(GRAM): untagged unions

closes #781

Author: matklad

src/main/kotlin/org/rust/lang/core/RustFileElementType.kt

@@ -5,5 +5,5 @@ import org.rust.lang.RustLanguage
 import org.rust.lang.core.stubs.RustFileStub
 
 object RustFileElementType : IStubFileElementType<RustFileStub>(RustLanguage) {
-    override fun getStubVersion(): Int = 14
+    override fun getStubVersion(): Int = 15
 }

src/main/kotlin/org/rust/lang/core/grammar/rust.bnf

@@ -283,6 +283,7 @@ private item ::= static_item
                | mod_item
                | foreign_mod_item
                | struct_item
+               | union_item
                | enum_item
                | view_item
                | macro_item
@@ -566,6 +567,17 @@ struct_item ::= attrs_and_vis STRUCT IDENTIFIER generic_params? (tuple_fields? w
   elementTypeFactory = "org.rust.lang.core.stubs.ElementFactoryKt.factory"
 }
 
+// RFC 1444
+union_item ::= attrs_and_vis "union" IDENTIFIER generic_params? where_clause? block_fields {
+  hooks = [ leftBinder = "DOC_COMMENT_BINDER" ]
+  implements = [ "org.rust.lang.core.psi.RustItemElement"
+                 "org.rust.lang.core.psi.RustPathNamedElement"
+                 "org.rust.lang.core.psi.RustGenericDeclaration" ]
+  mixin = "org.rust.lang.core.psi.impl.mixin.RustUnionItemImplMixin"
+  stubClass = "org.rust.lang.core.stubs.elements.RustUnionItemElementStub"
+  elementTypeFactory = "org.rust.lang.core.stubs.ElementFactoryKt.factory"
+}
+
 enum_item ::= attrs_and_vis ENUM IDENTIFIER generic_params? where_clause? enum_body {
   hooks = [ leftBinder = "DOC_COMMENT_BINDER" ]
   implements = [ "org.rust.lang.core.resolve.scope.RustResolveScope"

src/main/kotlin/org/rust/lang/core/psi/impl/mixin/RustUnionItemImplMixin.kt

@@ -0,0 +1,26 @@
+package org.rust.lang.core.psi.impl.mixin
+
+import com.intellij.lang.ASTNode
+import com.intellij.psi.stubs.IStubElementType
+import org.rust.ide.icons.RustIcons
+import org.rust.lang.core.psi.RustUnionItemElement
+import org.rust.lang.core.psi.iconWithVisibility
+import org.rust.lang.core.psi.impl.RustPsiImplUtil
+import org.rust.lang.core.psi.impl.RustStubbedNamedElementImpl
+import org.rust.lang.core.stubs.elements.RustUnionItemElementStub
+import org.rust.lang.core.symbols.RustPath
+import javax.swing.Icon
+
+abstract class RustUnionItemImplMixin : RustStubbedNamedElementImpl<RustUnionItemElementStub>, RustUnionItemElement {
+
+    constructor(node: ASTNode) : super(node)
+
+    constructor(stub: RustUnionItemElementStub, nodeType: IStubElementType<*, *>) : super(stub, nodeType)
+
+    override fun getIcon(flags: Int): Icon =
+        iconWithVisibility(flags, RustIcons.STRUCT)
+
+    override val isPublic: Boolean get() = RustPsiImplUtil.isPublic(this)
+
+    override val canonicalCratePath: RustPath? get() = RustPsiImplUtil.canonicalCratePath(this)
+}

src/main/kotlin/org/rust/lang/core/stubs/ElementFactory.kt

@@ -17,10 +17,9 @@ fun factory(name: String): RustStubElementType<*, *> = when (name) {
     "TRAIT_METHOD_MEMBER"   -> RustTraitMethodMemberStubElementType
     "TYPE_ITEM"             -> RustTypeItemStubElementType
     "USE_ITEM"              -> RustUseItemStubElementType
+    "UNION_ITEM"            -> RustUnionItemStubElementType
     "FOREIGN_MOD_ITEM"      -> RustForeignModItemStubElementType
     "EXTERN_CRATE_ITEM"     -> RustExternCrateItemStubElementType
 
-    else               -> {
-        throw IllegalArgumentException("Unknown element $name")
-    }
+    else ->  error("Unknown element $name")
 }

src/main/kotlin/org/rust/lang/core/stubs/elements/RustUnionItem.kt

@@ -0,0 +1,39 @@
+package org.rust.lang.core.stubs.elements
+
+
+import com.intellij.psi.stubs.*
+import org.rust.lang.core.psi.RustUnionItemElement
+import org.rust.lang.core.psi.impl.RustUnionItemElementImpl
+import org.rust.lang.core.stubs.RustNamedElementStub
+import org.rust.lang.core.stubs.RustNamedStubElementType
+import org.rust.lang.core.stubs.index.RustGotoClassIndex
+
+object RustUnionItemStubElementType : RustNamedStubElementType<RustUnionItemElementStub, RustUnionItemElement>("UNION_ITEM") {
+    override fun createStub(psi: RustUnionItemElement, parentStub: StubElement<*>?): RustUnionItemElementStub =
+        RustUnionItemElementStub(parentStub, this, psi.name, psi.isPublic)
+
+    override fun createPsi(stub: RustUnionItemElementStub): RustUnionItemElement =
+        RustUnionItemElementImpl(stub, this)
+
+    override fun deserialize(dataStream: StubInputStream, parentStub: StubElement<*>?): RustUnionItemElementStub =
+        RustUnionItemElementStub(parentStub, this, dataStream.readNameAsString(), dataStream.readBoolean())
+
+    override fun serialize(stub: RustUnionItemElementStub, dataStream: StubOutputStream) = with(dataStream) {
+        writeName(stub.name)
+        writeBoolean(stub.isPublic)
+    }
+
+    override fun indexStub(stub: RustUnionItemElementStub, sink: IndexSink) {
+        super.indexStub(stub, sink)
+        stub.name?.let { sink.occurrence(RustGotoClassIndex.KEY, it) }
+    }
+
+}
+
+
+class RustUnionItemElementStub(
+    parent: StubElement<*>?,
+    elementType: IStubElementType<*, *>,
+    name: String?,
+    isPublic: Boolean
+) : RustNamedElementStub<RustUnionItemElement>(parent, elementType, name ?: "", isPublic)

src/test/kotlin/org/rust/lang/core/parser/RustCompleteParsingTestCase.kt

@@ -36,6 +36,7 @@ class RustCompleteParsingTestCase : RustParsingTestCaseBase("complete") {
     fun testAssociatedTypes() = doTest(true)
     fun testLastBlockIsExpression() = doTest(true)
     fun testLabels() = doTest(true)
+    fun testUnion() = doTest(true)
 
     fun testIssue320() = doTest(true)
 

src/test/resources/org/rust/lang/core/parser/fixtures/complete/union.rs

@@ -0,0 +1,6 @@
+#[repr(C)]
+union U {
+    i: i32,
+    f: f32,
+}
+

src/test/resources/org/rust/lang/core/parser/fixtures/complete/union.txt

@@ -0,0 +1,39 @@
+FILE
+  RustUnionItemElementImpl(UNION_ITEM)
+    RustOuterAttrElementImpl(OUTER_ATTR)
+      PsiElement(#)('#')
+      PsiElement([)('[')
+      RustMetaItemElementImpl(META_ITEM)
+        PsiElement(<IDENTIFIER>)('repr')
+        PsiElement(()('(')
+        RustMetaItemElementImpl(META_ITEM)
+          PsiElement(<IDENTIFIER>)('C')
+        PsiElement())(')')
+      PsiElement(])(']')
+    PsiWhiteSpace('\n')
+    PsiElement(<IDENTIFIER>)('union')
+    PsiWhiteSpace(' ')
+    PsiElement(<IDENTIFIER>)('U')
+    PsiWhiteSpace(' ')
+    RustBlockFieldsElementImpl(BLOCK_FIELDS)
+      PsiElement({)('{')
+      PsiWhiteSpace('\n    ')
+      RustFieldDeclElementImpl(FIELD_DECL)
+        PsiElement(<IDENTIFIER>)('i')
+        PsiElement(:)(':')
+        PsiWhiteSpace(' ')
+        RustPathTypeElementImpl(PATH_TYPE)
+          RustPathElementImpl(PATH)
+            PsiElement(<IDENTIFIER>)('i32')
+      PsiElement(,)(',')
+      PsiWhiteSpace('\n    ')
+      RustFieldDeclElementImpl(FIELD_DECL)
+        PsiElement(<IDENTIFIER>)('f')
+        PsiElement(:)(':')
+        PsiWhiteSpace(' ')
+        RustPathTypeElementImpl(PATH_TYPE)
+          RustPathElementImpl(PATH)
+            PsiElement(<IDENTIFIER>)('f32')
+      PsiElement(,)(',')
+      PsiWhiteSpace('\n')
+      PsiElement(})('}')

src/test/resources/org/rust/lang/core/parser/fixtures/partial/fn.txt

@@ -84,7 +84,7 @@ FILE
     RustBlockElementImpl(BLOCK)
       PsiElement({)('{')
       PsiWhiteSpace('\n    ')
-      PsiErrorElement:<expr>, const, enum, extern, fn, impl, mod, static, struct, trait, type or use expected, got '+'
+      PsiErrorElement:<expr>, const, enum, extern, fn, impl, mod, static, struct, trait, type, union or use expected, got '+'
         PsiElement(+)('+')
       PsiWhiteSpace('\n')
       PsiElement(})('}')