Don't try parsing contract-like function not from kotlin package

Returning `null` from `doCheckContract` functions means that we
have failed to parse contract function and should report an error, but
if the called function isn't true contract, we shouldn't evaluate that code
at all.

 #KT-27758 Fixed

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

@@ -34,29 +34,43 @@ import org.jetbrains.kotlin.resolve.scopes.LexicalScope
 import org.jetbrains.kotlin.resolve.scopes.LexicalScopeKind
 
 class ContractParsingServices(val languageVersionSettings: LanguageVersionSettings) {
+    /**
+     * ! IMPORTANT NOTICE !
+     *
+     * This function has very important non-obvious implicit contract:
+     * it *must* call [org.jetbrains.kotlin.contracts.description.LazyContractProvider.setContractDescription]
+     * if FunctionDescriptor had [LazyContractProvider] in the user data.
+     *
+     * Otherwise, it may lead to inconsistent resolve state and failed assertions
+     */
     fun checkContractAndRecordIfPresent(expression: KtExpression, trace: BindingTrace, scope: LexicalScope, isFirstStatement: Boolean) {
-        if (!expression.isContractDescriptionCallPsiCheck()) return // fastpath
+        // Fastpath. Note that it doesn't violates invariant described in KDoc, because 'isContractDescriptionCallPsiCheck'
+        // is a *necessary* (but not sufficient, actually) condition for presence of 'LazyContractProvider'
+        if (!expression.isContractDescriptionCallPsiCheck()) return
 
         val collector = TraceBasedCollector(trace, expression)
         val callContext = ContractCallContext(expression, isFirstStatement, scope, trace.bindingContext)
+        val contractProviderIfAny = (scope.ownerDescriptor as? FunctionDescriptor)?.getUserData(ContractProviderKey)
+
+        if (!callContext.isContractDescriptionCallPreciseCheck()) {
+            contractProviderIfAny?.setContractDescription(null)
+            return
+        }
+
         val parsedContract = doCheckContract(collector, callContext)
 
         collector.flushDiagnostics(parsingFailed = parsedContract == null)
 
-        val contractProviderIfAny = (scope.ownerDescriptor as? FunctionDescriptor)?.getUserData(ContractProviderKey)
-
         if (collector.hasErrors())
             contractProviderIfAny?.setContractDescription(null)
         else
             contractProviderIfAny?.setContractDescription(parsedContract)
     }
 
+    private fun ContractCallContext.isContractDescriptionCallPreciseCheck(): Boolean =
+        contractCallExpression.isContractDescriptionCallPreciseCheck(bindingContext)
+
     private fun doCheckContract(collector: ContractParsingDiagnosticsCollector, callContext: ContractCallContext): ContractDescription? {
-        val expression = callContext.contractCallExpression
-        val bindingContext = callContext.bindingContext
-
-        if (!expression.isContractDescriptionCallPreciseCheck(bindingContext)) return null
-
         checkFeatureEnabled(collector)
         checkContractAllowedHere(collector, callContext)
 

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/callUsualContractFunction.kt

@@ -0,0 +1,42 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+package my
+
+// Accepts block, can't be distinguished from kotlin.contract without resolve
+fun contract(block: () -> Unit) {}
+
+// Accepts int, potentially can be distinguished from kotlin.contract by PSI,
+// but as of Kotlin 1.3.0, we don't do that
+fun contract(i: Int) {}
+
+fun doStuff() {}
+
+class SomeClass {
+
+    fun contract() {}
+
+    fun callMemberContractWithThis() {
+        this.contract()
+    }
+
+    fun callMemberContractWithoutThis() {
+        contract()
+    }
+
+    fun callTopLevelSamePsiInMember() {
+        contract { }
+    }
+}
+
+fun callTopLevelSamePsi() {
+    contract { }
+}
+
+fun callTopLevelDifferentPsi() {
+    contract(42)
+}
+
+fun callTopLevelSamePsiNotFirstStatement() {
+    doStuff()
+    contract { }
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/callUsualContractFunction.txt

@@ -0,0 +1,21 @@
+package
+
+package my {
+    public fun callTopLevelDifferentPsi(): kotlin.Unit
+    public fun callTopLevelSamePsi(): kotlin.Unit
+    public fun callTopLevelSamePsiNotFirstStatement(): kotlin.Unit
+    public fun contract(/*0*/ block: () -> kotlin.Unit): kotlin.Unit
+    public fun contract(/*0*/ i: kotlin.Int): kotlin.Unit
+    public fun doStuff(): kotlin.Unit
+
+    public final class SomeClass {
+        public constructor SomeClass()
+        public final fun callMemberContractWithThis(): kotlin.Unit
+        public final fun callMemberContractWithoutThis(): kotlin.Unit
+        public final fun callTopLevelSamePsiInMember(): kotlin.Unit
+        public final fun contract(): kotlin.Unit
+        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/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java

@@ -1112,6 +1112,11 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
                 KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.ANY, true);
             }
 
+            @TestMetadata("callUsualContractFunction.kt")
+            public void testCallUsualContractFunction() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/callUsualContractFunction.kt");
+            }
+
             @TestMetadata("useBeforeDeclaration.kt")
             public void testUseBeforeDeclaration() throws Exception {
                 runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/useBeforeDeclaration.kt");

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

@@ -1112,6 +1112,11 @@ public class DiagnosticsTestWithStdLibUsingJavacGenerated extends AbstractDiagno
                 KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.ANY, true);
             }
 
+            @TestMetadata("callUsualContractFunction.kt")
+            public void testCallUsualContractFunction() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/callUsualContractFunction.kt");
+            }
+
             @TestMetadata("useBeforeDeclaration.kt")
             public void testUseBeforeDeclaration() throws Exception {
                 runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/useBeforeDeclaration.kt");