[SE-0393] Enable parameter packs for generic functions.

The VariadicGenerics flag still exists and is required for generic types
with parameter packs

Author: hborla

include/swift/AST/DiagnosticsSema.def

@@ -5375,6 +5375,10 @@ ERROR(tuple_pack_element_label,none,
 ERROR(vararg_not_allowed,none,
       "variadic parameter cannot appear outside of a function parameter list",
       ())
+
+ERROR(experimental_type_with_parameter_pack,none,
+      "generic types with parameter packs are experimental",
+      ())
 ERROR(expansion_not_allowed,none,
       "pack expansion %0 can only appear in a function parameter list, "
       "tuple element, or generic argument list", (Type))

lib/Parse/ParseDecl.cpp

@@ -6459,8 +6459,7 @@ ParserResult<TypeDecl> Parser::parseDeclAssociatedType(Parser::ParseDeclOptions
   }
 
   // Reject variadic associated types with a specific error.
-  if (Context.LangOpts.hasFeature(Feature::VariadicGenerics) &&
-      Tok.isContextualKeyword("each")) {
+  if (Tok.isContextualKeyword("each")) {
     const auto EachLoc = consumeToken();
     diagnose(EachLoc, diag::associatedtype_cannot_be_variadic)
         .fixItRemoveChars(EachLoc, Tok.getLoc());
@@ -6484,8 +6483,7 @@ ParserResult<TypeDecl> Parser::parseDeclAssociatedType(Parser::ParseDeclOptions
   }
 
   // Reject (early syntax) variadic associated types with a specific error.
-  if (Context.LangOpts.hasFeature(Feature::VariadicGenerics) &&
-      startsWithEllipsis(Tok)) {
+  if (startsWithEllipsis(Tok)) {
     const auto EllipsisLoc = consumeStartingEllipsis();
     const auto EllipsisEnd = Lexer::getLocForEndOfToken(SourceMgr, EllipsisLoc);
     diagnose(EllipsisLoc, diag::associatedtype_cannot_be_variadic)

lib/Parse/ParseExpr.cpp

@@ -531,8 +531,7 @@ ParserResult<Expr> Parser::parseExprUnary(Diag<> Message, bool isExprBasic) {
   tryLexRegexLiteral(/*forUnappliedOperator*/ false);
 
   // 'repeat' as an expression prefix is a pack expansion expression.
-  if (Context.LangOpts.hasFeature(Feature::VariadicGenerics) &&
-      Tok.is(tok::kw_repeat)) {
+  if (Tok.is(tok::kw_repeat)) {
     SourceLoc repeatLoc = consumeToken();
     auto patternExpr = parseExpr(Message);
     if (patternExpr.isNull())
@@ -3024,17 +3023,10 @@ ParserResult<Expr> Parser::parseTupleOrParenExpr(tok leftTok, tok rightTok) {
                     rightLoc);
 
   // A tuple with a single, unlabeled element is just parentheses.
-  if (Context.LangOpts.hasFeature(Feature::VariadicGenerics)) {
-    if (elts.size() == 1 && !isa<PackExpansionExpr>(elts[0].E) &&
-        elts[0].LabelLoc.isInvalid()) {
-      return makeParserResult(
-          status, new (Context) ParenExpr(leftLoc, elts[0].E, rightLoc));
-    }
-  } else {
-    if (elts.size() == 1 && elts[0].Label.empty()) {
-      return makeParserResult(
-          status, new (Context) ParenExpr(leftLoc, elts[0].E, rightLoc));
-    }
+  if (elts.size() == 1 && !isa<PackExpansionExpr>(elts[0].E) &&
+      elts[0].Label.empty()) {
+    return makeParserResult(
+        status, new (Context) ParenExpr(leftLoc, elts[0].E, rightLoc));
   }
 
   SmallVector<Expr *, 8> exprs;

lib/Parse/ParseGeneric.cpp

@@ -60,8 +60,7 @@ Parser::parseGenericParametersBeforeWhere(SourceLoc LAngleLoc,
 
     // Parse the 'each' keyword for a type parameter pack 'each T'.
     SourceLoc EachLoc;
-    if (Context.LangOpts.hasFeature(Feature::VariadicGenerics) &&
-        Tok.isContextualKeyword("each")) {
+    if (Tok.isContextualKeyword("each")) {
       TokReceiver->registerTokenKindChange(Tok.getLoc(),
                                            tok::contextual_keyword);
       EachLoc = consumeToken();
@@ -78,8 +77,7 @@ Parser::parseGenericParametersBeforeWhere(SourceLoc LAngleLoc,
 
     // Parse and diagnose the unsupported ellipsis for a type parameter pack
     // 'T...'.
-    if (Context.LangOpts.hasFeature(Feature::VariadicGenerics) &&
-        startsWithEllipsis(Tok)) {
+    if (startsWithEllipsis(Tok)) {
       const auto EllipsisLoc = consumeStartingEllipsis();
       // TODO: token length hardcoded because calculation for ellipsis
       // incorrectly includes '>' if one follows (as can occur in this parse).

lib/Parse/ParseStmt.cpp

@@ -68,8 +68,7 @@ bool Parser::isStartOfStmt() {
     // is a pack expansion expression.
     // FIXME: 'repeat' followed by '{' could be a pack expansion
     // with a closure pattern.
-    return !Context.LangOpts.hasFeature(Feature::VariadicGenerics) ||
-           peekToken().is(tok::l_brace);
+    return peekToken().is(tok::l_brace);
 
   case tok::pound_line:
     // #line at the start of a line is a directive, when within, it is an expr.

lib/Sema/CSSimplify.cpp

@@ -1755,8 +1755,7 @@ static ConstraintSystem::TypeMatchResult matchCallArguments(
     // We pull these out special because variadic parameters ban lots of
     // the more interesting typing constructs called out below like
     // inout and @autoclosure.
-    if (cs.getASTContext().LangOpts.hasFeature(Feature::VariadicGenerics) &&
-        paramInfo.isVariadicGenericParameter(paramIdx)) {
+    if (paramInfo.isVariadicGenericParameter(paramIdx)) {
       // If generic parameter comes from a variadic type declaration it's
       // possible that it got specialized early and is no longer represented
       // by a pack expansion type. For example, consider expression -

lib/Sema/MiscDiagnostics.cpp

@@ -293,15 +293,14 @@ static void diagSyntacticUseRestrictions(const Expr *E, const DeclContext *DC,
         }
       }
 
-      if (!Ctx.LangOpts.hasFeature(Feature::VariadicGenerics)) {
-        // Diagnose single-element tuple expressions.
-        if (auto *tupleExpr = dyn_cast<TupleExpr>(E)) {
-          if (tupleExpr->getNumElements() == 1) {
-            Ctx.Diags.diagnose(tupleExpr->getElementNameLoc(0),
-                               diag::tuple_single_element)
-              .fixItRemoveChars(tupleExpr->getElementNameLoc(0),
-                                tupleExpr->getElement(0)->getStartLoc());
-          }
+      // Diagnose single-element tuple expressions.
+      if (auto *tupleExpr = dyn_cast<TupleExpr>(E)) {
+        if (tupleExpr->getNumElements() == 1 &&
+            !isa<PackExpansionExpr>(tupleExpr->getElement(0))) {
+          Ctx.Diags.diagnose(tupleExpr->getElementNameLoc(0),
+                             diag::tuple_single_element)
+            .fixItRemoveChars(tupleExpr->getElementNameLoc(0),
+                              tupleExpr->getElement(0)->getStartLoc());
         }
       }
 

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -473,6 +473,15 @@ static void checkGenericParams(GenericContext *ownerCtx) {
     return;
 
   for (auto gp : *genericParams) {
+    // Diagnose generic types with a parameter packs if VariadicGenerics
+    // is not enabled.
+    auto *decl = ownerCtx->getAsDecl();
+    auto &ctx = decl->getASTContext();
+    if (gp->isParameterPack() && isa<GenericTypeDecl>(decl) &&
+        !ctx.LangOpts.hasFeature(Feature::VariadicGenerics)) {
+      decl->diagnose(diag::experimental_type_with_parameter_pack);
+    }
+
     TypeChecker::checkDeclAttributes(gp);
     checkInheritanceClause(gp);
   }

test/IDE/complete_repeat.swift

@@ -52,19 +52,23 @@ func enclosingFunc1() {
 // REPEAT_4: Decl[LocalVar]/Local:               local0[#Int#];
 // REPEAT_4-NOT: LocalVar
 
-repeat {
-  let local1 = 1
-  #^REPEAT_5^#
-} while
+do {
+  repeat {
+    let local1 = 1
+    #^REPEAT_5^#
+  } while
+}
 // REPEAT_5-NOT: LocalVar
 // REPEAT_5: Decl[LocalVar]/Local:               local1[#Int#];
 // REPEAT_5-NOT: LocalVar
 
-repeat {
-  let local1 = 1
+do {
   repeat {
-    let local2 = 1
-  } while #^REPEAT_COND_1^#
+    let local1 = 1
+    repeat {
+      let local2 = 1
+    } while #^REPEAT_COND_1^#
+  }
 }
 // REPEAT_COND_1-NOT: LocalVar
 // REPEAT_COND_1: Decl[LocalVar]/Local:               local1[#Int#];

test/stmt/statements.swift

@@ -271,7 +271,7 @@ func RepeatWhileStmt1() {
 }
 
 func RepeatWhileStmt2() {
-  repeat // expected-error {{expected '{' after 'repeat'}} expected-error {{expected 'while' after body of 'repeat' statement}}
+  repeat // expected-error@+1 {{expected expression}}
 }
 
 func RepeatWhileStmt4() {