[Parse] Disallow space between @ and attribute name in Swift 6 mode

Author: ahoppen

include/swift/AST/DiagnosticsParse.def

@@ -1510,6 +1510,10 @@ ERROR(type_attribute_applied_to_decl,none,
 ERROR(decl_attribute_applied_to_type,none,
       "attribute can only be applied to declarations, not types", ())
 
+
+ERROR(attr_extra_whitespace_after_at,PointsToFirstBadToken,
+      "extraneous whitespace between '@' and attribute name", ())
+
 ERROR(attr_expected_lparen,none,
 "expected '(' in '%0' %select{attribute|modifier}1", (StringRef, bool))
 

include/swift/Parse/Parser.h

@@ -1147,6 +1147,7 @@ class Parser {
 
   /// Parse a specific attribute.
   ParserStatus parseDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
+                                  SourceLoc AtEndLoc,
                                   PatternBindingInitializer *&initContext,
                                   bool isFromClangAttribute = false);
 
@@ -1256,6 +1257,7 @@ class Parser {
                                         bool justChecking);
 
   ParserStatus parseTypeAttribute(TypeOrCustomAttr &result, SourceLoc AtLoc,
+                                  SourceLoc AtEndLoc,
                                   PatternBindingInitializer *&initContext,
                                   bool justChecking = false);
 

lib/ClangImporter/ImportDecl.cpp

@@ -8055,11 +8055,14 @@ ClangImporter::Implementation::importSwiftAttrAttributes(Decl *MappedDecl) {
       parser.consumeTokenWithoutFeedingReceiver();
 
       bool hadError = false;
-      SourceLoc atLoc;
-      if (parser.consumeIf(tok::at_sign, atLoc)) {
-        hadError = parser.parseDeclAttribute(
-            MappedDecl->getAttrs(), atLoc, initContext,
-            /*isFromClangAttribute=*/true).isError();
+      if (parser.Tok.is(tok::at_sign)) {
+        SourceLoc atEndLoc = parser.Tok.getRange().getEnd();
+        SourceLoc atLoc = parser.consumeToken(tok::at_sign);
+        hadError = parser
+                       .parseDeclAttribute(MappedDecl->getAttrs(), atLoc,
+                                           atEndLoc, initContext,
+                                           /*isFromClangAttribute=*/true)
+                       .isError();
       } else {
         SourceLoc staticLoc;
         StaticSpellingKind staticSpelling;

lib/Parse/ParseDecl.cpp

@@ -4202,10 +4202,15 @@ ParserResult<CustomAttr> Parser::parseCustomAttribute(
 /// Note that various attributes (like mutating, weak, and unowned) are parsed
 /// but rejected since they have context-sensitive keywords.
 ///
-ParserStatus Parser::parseDeclAttribute(
-  DeclAttributes &Attributes, SourceLoc AtLoc,
-  PatternBindingInitializer *&initContext,
-  bool isFromClangAttribute) {
+ParserStatus Parser::parseDeclAttribute(DeclAttributes &Attributes,
+                                        SourceLoc AtLoc, SourceLoc AtEndLoc,
+                                        PatternBindingInitializer *&initContext,
+                                        bool isFromClangAttribute) {
+  if (AtEndLoc != Tok.getLoc()) {
+    diagnose(AtEndLoc, diag::attr_extra_whitespace_after_at)
+        .warnUntilSwiftVersion(6);
+  }
+
   // If this not an identifier, the attribute is malformed.
   if (Tok.isNot(tok::identifier) &&
       Tok.isNot(tok::kw_in) &&
@@ -4404,8 +4409,10 @@ ParserStatus Parser::parseDeclAttribute(
 bool Parser::canParseTypeAttribute() {
   TypeOrCustomAttr result; // ignored
   PatternBindingInitializer *initContext = nullptr;
-  return !parseTypeAttribute(result, /*atLoc=*/SourceLoc(), initContext,
-                             /*justChecking*/ true).isError();
+  return !parseTypeAttribute(result, /*atLoc=*/SourceLoc(),
+                             /*atEndLoc=*/SourceLoc(), initContext,
+                             /*justChecking*/ true)
+              .isError();
 }
 
 /// Parses the '@differentiable' type attribute argument (no argument list,
@@ -4602,9 +4609,14 @@ bool Parser::parseUUIDString(UUID &uuid, Diag<> diagnostic, bool justChecking) {
 ///   canParseTypeAttribute; don't emit any diagnostics, and there's
 ///   no need to actually record the attribute
 ParserStatus Parser::parseTypeAttribute(TypeOrCustomAttr &result,
-                                        SourceLoc AtLoc,
+                                        SourceLoc AtLoc, SourceLoc AtEndLoc,
                                         PatternBindingInitializer *&initContext,
                                         bool justChecking) {
+  if (AtEndLoc != Tok.getLoc()) {
+    diagnose(AtEndLoc, diag::attr_extra_whitespace_after_at)
+        .warnUntilSwiftVersion(6);
+  }
+
   // If this not an identifier, the attribute is malformed.
   if (Tok.isNot(tok::identifier) &&
       // These are keywords that we accept as attribute names.
@@ -5038,8 +5050,9 @@ ParserStatus Parser::parseDeclAttributeList(
   ParserStatus Status;
   while (Tok.isAny(tok::at_sign, tok::pound_if)) {
     if (Tok.is(tok::at_sign)) {
-      SourceLoc AtLoc = consumeToken();
-      Status |= parseDeclAttribute(Attributes, AtLoc, initContext);
+        SourceLoc AtEndLoc = Tok.getRange().getEnd();
+        SourceLoc AtLoc = consumeToken();
+        Status |= parseDeclAttribute(Attributes, AtLoc, AtEndLoc, initContext);
     } else {
       if (!ifConfigsAreDeclAttrs && !ifConfigContainsOnlyAttributes())
         break;
@@ -5330,8 +5343,9 @@ ParserStatus Parser::ParsedTypeAttributeList::slowParse(Parser &P) {
       return status;
 
     TypeOrCustomAttr result;
+    SourceLoc AtEndLoc = Tok.getRange().getEnd();
     SourceLoc AtLoc = P.consumeToken();
-    status |= P.parseTypeAttribute(result, AtLoc, initContext);
+    status |= P.parseTypeAttribute(result, AtLoc, AtEndLoc, initContext);
     if (status.isError())
       return status;
     if (result)

test/Parse/attribute_spacing.swift

@@ -0,0 +1,6 @@
+// RUN: %target-typecheck-verify-swift -swift-version 6
+
+@ MainActor  // expected-error {{extraneous whitespace between '@' and attribute name}}
+class Foo {
+  func foo(_ x: @ escaping () -> Int) {} // expected-error {{extraneous whitespace between '@' and attribute name}}
+}