Support platform/impl modifiers for functions

Also add a new capability for ModuleDescriptor, which is used to obtain the
platform in the multi-platform scenario in tests.

Suppress the following errors for platform functions: "function has no body"
and "nothing to inline". Also do not report redeclaration between platform and
non-platform functions because this is the case when the common +
platform-specific code are analyzed together.

Note that some diagnostics reported in tests are not yet implemented in this
commit, they appear in subsequent commits

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

@@ -0,0 +1,25 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+platform fun foo(x: Int): Int
+
+fun callFromCommonCode(x: Int) = foo(x)
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+
+impl fun foo(x: Int): Int {
+    return x + 1
+}
+
+fun callFromJVM(x: Int) = foo(x)
+
+// MODULE: m3-js(m1-common)
+// FILE: js.kt
+
+impl fun foo(x: Int): Int {
+    return x - 1
+}
+
+fun callFromJS(x: Int) = foo(x)

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

@@ -0,0 +1,21 @@
+// -- Module: <m1-common> --
+package
+
+public fun callFromCommonCode(/*0*/ x: kotlin.Int): kotlin.Int
+public platform fun foo(/*0*/ x: kotlin.Int): kotlin.Int
+
+
+// -- Module: <m2-jvm> --
+package
+
+public fun callFromCommonCode(/*0*/ x: kotlin.Int): kotlin.Int
+public fun callFromJVM(/*0*/ x: kotlin.Int): kotlin.Int
+public impl fun foo(/*0*/ x: kotlin.Int): kotlin.Int
+
+
+// -- Module: <m3-js> --
+package
+
+public fun callFromCommonCode(/*0*/ x: kotlin.Int): kotlin.Int
+public fun callFromJS(/*0*/ x: kotlin.Int): kotlin.Int
+public impl fun foo(/*0*/ x: kotlin.Int): kotlin.Int

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

@@ -0,0 +1,8 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+<!CONFLICTING_OVERLOADS!>platform fun foo()<!>
+<!CONFLICTING_OVERLOADS!>platform fun foo()<!>
+
+platform fun foo(x: Int)

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

@@ -0,0 +1,5 @@
+package
+
+public platform fun foo(): kotlin.Unit
+public platform fun foo(): kotlin.Unit
+public platform fun foo(/*0*/ x: kotlin.Int): kotlin.Unit

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

@@ -0,0 +1,17 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+platform fun foo()
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+
+<!CONFLICTING_OVERLOADS!>impl fun foo()<!> {}
+<!CONFLICTING_OVERLOADS!>impl fun foo()<!> {}
+
+// MODULE: m3-js(m1-common)
+// FILE: js.kt
+
+<!CONFLICTING_OVERLOADS!>impl fun foo()<!> {}
+<!CONFLICTING_OVERLOADS!>impl fun foo()<!> {}

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

@@ -0,0 +1,18 @@
+// -- Module: <m1-common> --
+package
+
+public platform fun foo(): kotlin.Unit
+
+
+// -- Module: <m2-jvm> --
+package
+
+public impl fun foo(): kotlin.Unit
+public impl fun foo(): kotlin.Unit
+
+
+// -- Module: <m3-js> --
+package
+
+public impl fun foo(): kotlin.Unit
+public impl fun foo(): kotlin.Unit

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

@@ -0,0 +1,18 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+package common
+
+platform fun foo()
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+package jvm
+
+<!PLATFORM_DEFINITION_WITHOUT_DECLARATION!>impl<!> fun foo() {}
+
+// MODULE: m3-js(m1-common)
+// FILE: js.kt
+package js
+
+<!PLATFORM_DEFINITION_WITHOUT_DECLARATION!>impl<!> fun foo() {}

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

@@ -0,0 +1,28 @@
+// -- Module: <m1-common> --
+package
+
+package common {
+    public platform fun foo(): kotlin.Unit
+}
+
+
+// -- Module: <m2-jvm> --
+package
+
+package common {
+}
+
+package jvm {
+    public impl fun foo(): kotlin.Unit
+}
+
+
+// -- Module: <m3-js> --
+package
+
+package common {
+}
+
+package js {
+    public impl fun foo(): kotlin.Unit
+}

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

@@ -0,0 +1,5 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+platform fun foo()

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

@@ -0,0 +1,3 @@
+package
+
+public platform fun foo(): kotlin.Unit

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

@@ -0,0 +1,5 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+platform fun foo(x: Int, <!PLATFORM_DECLARATION_WITH_DEFAULT_PARAMETER!>y: String = ""<!>)

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

@@ -0,0 +1,3 @@
+package
+
+public platform fun foo(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.String = ...): kotlin.Unit

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

@@ -0,0 +1,5 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-jvm
+// FILE: jvm.kt
+
+<!PLATFORM_DEFINITION_WITHOUT_DECLARATION!>impl<!> fun foo() { }

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

@@ -0,0 +1,3 @@
+package
+
+public impl fun foo(): kotlin.Unit

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

@@ -0,0 +1,18 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+inline platform fun inlineFun()
+platform fun nonInlineFun()
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+
+<!PLATFORM_DEFINITION_WITHOUT_DECLARATION!>impl<!> fun inlineFun() { }
+impl fun nonInlineFun() { }
+
+// MODULE: m3-js(m1-common)
+// FILE: js.kt
+
+impl <!NOTHING_TO_INLINE!>inline<!> fun inlineFun() { }
+<!PLATFORM_DEFINITION_WITHOUT_DECLARATION!>impl<!> <!NOTHING_TO_INLINE!>inline<!> fun nonInlineFun() { }

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

@@ -0,0 +1,19 @@
+// -- Module: <m1-common> --
+package
+
+public inline platform fun inlineFun(): kotlin.Unit
+public platform fun nonInlineFun(): kotlin.Unit
+
+
+// -- Module: <m2-jvm> --
+package
+
+public impl fun inlineFun(): kotlin.Unit
+public impl fun nonInlineFun(): kotlin.Unit
+
+
+// -- Module: <m3-js> --
+package
+
+public inline impl fun inlineFun(): kotlin.Unit
+public inline impl fun nonInlineFun(): kotlin.Unit

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

@@ -0,0 +1,9 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+<!CONFLICTING_OVERLOADS!>platform fun foo()<!>
+
+<!CONFLICTING_OVERLOADS, PLATFORM_DECLARATION_WITH_BODY!>platform fun foo()<!> {}
+
+<!PLATFORM_DECLARATION_WITH_BODY!>platform fun bar()<!> {}

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

@@ -0,0 +1,5 @@
+package
+
+public platform fun bar(): kotlin.Unit
+public platform fun foo(): kotlin.Unit
+public platform fun foo(): kotlin.Unit

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

@@ -0,0 +1,12 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+platform fun foo()
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+
+<!NON_MEMBER_FUNCTION_NO_BODY!>impl fun foo()<!>
+
+<!NON_MEMBER_FUNCTION_NO_BODY!><!PLATFORM_DEFINITION_WITHOUT_DECLARATION!>impl<!> fun bar()<!>

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

@@ -0,0 +1,11 @@
+// -- Module: <m1-common> --
+package
+
+public platform fun foo(): kotlin.Unit
+
+
+// -- Module: <m2-jvm> --
+package
+
+public impl fun bar(): kotlin.Unit
+public impl fun foo(): kotlin.Unit

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

@@ -0,0 +1,12 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+platform fun foo()
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+impl fun foo() {}
+
+// MODULE: m3-js(m1-common)
+// FILE: js.kt
+impl fun foo() {}

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

@@ -0,0 +1,16 @@
+// -- Module: <m1-common> --
+package
+
+public platform fun foo(): kotlin.Unit
+
+
+// -- Module: <m2-jvm> --
+package
+
+public impl fun foo(): kotlin.Unit
+
+
+// -- Module: <m3-js> --
+package
+
+public impl fun foo(): kotlin.Unit