Revert "Reject bad string interpolations (#17074)"

include/swift/AST/DiagnosticsParse.def

@@ -1224,16 +1224,6 @@ ERROR(expected_type_after_as,none,
 ERROR(string_interpolation_extra,none,
       "extra tokens after interpolated string expression", ())
 
-// Interpolated value accidentally forms a tuple.
-ERROR(string_interpolation_single_expr,none,
-      "interpolations should be a single expression", ())
-NOTE(string_interpolation_form_tuple,none,
-      "insert parentheses to form a tuple", ())
-NOTE(string_interpolation_delete_empty,none,
-      "delete empty interpolation", ())
-ERROR(string_interpolation_keyword_argument,PointsToFirstBadToken,
-      "interpolations cannot start with a keyword argument", ())
-
 // Keypath expressions.
 ERROR(expr_keypath_expected_lparen,PointsToFirstBadToken,
       "expected '(' following '#keyPath'", ())

lib/Parse/ParseExpr.cpp

@@ -1907,50 +1907,6 @@ parseStringSegments(SmallVectorImpl<Lexer::StringSegment> &Segments,
       Status |= E;
       if (E.isNonNull()) {
         Exprs.push_back(E.get());
-
-        if (auto tuple = dyn_cast<TupleExpr>(Exprs.back())) {
-          // If parseExprList() returns a TupleExpr instead of a ParenExpr, 
-          // the interpolation must have had an argument label, or the wrong 
-          // number of elements, or both. Reject these.
-          if (tuple->getNumElements() > 1) {
-            SourceLoc StartLoc = tuple->getStartLoc();
-            SourceLoc SecondExprLoc = tuple->getElement(1)->getStartLoc();
-            SourceLoc EndLoc = tuple->getEndLoc();
-
-            diagnose(SecondExprLoc, diag::string_interpolation_single_expr);
-            diagnose(StartLoc, diag::string_interpolation_form_tuple)
-              .fixItInsert(StartLoc, "(")
-              .fixItInsertAfter(EndLoc, ")");
-
-            Exprs.back() =
-              new (Context) ParenExpr(SourceLoc(), tuple, SourceLoc(), 
-                                      /*hasTrailingClosure=*/false);
-          } else if (tuple->getNumElements() == 1 && 
-                   !tuple->getElementName(0).empty()) {
-            SourceLoc NameStart = tuple->getElementNameLoc(0);
-            SourceLoc ArgStart = tuple->getElement(0)->getStartLoc();
-
-            diagnose(NameStart, diag::string_interpolation_keyword_argument)
-              .fixItRemoveChars(NameStart, ArgStart);
-
-            Exprs.back() =
-              new (Context) ParenExpr(tuple->getLParenLoc(), tuple->getElement(0), 
-                                      tuple->getRParenLoc(), /*hasTrailingClosure=*/false);
-          } else if (tuple->getNumElements() == 0 && !Status.isError()) {
-            SourceLoc StartLoc = tuple->getStartLoc();
-            SourceLoc EndLoc = tuple->getEndLoc();
-            SourceLoc SlashLoc = StartLoc.getAdvancedLocOrInvalid(-1);
-
-            diagnose(EndLoc, diag::string_interpolation_single_expr);
-            diagnose(SlashLoc, diag::string_interpolation_delete_empty)
-            .fixItRemoveChars(SlashLoc, EndLoc.getAdvancedLocOrInvalid(1));
-
-            auto Error = new (Context) ErrorExpr(SourceRange(EndLoc, EndLoc));
-            Exprs.back() =
-            new (Context) ParenExpr(SourceLoc(), Error, SourceLoc(), 
-                                    /*hasTrailingClosure=*/false);
-          } 
-        }
 
         if (!Tok.is(tok::eof)) {
           diagnose(Tok, diag::string_interpolation_extra);

lib/Parse/Parser.cpp

@@ -902,10 +902,6 @@ ParserStatus
 Parser::parseList(tok RightK, SourceLoc LeftLoc, SourceLoc &RightLoc,
                   bool AllowSepAfterLast, Diag<> ErrorDiag, SyntaxKind Kind,
                   llvm::function_ref<ParserStatus()> callback) {
-  auto TokIsStringInterpolationEOF = [&]() -> bool {
-    return Tok.is(tok::eof) && Tok.getText() == ")" && RightK == tok::r_paren;
-  };
-
   llvm::Optional<SyntaxParsingContext> ListContext;
   ListContext.emplace(SyntaxContext, Kind);
   if (Kind == SyntaxKind::Unknown)
@@ -918,10 +914,6 @@ Parser::parseList(tok RightK, SourceLoc LeftLoc, SourceLoc &RightLoc,
     RightLoc = consumeToken(RightK);
     return makeParserSuccess();
   }
-  if (TokIsStringInterpolationEOF()) {
-    RightLoc = Tok.getLoc();
-    return makeParserSuccess();
-  }
 
   ParserStatus Status;
   while (true) {
@@ -941,7 +933,7 @@ Parser::parseList(tok RightK, SourceLoc LeftLoc, SourceLoc &RightLoc,
     // If the lexer stopped with an EOF token whose spelling is ")", then this
     // is actually the tuple that is a string literal interpolation context.
     // Just accept the ")" and build the tuple as we usually do.
-    if (TokIsStringInterpolationEOF()) {
+    if (Tok.is(tok::eof) && Tok.getText() == ")" && RightK == tok::r_paren) {
       RightLoc = Tok.getLoc();
       return Status;
     }

validation-test/compiler_crashers_2_fixed/0160-sr7958.swift → validation-test/compiler_crashers_2/0160-sr7958.swift

@@ -1,4 +1,4 @@
-// RUN: not %target-swift-frontend %s -emit-ir
+// RUN: not --crash %target-swift-frontend %s -emit-ir
 
 func foo<U>(_ x: U?) {
   _ = "\(anyLabelHere: x)"