 }
 
+                @TestMetadata("accessToOuterThis.kt")
+                public void testAccessToOuterThis() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/accessToOuterThis.kt");
+                }
+
                 public void testAllFilesPresentInErrors() throws Exception {
                     KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors"), Pattern.compile("^(.+)\\.kt$"), Pattern.compile("^(.+)\\.fir\\.kts?$"), true);
                 }

compiler/frontend/src/org/jetbrains/kotlin/contracts/parsing/PsiContractParserDispatcher.kt

@@ -133,9 +133,18 @@ internal class PsiContractParserDispatcher(
             return null
         }
 
-        if (descriptor is ReceiverParameterDescriptor && descriptor.type.constructor.declarationDescriptor?.isFromContractDsl() == true) {
-            collector.badDescription("only references to parameters are allowed. Did you miss label on <this>?", expression)
-            return null
+        if (descriptor is ReceiverParameterDescriptor) {
+            if (descriptor.type.constructor.declarationDescriptor?.isFromContractDsl() == true) {
+                collector.badDescription("only references to parameters are allowed. Did you miss label on <this>?", expression)
+                return null
+            }
+            val directReceiver = callContext.functionDescriptor.let {
+                it.extensionReceiverParameter ?: it.dispatchReceiverParameter
+            }
+            if (descriptor != directReceiver) {
+                collector.badDescription("only references to direct <this> are allowed", expression)
+                return null
+            }
         }
 
         return if (KotlinBuiltIns.isBoolean(descriptor.type))

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/accessToOuterThis.fir.kt

@@ -0,0 +1,41 @@
+// !LANGUAGE: +AllowContractsForCustomFunctions +UseReturnsEffect +AllowContractsForNonOverridableMembers
+// !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER -SENSELESS_COMPARISON
+
+import kotlin.contracts.*
+
+interface A
+
+class Foo {
+    inner class Bar {
+        fun good() {
+            contract {
+                returns() implies (this@Bar != null)
+            }
+        }
+
+        fun badOuter() {
+            contract {
+                returns() implies (this@Foo != null)
+            }
+        }
+
+        fun badInner() {
+            contract {
+                returns() implies (this != null)
+            }
+        }
+
+        fun A?.goodWithReceiver() {
+            contract {
+                returns() implies (this@goodWithReceiver != null)
+            }
+        }
+
+        fun A?.badWithReceiver() {
+            contract {
+                returns() implies (this@Bar != null)
+            }
+        }
+    }
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/accessToOuterThis.kt

@@ -0,0 +1,41 @@
+// !LANGUAGE: +AllowContractsForCustomFunctions +UseReturnsEffect +AllowContractsForNonOverridableMembers
+// !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER -SENSELESS_COMPARISON
+
+import kotlin.contracts.*
+
+interface A
+
+class Foo {
+    inner class Bar {
+        fun good() {
+            contract {
+                returns() implies (this@Bar != null)
+            }
+        }
+
+        fun badOuter() {
+            contract {
+                returns() implies (<!ERROR_IN_CONTRACT_DESCRIPTION("only references to direct <this> are allowed")!>this@Foo<!> != null)
+            }
+        }
+
+        fun badInner() {
+            contract {
+                returns() implies (<!ERROR_IN_CONTRACT_DESCRIPTION("only references to parameters are allowed. Did you miss label on <this>?")!>this<!> != null)
+            }
+        }
+
+        fun A?.goodWithReceiver() {
+            contract {
+                returns() implies (this@goodWithReceiver != null)
+            }
+        }
+
+        fun A?.badWithReceiver() {
+            contract {
+                returns() implies (<!ERROR_IN_CONTRACT_DESCRIPTION("only references to direct <this> are allowed")!>this@Bar<!> != null)
+            }
+        }
+    }
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/accessToOuterThis.txt

@@ -0,0 +1,30 @@
+package
+
+public interface 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
+}
+
+public final class Foo {
+    public constructor Foo()
+    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 inner class Bar {
+        public constructor Bar()
+        public final fun badInner(): kotlin.Unit
+        public final fun badOuter(): kotlin.Unit
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final fun good(): kotlin.Unit
+            Returns(WILDCARD) -> <this> != null
+
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        public final fun A?.badWithReceiver(): kotlin.Unit
+        public final fun A?.goodWithReceiver(): kotlin.Unit
+            Returns(WILDCARD) -> <this> != null
+
+    }
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java

@@ -1175,6 +1175,11 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
                     KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
                 }
 
+                @TestMetadata("accessToOuterThis.kt")
+                public void testAccessToOuterThis() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/accessToOuterThis.kt");
+                }
+
                 public void testAllFilesPresentInErrors() throws Exception {
                     KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors"), Pattern.compile("^(.+)\\.kt$"), Pattern.compile("^(.+)\\.fir\\.kts?$"), true);
                 }

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsTestWithStdLibUsingJavacGenerated.java

@@ -1175,6 +1175,11 @@ public class DiagnosticsTestWithStdLibUsingJavacGenerated extends AbstractDiagno
                     KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
                 }
 
+                @TestMetadata("accessToOuterThis.kt")
+                public void testAccessToOuterThis() throws Exception {
+                    runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/accessToOuterThis.kt");
+                }
+
                 public void testAllFilesPresentInErrors() throws Exception {
                     KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors"), Pattern.compile("^(.+)\\.kt$"), Pattern.compile("^(.+)\\.fir\\.kts?$"), true);
                 }