1099238-Lost lexical errors from literal parts of interpolated strings (changeset 1395214)

Src/Compilers/CSharp/Portable/Parser/LanguageParser_InterpolatedString.cs

@@ -189,24 +189,35 @@ private InterpolationSyntax ParseInterpolation(string text, Lexer.Interpolation
         /// <param name="kind">The token kind to be assigned to the resulting token</param>
         SyntaxToken MakeStringToken(string text, string bodyText, bool isVerbatim, SyntaxKind kind)
         {
-            var fakeString = (isVerbatim ? "@\"" : "\"") + bodyText + "\"";
+            var prefix = isVerbatim ? "@\"" : "\"";
+            var fakeString = prefix + bodyText + "\"";
             using (var tempLexer = new Lexer(Text.SourceText.From(fakeString), this.Options, allowPreprocessorDirectives: false))
             {
-                var info = default(Lexer.TokenInfo);
-                if (isVerbatim)
-                {
-                    tempLexer.ScanVerbatimStringLiteral(ref info);
-                }
-                else
+                LexerMode mode = LexerMode.Syntax;
+                SyntaxToken token = tempLexer.Lex(ref mode);
+                Debug.Assert(token.Kind == SyntaxKind.StringLiteralToken);
+                var result = SyntaxFactory.Literal(null, text, kind, token.ValueText, null);
+                if (token.ContainsDiagnostics)
                 {
-                    tempLexer.ScanStringLiteral(ref info);
+                    result = result.WithDiagnosticsGreen(MoveDiagnostics(token.GetDiagnostics(), -prefix.Length));
                 }
 
-                Debug.Assert(info.Kind == SyntaxKind.StringLiteralToken);
-                return SyntaxFactory.Literal(null, text, kind, info.StringValue, null);
+                return result;
             }
         }
 
+        DiagnosticInfo[] MoveDiagnostics(DiagnosticInfo[] infos, int offset)
+        {
+            var builder = ArrayBuilder<DiagnosticInfo>.GetInstance();
+            foreach (var info in infos)
+            {
+                var sd = info as SyntaxDiagnosticInfo;
+                builder.Add(sd?.WithOffset(sd.Offset + offset) ?? info);
+            }
+
+            return builder.ToArrayAndFree();
+        }
+
         private void ParseInterpolationStart(out SyntaxToken openBraceToken, out ExpressionSyntax expr, out SyntaxToken commaToken, out ExpressionSyntax alignmentExpression)
         {
             openBraceToken = this.EatToken(SyntaxKind.OpenBraceToken);

Src/Compilers/CSharp/Portable/Parser/Lexer_StringLiteral.cs

@@ -12,7 +12,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Syntax.InternalSyntax
 {
     internal partial class Lexer
     {
-        internal void ScanStringLiteral(ref TokenInfo info, bool allowEscapes = true)
+        private void ScanStringLiteral(ref TokenInfo info, bool allowEscapes = true)
         {
             var quoteCharacter = TextWindow.PeekChar();
             if (quoteCharacter == '\'' || quoteCharacter == '"')
@@ -151,7 +151,7 @@ private char ScanEscapeSequence(out char surrogateCharacter)
             return ch;
         }
 
-        internal void ScanVerbatimStringLiteral(ref TokenInfo info, bool allowNewlines = true)
+        private void ScanVerbatimStringLiteral(ref TokenInfo info, bool allowNewlines = true)
         {
             this.builder.Length = 0;
 

Src/Compilers/CSharp/Test/Semantic/Semantics/InterpolationTests.cs

@@ -1018,7 +1018,10 @@ static void Main(string[] args)
             CreateCompilationWithMscorlib(text).VerifyDiagnostics(
                 // (6,40): error CS8087: A '}' character may only be escaped by doubling '}}' in an interpolated string.
                 //         var x = $"{ Math.Abs(value: 1):\}";
-                Diagnostic(ErrorCode.ERR_EscapedCurly, @"\").WithArguments("}").WithLocation(6, 40)
+                Diagnostic(ErrorCode.ERR_EscapedCurly, @"\").WithArguments("}").WithLocation(6, 40),
+                // (6,40): error CS1009: Unrecognized escape sequence
+                //         var x = $"{ Math.Abs(value: 1):\}";
+                Diagnostic(ErrorCode.ERR_IllegalEscape, @"\}").WithLocation(6, 40)
                 );
         }
 
@@ -1106,5 +1109,31 @@ public void Dynamic01()
                 );
         }
 
+        [WorkItem(1099238, "DevDiv")]
+        [Fact]
+        public void Syntax04()
+        {
+            var text =
+@"using System;
+using System.Linq.Expressions;
+ 
+class Program
+{
+    static void Main()
+    {
+        Expression<Func<string>> e = () => $""\u1{0:\u2}"";
+        Console.WriteLine(e);
+    }
+}";
+            CreateCompilationWithMscorlibAndSystemCore(text).VerifyDiagnostics(
+                // (8,46): error CS1009: Unrecognized escape sequence
+                //         Expression<Func<string>> e = () => $"\u1{0:\u2}";
+                Diagnostic(ErrorCode.ERR_IllegalEscape, @"\u1").WithLocation(8, 46),
+                // (8,52): error CS1009: Unrecognized escape sequence
+                //         Expression<Func<string>> e = () => $"\u1{0:\u2}";
+                Diagnostic(ErrorCode.ERR_IllegalEscape, @"\u2").WithLocation(8, 52)
+                );
+        }
+
     }
 }