Parsing: allow primary ctor in object syntactically

It's needed for better recovering for cases of changes like 'class' -> 'object'

The only sensible case when it's may be bad:
class A {
   object B
   constructor() : super()
}

But it seems to be rare, and ';' can be used to separate object from secondary ctor

compiler/frontend/src/org/jetbrains/kotlin/parsing/JetParsing.java

@@ -705,14 +705,18 @@ public class JetParsing extends AbstractJetParsing {
      * class
      *   : modifiers ("class" | "interface") SimpleName
      *       typeParameters?
-     *         modifiers ("(" primaryConstructorParameter{","} ")")?
+     *       primaryConstructor?
      *       (":" annotations delegationSpecifier{","})?
      *       typeConstraints
      *       (classBody? | enumClassBody)
      *   ;
      *
+     * primaryConstructor
+     *   : (modifiers "constructor")? ("(" functionParameter{","} ")")
+     *   ;
+     *
      * object
-     *   : "object" SimpleName? ":" delegationSpecifier{","}? classBody?
+     *   : "object" SimpleName? primaryConstructor? ":" delegationSpecifier{","}? classBody?
      *   ;
      */
     IElementType parseClassOrObject(
@@ -761,7 +765,7 @@ public class JetParsing extends AbstractJetParsing {
         );
 
         // Some modifiers found, but no parentheses following: class has already ended, and we are looking at something else
-        if ((object && at(CONSTRUCTOR_KEYWORD)) || (hasConstructorModifiers && !atSet(LPAR, LBRACE, COLON, CONSTRUCTOR_KEYWORD))) {
+        if (hasConstructorModifiers && !atSet(LPAR, LBRACE, COLON, CONSTRUCTOR_KEYWORD)) {
             beforeConstructorModifiers.rollbackTo();
             return object ? OBJECT_DECLARATION : CLASS;
         }

compiler/testData/psi/annotation/at/validDeclarations.kt

@@ -28,7 +28,7 @@ private @open [Ann1(1)] @Ann2("1") Ann3("2") class A(
 
     @companion object
 
-    @companion @private object B
+    @companion @private object B;
 
     @main
 

compiler/testData/psi/annotation/at/validDeclarations.txt

@@ -419,6 +419,7 @@ JetFile: validDeclarations.kt
         PsiWhiteSpace(' ')
         OBJECT_DECLARATION_NAME
           PsiElement(IDENTIFIER)('B')
+      PsiElement(SEMICOLON)(';')
       PsiWhiteSpace('\n\n    ')
       SECONDARY_CONSTRUCTOR
         MODIFIER_LIST

compiler/testData/psi/primaryConstructor/nestedClassAmbiguity.txt

@@ -127,17 +127,14 @@ JetFile: nestedClassAmbiguity.kt
         PsiWhiteSpace(' ')
         OBJECT_DECLARATION_NAME
           PsiElement(IDENTIFIER)('Nested4')
-      PsiWhiteSpace('\n    ')
-      SECONDARY_CONSTRUCTOR
-        PsiElement(constructor)('constructor')
-        VALUE_PARAMETER_LIST
-          PsiElement(LPAR)('(')
-          PsiElement(RPAR)(')')
+        PsiWhiteSpace('\n    ')
+        PRIMARY_CONSTRUCTOR
+          PsiElement(constructor)('constructor')
+          VALUE_PARAMETER_LIST
+            PsiElement(LPAR)('(')
+            PsiElement(RPAR)(')')
         PsiWhiteSpace(' ')
-        CONSTRUCTOR_DELEGATION_CALL
-          CONSTRUCTOR_DELEGATION_REFERENCE
-            <empty list>
-        BLOCK
+        CLASS_BODY
           PsiElement(LBRACE)('{')
           PsiElement(RBRACE)('}')
       PsiWhiteSpace('\n\n    ')
@@ -146,26 +143,29 @@ JetFile: nestedClassAmbiguity.kt
         PsiWhiteSpace(' ')
         OBJECT_DECLARATION_NAME
           PsiElement(IDENTIFIER)('Nested5')
-      PsiWhiteSpace(' ')
-      SECONDARY_CONSTRUCTOR
-        MODIFIER_LIST
-          PsiElement(private)('private')
         PsiWhiteSpace(' ')
-        PsiElement(constructor)('constructor')
-        VALUE_PARAMETER_LIST
-          PsiElement(LPAR)('(')
-          PsiElement(RPAR)(')')
-        PsiWhiteSpace(' ')
-        PsiElement(COLON)(':')
-        PsiWhiteSpace(' ')
-        CONSTRUCTOR_DELEGATION_CALL
-          CONSTRUCTOR_DELEGATION_REFERENCE
-            PsiElement(super)('super')
-          VALUE_ARGUMENT_LIST
+        PRIMARY_CONSTRUCTOR
+          MODIFIER_LIST
+            PsiElement(private)('private')
+          PsiWhiteSpace(' ')
+          PsiElement(constructor)('constructor')
+          VALUE_PARAMETER_LIST
             PsiElement(LPAR)('(')
             PsiElement(RPAR)(')')
         PsiWhiteSpace(' ')
-        BLOCK
+        PsiElement(COLON)(':')
+        PsiWhiteSpace(' ')
+        DELEGATION_SPECIFIER_LIST
+          DELEGATOR_SUPER_CALL
+            CONSTRUCTOR_CALLEE
+              TYPE_REFERENCE
+                PsiErrorElement:Type expected
+                  PsiElement(super)('super')
+            VALUE_ARGUMENT_LIST
+              PsiElement(LPAR)('(')
+              PsiElement(RPAR)(')')
+        PsiWhiteSpace(' ')
+        CLASS_BODY
           PsiElement(LBRACE)('{')
           PsiElement(RBRACE)('}')
       PsiWhiteSpace('\n')
@@ -176,45 +176,24 @@ JetFile: nestedClassAmbiguity.kt
     PsiWhiteSpace(' ')
     OBJECT_DECLARATION_NAME
       PsiElement(IDENTIFIER)('TopLevel')
-  PsiWhiteSpace(' ')
-  MODIFIER_LIST
-    ANNOTATION_ENTRY
-      CONSTRUCTOR_CALLEE
-        TYPE_REFERENCE
-          USER_TYPE
-            REFERENCE_EXPRESSION
-              PsiElement(IDENTIFIER)('constructor')
-      VALUE_ARGUMENT_LIST
-        PsiElement(LPAR)('(')
-        VALUE_ARGUMENT
-          PsiErrorElement:Expecting an expression
-            <empty list>
-        PsiErrorElement:Expecting ')'
-          PsiElement(val)('val')
     PsiWhiteSpace(' ')
-    ANNOTATION_ENTRY
-      CONSTRUCTOR_CALLEE
-        TYPE_REFERENCE
-          USER_TYPE
-            REFERENCE_EXPRESSION
-              PsiElement(IDENTIFIER)('x')
-  PsiErrorElement:Expecting a top level declaration
-    PsiElement(COLON)(':')
-  PsiWhiteSpace(' ')
-  MODIFIER_LIST
-    ANNOTATION_ENTRY
-      CONSTRUCTOR_CALLEE
-        TYPE_REFERENCE
-          USER_TYPE
-            REFERENCE_EXPRESSION
-              PsiElement(IDENTIFIER)('Int')
-  PsiErrorElement:Expecting a top level declaration
-    PsiElement(RPAR)(')')
-  PsiWhiteSpace(' ')
-  FUN
-    PsiErrorElement:Expecting a top level declaration
-      <empty list>
-    BLOCK
+    PRIMARY_CONSTRUCTOR
+      PsiElement(constructor)('constructor')
+      VALUE_PARAMETER_LIST
+        PsiElement(LPAR)('(')
+        VALUE_PARAMETER
+          PsiElement(val)('val')
+          PsiWhiteSpace(' ')
+          PsiElement(IDENTIFIER)('x')
+          PsiElement(COLON)(':')
+          PsiWhiteSpace(' ')
+          TYPE_REFERENCE
+            USER_TYPE
+              REFERENCE_EXPRESSION
+                PsiElement(IDENTIFIER)('Int')
+        PsiElement(RPAR)(')')
+    PsiWhiteSpace(' ')
+    CLASS_BODY
       PsiElement(LBRACE)('{')
       PsiWhiteSpace('\n    ')
       FUN

grammar/src/class.grm

@@ -17,12 +17,15 @@ internal class Example<X, T : Comparable<X>>(protected val x : Foo<X, T>, y : So
 class
   : modifiers ("class" | "trait") SimpleName
       typeParameters?
-      (modifiers "constructor")? ("(" functionParameter{","} ")")?
+      primaryConstructor?
       (":" annotations delegationSpecifier{","})?
       typeConstraints
       (classBody? | enumClassBody)
   ;
 
+primaryConstructor
+  : (modifiers "constructor")? ("(" functionParameter{","} ")")
+  ;
 
 classBody
   : ("{" members "}")?

grammar/src/class_members.grm

@@ -111,7 +111,7 @@ parameter
   ;
 
 object
-  : "object" SimpleName (":" delegationSpecifier{","})? classBody? // Class body can be optional: this is a declaration
+  : "object" SimpleName primaryConstructor? (":" delegationSpecifier{","})? classBody? // Class body can be optional: this is a declaration
 
 secondaryConstructor
   : modifiers "constructor" valueParameters (":" constructorDelegationCall)? block