FIC: Parse fun keyword in front of interface as a modifier

compiler/psi/src/org/jetbrains/kotlin/lexer/KtTokens.java

@@ -57,7 +57,7 @@ public interface KtTokens {
     KtKeywordToken SUPER_KEYWORD            = KtKeywordToken.keyword("super");
     KtKeywordToken VAL_KEYWORD              = KtKeywordToken.keyword("val");
     KtKeywordToken VAR_KEYWORD              = KtKeywordToken.keyword("var");
-    KtKeywordToken FUN_KEYWORD              = KtKeywordToken.keyword("fun");
+    KtModifierKeywordToken FUN_KEYWORD      = KtModifierKeywordToken.keywordModifier("fun");
     KtKeywordToken FOR_KEYWORD              = KtKeywordToken.keyword("for");
     KtKeywordToken NULL_KEYWORD             = KtKeywordToken.keyword("null");
     KtKeywordToken TRUE_KEYWORD             = KtKeywordToken.keyword("true");
@@ -229,7 +229,7 @@ public interface KtTokens {
                     REIFIED_KEYWORD, COMPANION_KEYWORD, SEALED_KEYWORD, LATEINIT_KEYWORD,
                     DATA_KEYWORD, INLINE_KEYWORD, NOINLINE_KEYWORD, TAILREC_KEYWORD, EXTERNAL_KEYWORD, ANNOTATION_KEYWORD, CROSSINLINE_KEYWORD,
                     CONST_KEYWORD, OPERATOR_KEYWORD, INFIX_KEYWORD, SUSPEND_KEYWORD,
-                    HEADER_KEYWORD, IMPL_KEYWORD, EXPECT_KEYWORD, ACTUAL_KEYWORD
+                    HEADER_KEYWORD, IMPL_KEYWORD, EXPECT_KEYWORD, ACTUAL_KEYWORD, FUN_KEYWORD
             };
 
     TokenSet MODIFIER_KEYWORDS = TokenSet.create(MODIFIER_KEYWORDS_ARRAY);

compiler/psi/src/org/jetbrains/kotlin/parsing/KotlinParsing.java

@@ -51,9 +51,15 @@ public class KotlinParsing extends AbstractKotlinParsing {
     private static final TokenSet TYPE_REF_FIRST = TokenSet.create(LBRACKET, IDENTIFIER, LPAR, HASH, DYNAMIC_KEYWORD);
     private static final TokenSet RECEIVER_TYPE_TERMINATORS = TokenSet.create(DOT, SAFE_ACCESS);
     private static final TokenSet VALUE_PARAMETER_FIRST =
-            TokenSet.orSet(TokenSet.create(IDENTIFIER, LBRACKET, VAL_KEYWORD, VAR_KEYWORD), MODIFIER_KEYWORDS);
+            TokenSet.orSet(
+                    TokenSet.create(IDENTIFIER, LBRACKET, VAL_KEYWORD, VAR_KEYWORD),
+                    TokenSet.andNot(MODIFIER_KEYWORDS, TokenSet.create(FUN_KEYWORD))
+            );
     private static final TokenSet LAMBDA_VALUE_PARAMETER_FIRST =
-            TokenSet.orSet(TokenSet.create(IDENTIFIER, LBRACKET), MODIFIER_KEYWORDS);
+            TokenSet.orSet(
+                    TokenSet.create(IDENTIFIER, LBRACKET),
+                    TokenSet.andNot(MODIFIER_KEYWORDS, TokenSet.create(FUN_KEYWORD))
+            );
     private static final TokenSet SOFT_KEYWORDS_AT_MEMBER_START = TokenSet.create(CONSTRUCTOR_KEYWORD, INIT_KEYWORD);
     private static final TokenSet ANNOTATION_TARGETS = TokenSet.create(
             FILE_KEYWORD, FIELD_KEYWORD, GET_KEYWORD, SET_KEYWORD, PROPERTY_KEYWORD,
@@ -585,6 +591,12 @@ public class KotlinParsing extends AbstractKotlinParsing {
 
         if (atSet(modifierKeywords)) {
             IElementType lookahead = lookahead(1);
+
+            if (at(FUN_KEYWORD) && lookahead != INTERFACE_KEYWORD) {
+                marker.rollbackTo();
+                return false;
+            }
+
             if (lookahead != null && !noModifiersBefore.contains(lookahead)) {
                 IElementType tt = tt();
                 if (tokenConsumer != null) {

compiler/testData/psi/kotlinFunInterface_ERR.kt

@@ -0,0 +1,11 @@
+interface fun Foo
+
+fun private interface Foo
+
+fun @Bar interface Foo
+
+fun class Foo
+
+fun abstract class Foo
+
+fun object Foo

compiler/testData/psi/kotlinFunInterface_ERR.txt

@@ -0,0 +1,79 @@
+KtFile: kotlinFunInterface_ERR.kt
+  PACKAGE_DIRECTIVE
+    <empty list>
+  IMPORT_LIST
+    <empty list>
+  CLASS
+    PsiElement(interface)('interface')
+    PsiErrorElement:Name expected
+      <empty list>
+  PsiWhiteSpace(' ')
+  FUN
+    PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+    PsiErrorElement:Expecting '('
+      <empty list>
+  PsiWhiteSpace('\n\n')
+  FUN
+    PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('private')
+    PsiErrorElement:Expecting '('
+      <empty list>
+  PsiWhiteSpace(' ')
+  CLASS
+    PsiElement(interface)('interface')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+  PsiWhiteSpace('\n\n')
+  FUN
+    PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiErrorElement:Annotations are not allowed in this position
+      ANNOTATION_ENTRY
+        PsiElement(AT)('@')
+        CONSTRUCTOR_CALLEE
+          TYPE_REFERENCE
+            USER_TYPE
+              REFERENCE_EXPRESSION
+                PsiElement(IDENTIFIER)('Bar')
+    PsiErrorElement:Expecting function name or receiver type
+      <empty list>
+  PsiWhiteSpace(' ')
+  CLASS
+    PsiElement(interface)('interface')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+  PsiWhiteSpace('\n\n')
+  FUN
+    PsiElement(fun)('fun')
+    PsiErrorElement:Expecting function name or receiver type
+      <empty list>
+  PsiWhiteSpace(' ')
+  CLASS
+    PsiElement(class)('class')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+  PsiWhiteSpace('\n\n')
+  FUN
+    PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('abstract')
+    PsiErrorElement:Expecting '('
+      <empty list>
+  PsiWhiteSpace(' ')
+  CLASS
+    PsiElement(class)('class')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+  PsiWhiteSpace('\n\n')
+  FUN
+    PsiElement(fun)('fun')
+    PsiErrorElement:Expecting function name or receiver type
+      <empty list>
+  PsiWhiteSpace(' ')
+  OBJECT_DECLARATION
+    PsiElement(object)('object')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')

compiler/testData/psi/validKotlinFunInterface.kt

@@ -0,0 +1,17 @@
+fun interface Foo
+
+fun interface Foo {
+    fun invoke()
+}
+
+private fun interface Foo
+
+@Bar
+fun interface Foo
+
+class TopLevel {
+    fun interface Foo
+}
+
+fun
+interface Foo

compiler/testData/psi/validKotlinFunInterface.txt

@@ -0,0 +1,85 @@
+KtFile: validKotlinFunInterface.kt
+  PACKAGE_DIRECTIVE
+    <empty list>
+  IMPORT_LIST
+    <empty list>
+  CLASS
+    MODIFIER_LIST
+      PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiElement(interface)('interface')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+  PsiWhiteSpace('\n\n')
+  CLASS
+    MODIFIER_LIST
+      PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiElement(interface)('interface')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+    PsiWhiteSpace(' ')
+    CLASS_BODY
+      PsiElement(LBRACE)('{')
+      PsiWhiteSpace('\n    ')
+      FUN
+        PsiElement(fun)('fun')
+        PsiWhiteSpace(' ')
+        PsiElement(IDENTIFIER)('invoke')
+        VALUE_PARAMETER_LIST
+          PsiElement(LPAR)('(')
+          PsiElement(RPAR)(')')
+      PsiWhiteSpace('\n')
+      PsiElement(RBRACE)('}')
+  PsiWhiteSpace('\n\n')
+  CLASS
+    MODIFIER_LIST
+      PsiElement(private)('private')
+      PsiWhiteSpace(' ')
+      PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiElement(interface)('interface')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+  PsiWhiteSpace('\n\n')
+  CLASS
+    MODIFIER_LIST
+      ANNOTATION_ENTRY
+        PsiElement(AT)('@')
+        CONSTRUCTOR_CALLEE
+          TYPE_REFERENCE
+            USER_TYPE
+              REFERENCE_EXPRESSION
+                PsiElement(IDENTIFIER)('Bar')
+      PsiWhiteSpace('\n')
+      PsiElement(fun)('fun')
+    PsiWhiteSpace(' ')
+    PsiElement(interface)('interface')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')
+  PsiWhiteSpace('\n\n')
+  CLASS
+    PsiElement(class)('class')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('TopLevel')
+    PsiWhiteSpace(' ')
+    CLASS_BODY
+      PsiElement(LBRACE)('{')
+      PsiWhiteSpace('\n    ')
+      CLASS
+        MODIFIER_LIST
+          PsiElement(fun)('fun')
+        PsiWhiteSpace(' ')
+        PsiElement(interface)('interface')
+        PsiWhiteSpace(' ')
+        PsiElement(IDENTIFIER)('Foo')
+      PsiWhiteSpace('\n')
+      PsiElement(RBRACE)('}')
+  PsiWhiteSpace('\n\n')
+  CLASS
+    MODIFIER_LIST
+      PsiElement(fun)('fun')
+    PsiWhiteSpace('\n')
+    PsiElement(interface)('interface')
+    PsiWhiteSpace(' ')
+    PsiElement(IDENTIFIER)('Foo')

compiler/tests/org/jetbrains/kotlin/parsing/ParsingTestGenerated.java

@@ -450,6 +450,11 @@ public class ParsingTestGenerated extends AbstractParsingTest {
             runTest("compiler/testData/psi/InterfaceWithEnumKeyword.kt");
         }
 
+        @TestMetadata("kotlinFunInterface_ERR.kt")
+        public void testKotlinFunInterface_ERR() throws Exception {
+            runTest("compiler/testData/psi/kotlinFunInterface_ERR.kt");
+        }
+
         @TestMetadata("Labels.kt")
         public void testLabels() throws Exception {
             runTest("compiler/testData/psi/Labels.kt");
@@ -715,6 +720,11 @@ public class ParsingTestGenerated extends AbstractParsingTest {
             runTest("compiler/testData/psi/UnsignedLiteral.kt");
         }
 
+        @TestMetadata("validKotlinFunInterface.kt")
+        public void testValidKotlinFunInterface() throws Exception {
+            runTest("compiler/testData/psi/validKotlinFunInterface.kt");
+        }
+
         @TestMetadata("When.kt")
         public void testWhen() throws Exception {
             runTest("compiler/testData/psi/When.kt");