Улучшена обработка ошибок, восстановление

Author: aNNiMON

src/com/annimon/ownlang/Main.java

@@ -70,10 +70,15 @@ private static void run(String input, boolean showTokens, boolean showAst) {
             }
         }
 
-        final Statement program = new Parser(tokens).parse();
+        final Parser parser = new Parser(tokens);
+        final Statement program = parser.parse();
         if (showAst) {
             System.out.println(program.toString());
         }
+        if (parser.getParseErrors().hasErrors()) {
+            System.out.println(parser.getParseErrors());
+            return;
+        }
         program.accept(new FunctionAdder());
 //        program.accept(new VariablePrinter());
         program.accept(new AssignValidator());

src/com/annimon/ownlang/parser/ParseError.java

@@ -0,0 +1,25 @@
+package com.annimon.ownlang.parser;
+
+public final class ParseError {
+
+    private final int line;
+    private final Exception exception;
+
+    public ParseError(int line, Exception exception) {
+        this.line = line;
+        this.exception = exception;
+    }
+
+    public int getLine() {
+        return line;
+    }
+
+    public Exception getException() {
+        return exception;
+    }
+
+    @Override
+    public String toString() {
+        return "ParseError on line " + line + ": " + exception.getMessage();
+    }
+}

src/com/annimon/ownlang/parser/ParseErrors.java

@@ -0,0 +1,40 @@
+package com.annimon.ownlang.parser;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+public final class ParseErrors implements Iterable<ParseError> {
+
+    private final List<ParseError> errors;
+
+    public ParseErrors() {
+        errors = new ArrayList<>();
+    }
+    
+    public void clear() {
+        errors.clear();
+    }
+    
+    public void add(Exception ex, int line) {
+        errors.add(new ParseError(line, ex));
+    }
+    
+    public boolean hasErrors() {
+        return !errors.isEmpty();
+    }
+
+    @Override
+    public Iterator<ParseError> iterator() {
+        return errors.iterator();
+    }
+
+    @Override
+    public String toString() {
+        final StringBuilder result = new StringBuilder();
+        for (ParseError error : errors) {
+            result.append(error).append(System.lineSeparator());
+        }
+        return result.toString();
+    }
+}

src/com/annimon/ownlang/parser/Parser.java

@@ -38,22 +38,55 @@ public final class Parser {
 
     private final List<Token> tokens;
     private final int size;
+    private final ParseErrors parseErrors;
 
     private int pos;
 
     public Parser(List<Token> tokens) {
         this.tokens = tokens;
         size = tokens.size();
+        parseErrors = new ParseErrors();
+    }
+    
+    public ParseErrors getParseErrors() {
+        return parseErrors;
     }
 
     public Statement parse() {
+        parseErrors.clear();
         final BlockStatement result = new BlockStatement();
         while (!match(TokenType.EOF)) {
-            result.add(statement());
+            try {
+                result.add(statement());
+            } catch (Exception ex) {
+                parseErrors.add(ex, getErrorLine());
+                recover();
+            }
         }
         return result;
     }
 
+    private int getErrorLine() {
+        if (size == 0) return 0;
+        if (pos >= size) return tokens.get(size - 1).getRow();
+        return tokens.get(pos).getRow();
+    }
+    
+    private void recover() {
+        int preRecoverPosition = pos;
+        for (int i = preRecoverPosition; i < size; i++) {
+            pos = i;
+            try {
+                statement();
+                // successfully parsed,
+                pos = i; // restore position
+                return;
+            } catch (Exception ex) {
+                // fail
+            }
+        }
+    }
+    
     private Statement block() {
         final BlockStatement block = new BlockStatement();
         consume(TokenType.LBRACE);