Relax requirements on function modifiers in multiplatform projects

Allow to implement header functions with external/tailrec/inline/infix/operator
functions

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/HeaderImplDeclarationChecker.kt

@@ -178,7 +178,8 @@ class HeaderImplDeclarationChecker(val moduleToCheck: ModuleDescriptor? = null)
 
             // Functions
 
-            object FunctionModifiers : Incompatible("modifiers are different (external, infix, inline, operator, suspend, tailrec)")
+            object FunctionModifiersDifferent : Incompatible("modifiers are different (suspend)")
+            object FunctionModifiersNotSubset : Incompatible("some modifiers on header declaration are missing on the implementation (external, infix, inline, operator, tailrec)")
 
             // Properties
 
@@ -273,9 +274,13 @@ class HeaderImplDeclarationChecker(val moduleToCheck: ModuleDescriptor? = null)
     }
 
     private fun areCompatibleFunctions(a: FunctionDescriptor, b: FunctionDescriptor): Compatibility {
-        if (!equalBy(a, b) { f ->
+        if (!equalBy(a, b) { f -> f.isSuspend }) return Incompatible.FunctionModifiersDifferent
-            listOf(f.isExternal, f.isInfix, f.isInline, f.isOperator, f.isSuspend, f.isTailrec)
+
-        }) return Incompatible.FunctionModifiers
+        if (a.isExternal && !b.isExternal ||
+            a.isInfix && !b.isInfix ||
+            a.isInline && !b.isInline ||
+            a.isOperator && !b.isOperator ||
+            a.isTailrec && !b.isTailrec) return Incompatible.FunctionModifiersNotSubset
 
         return Compatible
     }

compiler/testData/diagnostics/tests/multiplatform/topLevelFun/functionModifiers.kt

@@ -0,0 +1,19 @@
+// !LANGUAGE: +MultiPlatformProjects
+// !DIAGNOSTICS: -NOTHING_TO_INLINE
+// MODULE: m1-common
+// FILE: common.kt
+
+header fun external()
+header fun tailrec()
+header fun inline()
+header fun String.unaryMinus(): String
+header fun String.and(other: String): String
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+
+impl external fun external()
+impl tailrec fun tailrec(): Unit = if (true) Unit else tailrec()
+impl inline fun inline() {}
+impl operator fun String.unaryMinus(): String = this
+impl infix fun String.and(other: String): String = this + other

compiler/testData/diagnostics/tests/multiplatform/topLevelFun/functionModifiers.txt

@@ -0,0 +1,18 @@
+// -- Module: <m1-common> --
+package
+
+public header fun external(): kotlin.Unit
+public header fun inline(): kotlin.Unit
+public header fun tailrec(): kotlin.Unit
+public header fun kotlin.String.and(/*0*/ other: kotlin.String): kotlin.String
+public header fun kotlin.String.unaryMinus(): kotlin.String
+
+
+// -- Module: <m2-jvm> --
+package
+
+public external impl fun external(): kotlin.Unit
+public inline impl fun inline(): kotlin.Unit
+public tailrec impl fun tailrec(): kotlin.Unit
+public infix impl fun kotlin.String.and(/*0*/ other: kotlin.String): kotlin.String
+public operator impl fun kotlin.String.unaryMinus(): kotlin.String

compiler/testData/diagnostics/tests/multiplatform/topLevelFun/inlineFun.kt

@@ -15,4 +15,4 @@ impl fun nonInlineFun() { }
 // FILE: js.kt
 
 impl <!NOTHING_TO_INLINE!>inline<!> fun inlineFun() { }
-<!IMPLEMENTATION_WITHOUT_HEADER!>impl<!> <!NOTHING_TO_INLINE!>inline<!> fun nonInlineFun() { }
+impl <!NOTHING_TO_INLINE!>inline<!> fun nonInlineFun() { }

compiler/testData/multiplatform/incompatibleFunctions/common.kt

@@ -1,14 +1,9 @@
 header infix fun Int.plus(s: CharSequence): Int
-header fun Int.minus(s: String): Int
 
 header operator fun Double.times(x: CharArray)
-header fun Double.divide(x: ByteArray)
 
 header external fun f1()
-header fun g1()
 
 header inline fun f2()
-header fun g2()
 
 header tailrec fun f3()
-header fun g3()

compiler/testData/multiplatform/incompatibleFunctions/jvm.kt

@@ -1,14 +1,9 @@
 impl fun Int.plus(s: CharSequence): Int = 0
-impl infix fun Int.minus(s: String): Int = 1
 
 impl fun Double.times(x: CharArray) {}
-impl operator fun Double.divide(x: ByteArray) {}
 
 impl fun f1() {}
-impl external fun g1()
 
 impl fun f2() {}
-impl inline fun g2() {}
 
 impl fun f3() {}
-impl tailrec fun g3() {}

compiler/testData/multiplatform/incompatibleFunctions/output.txt

@@ -6,96 +6,48 @@ Output:
 Exit code: COMPILATION_ERROR
 Output:
 compiler/testData/multiplatform/incompatibleFunctions/common.kt:1:1: error: header declaration 'plus' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
+The following declaration is incompatible because some modifiers on header declaration are missing on the implementation (external, infix, inline, operator, tailrec):
     public impl fun Int.plus(s: CharSequence): Int
 
 header infix fun Int.plus(s: CharSequence): Int
 ^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:2:1: error: header declaration 'minus' has no implementation in module
+compiler/testData/multiplatform/incompatibleFunctions/common.kt:3:1: error: header declaration 'times' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
+The following declaration is incompatible because some modifiers on header declaration are missing on the implementation (external, infix, inline, operator, tailrec):
-    public infix impl fun Int.minus(s: String): Int
-
-header fun Int.minus(s: String): Int
-^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:4:1: error: header declaration 'times' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
     public impl fun Double.times(x: CharArray): Unit
 
 header operator fun Double.times(x: CharArray)
 ^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:5:1: error: header declaration 'divide' has no implementation in module
+compiler/testData/multiplatform/incompatibleFunctions/common.kt:5:1: error: header declaration 'f1' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
+The following declaration is incompatible because some modifiers on header declaration are missing on the implementation (external, infix, inline, operator, tailrec):
-    public operator impl fun Double.divide(x: ByteArray): Unit
-
-header fun Double.divide(x: ByteArray)
-^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:7:1: error: header declaration 'f1' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
     public impl fun f1(): Unit
 
 header external fun f1()
 ^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:8:1: error: header declaration 'g1' has no implementation in module
+compiler/testData/multiplatform/incompatibleFunctions/common.kt:7:1: error: header declaration 'f2' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
+The following declaration is incompatible because some modifiers on header declaration are missing on the implementation (external, infix, inline, operator, tailrec):
-    public external impl fun g1(): Unit
-
-header fun g1()
-^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:10:1: error: header declaration 'f2' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
     public impl fun f2(): Unit
 
 header inline fun f2()
 ^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:11:1: error: header declaration 'g2' has no implementation in module
+compiler/testData/multiplatform/incompatibleFunctions/common.kt:9:1: error: header declaration 'f3' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
+The following declaration is incompatible because some modifiers on header declaration are missing on the implementation (external, infix, inline, operator, tailrec):
-    public inline impl fun g2(): Unit
-
-header fun g2()
-^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:13:1: error: header declaration 'f3' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
     public impl fun f3(): Unit
 
 header tailrec fun f3()
 ^
-compiler/testData/multiplatform/incompatibleFunctions/common.kt:14:1: error: header declaration 'g3' has no implementation in module
-The following declaration is incompatible because modifiers are different (external, infix, inline, operator, suspend, tailrec):
-    public tailrec impl fun g3(): Unit
-
-header fun g3()
-^
 compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:1:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
 impl fun Int.plus(s: CharSequence): Int = 0
 ^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:2:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
+compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:3:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
-impl infix fun Int.minus(s: String): Int = 1
-^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:4:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
 impl fun Double.times(x: CharArray) {}
 ^
 compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:5:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
-impl operator fun Double.divide(x: ByteArray) {}
-^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:5:6: error: 'operator' modifier is inapplicable on this function: illegal function name
-impl operator fun Double.divide(x: ByteArray) {}
-     ^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:7:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
 impl fun f1() {}
 ^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:8:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
+compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:7:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
-impl external fun g1()
-^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:10:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
 impl fun f2() {}
 ^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:11:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
+compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:9:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
-impl inline fun g2() {}
-^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:13:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
 impl fun f3() {}
 ^
-compiler/testData/multiplatform/incompatibleFunctions/jvm.kt:14:1: error: modifier 'impl' is only applicable to members that are initially declared in platform-independent code
-impl tailrec fun g3() {}
-^
 

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

@@ -13149,6 +13149,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("functionModifiers.kt")
+                public void testFunctionModifiers() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/topLevelFun/functionModifiers.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("headerAndImplInDIfferentPackages.kt")
                 public void testHeaderAndImplInDIfferentPackages() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/topLevelFun/headerAndImplInDIfferentPackages.kt");