Report issues with strings.

src/Workspaces/CSharpTest/Json/CSharpJsonParserTests_BasicTests.cs

@@ -3790,7 +3790,9 @@ public void TestMultiLineString2()
   </CompilationUnit>
 </Tree>",
         @"",
-        @"");
+        @"<Diagnostics>
+  <Diagnostic Message=""Illegal string character"" Start=""13"" Length=""1"" />
+</Diagnostics>");
         }
 
         [Fact]

src/Workspaces/Core/Portable/Json/JsonParser.StrictSyntaxChecker.cs

@@ -224,11 +224,22 @@ private struct StrictSyntaxChecker
 
             private JsonDiagnostic? CheckString(JsonToken literalToken)
             {
-                if (literalToken.VirtualChars[0].Char == '\'')
+                var chars = literalToken.VirtualChars;
+                if (chars[0].Char == '\'')
                 {
                     return new JsonDiagnostic(
                         WorkspacesResources.Strings_must_start_with_double_quote_not_single_quote,
-                        literalToken.VirtualChars[0].Span);
+                        chars[0].Span);
+                }
+
+                for (int i = 1, n = chars.Length - 1; i < n; i++)
+                {
+                    if (chars[i].Char < ' ')
+                    {
+                        return new JsonDiagnostic(
+                            WorkspacesResources.Illegal_string_character,
+                            chars[i].Span);
+                    }
                 }
 
                 return CheckToken(literalToken);

src/Workspaces/Core/Portable/WorkspacesResources.Designer.cs

@@ -863,6 +863,15 @@ internal class WorkspacesResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Illegal string character.
+        /// </summary>
+        internal static string Illegal_string_character {
+            get {
+                return ResourceManager.GetString("Illegal_string_character", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Illegal whitespace character.
         /// </summary>

src/Workspaces/Core/Portable/WorkspacesResources.resx

@@ -751,6 +751,9 @@
   <data name="Constructors_not_allowed" xml:space="preserve">
     <value>Constructors not allowed</value>
   </data>
+  <data name="Illegal_string_character" xml:space="preserve">
+    <value>Illegal string character</value>
+  </data>
   <data name="Illegal_whitespace_character" xml:space="preserve">
     <value>Illegal whitespace character</value>
   </data>

src/Workspaces/Core/Portable/xlf/WorkspacesResources.cs.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.de.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.es.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.fr.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.it.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.ja.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.ko.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.pl.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.pt-BR.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.ru.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.tr.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.zh-Hans.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file

src/Workspaces/Core/Portable/xlf/WorkspacesResources.zh-Hant.xlf

@@ -1067,6 +1067,11 @@
         <target state="new">Properties not allowed in an array</target>
         <note />
       </trans-unit>
+      <trans-unit id="Illegal_string_character">
+        <source>Illegal string character</source>
+        <target state="new">Illegal string character</target>
+        <note />
+      </trans-unit>
     </body>
   </file>
 </xliff>
\ No newline at end of file