Change p compiler to return a syntax error for lexical errors

Previously, the p compiler was silently skipping over unexpected
characters encountered during lexical analysis.  Added a
listener on the lexer to raise an error when lexical analysis
encounters an error.

Added unit tests to verify this behavior.

Author: lewisbru

Src/PCompiler/CompilerCore/Compiler.cs

@@ -106,6 +106,7 @@ private static PParser.ProgramContext Parse(ICompilerConfiguration job, FileInfo
             var fileText = File.ReadAllText(inputFile.FullName);
             var fileStream = new AntlrInputStream(fileText);
             var lexer = new PLexer(fileStream);
+            lexer.AddErrorListener(new PLexerErrorListener(inputFile, job.Handler));
             var tokens = new CommonTokenStream(lexer);
             var parser = new PParser(tokens);
             parser.RemoveErrorListeners();
@@ -133,6 +134,28 @@ private static PParser.ProgramContext Parse(ICompilerConfiguration job, FileInfo
             }
         }
 
+        /// <summary>
+        /// This error listener converts Antlr lexer errors into translation exceptions via the
+        /// active error handler  
+        /// </summary>
+        private class PLexerErrorListener : IAntlrErrorListener<int>
+        {
+            private readonly ITranslationErrorHandler handler;
+            private readonly FileInfo inputFile;
+
+            public PLexerErrorListener(FileInfo inputFile, ITranslationErrorHandler handler)
+            {
+                this.inputFile = inputFile;
+                this.handler = handler;
+            }
+
+            public void SyntaxError(IRecognizer recognizer, int offendingSymbol, int line, int charPositionInLine,
+                string msg, RecognitionException e)
+            {
+                throw handler.ParseFailure(inputFile, $"line {line}:{charPositionInLine} {msg}");
+            }
+        }
+
         /// <inheritdoc />
         /// <summary>
         ///     This error listener converts Antlr parse errors into translation exceptions via the
@@ -193,4 +216,4 @@ public static int RunWithOutput(string activeDirectory,
             return proc.ExitCode;
         }
     }
-}
+}

Tst/RegressionTests/Feature1SMLevelDecls/StaticError/LexerError1/LexerError1.p

@@ -0,0 +1 @@
+type ListUsersPayload = (_: any?);

Tst/RegressionTests/Feature1SMLevelDecls/StaticError/LexerError2/LexerError2.p

@@ -0,0 +1,2 @@
+machine Name@@?@ {
+}