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The ANTLR 4 grammar compiler.
/*
* [The "BSD license"]
* Copyright (c) 2012-2016 Terence Parr
* Copyright (c) 2012-2016 Sam Harwell
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
// File : A3Lexer.g
// Author : Jim Idle ([email protected])
// Copyright : Free BSD - See @header clause below
// Version : First implemented as part of ANTLR 3.2 this is the self
// hosting ANTLR 3 Lexer.
//
// Description
// -----------
// This is the definitive lexer grammar for parsing ANTLR V3.x.x grammars. All other
// gramnmars are derived from this grammar via source code control integration (perforce)
// or by the gdiff tool.
//
// This grammar and its associated grmmmars A3Parser.g and A3Walker.g exhibit the following
// traits, which are recommended for all production quality grammars:
//
// 1) They are separate grammars, not composite grammars;
// 2) They implement all supporting methods in a superclass (at least this is recommended
// for language targets that support inheritence;
// 3) All errors are pushed as far down the parsing chain as possible, which means
// that the lexer tries to defer error reporting to the parser, and the parser
// tries to defer error reporting to a semantic phase consisting of a single
// walk of the AST. The reason for this is that the error messages produced
// from later phases of the parse will generally have better context and so
// be more useful to the end user. Consider the message: "Syntax error at 'options'"
// vs: "You cannot specify two options{} sections in a single grammar file".
// 4) The lexer is 'programmed' to catch common mistakes such as unterminated literals
// and report them specifically and not just issue confusing lexer mismatch errors.
//
/** Read in an ANTLR grammar and build an AST. Try not to do
* any actions, just build the tree.
*
* The phases are:
*
* A3Lexer.g (this file)
* A3Parser.g
* A3Verify.g (derived from A3Walker.g)
* assign.types.g
* define.g
* buildnfa.g
* antlr.print.g (optional)
* codegen.g
*
* Terence Parr
* University of San Francisco
* 2005
* Jim Idle (this v3 grammar)
* Temporal Wave LLC
* 2009
*/
lexer grammar ANTLRLexer;
// ==============================================================================
// Note that while this grammar does not care about order of constructs
// that don't really matter, such as options before @header etc, it must first
// be parsed by the original v2 parser, before it replaces it. That parser does
// care about order of structures. Hence we are constrained by the v2 parser
// for at least the first bootstrap release that causes this parser to replace
// the v2 version.
// ==============================================================================
// -------
// Options
//
// V3 option directives to tell the tool what we are asking of it for this
// grammar.
//
options {
// Target language is Java, which is the default but being specific
// here as this grammar is also meant as a good example grammar for
// for users.
//
language = Java;
// The super class that this lexer should expect to inherit from, and
// which contains any and all support routines for the lexer. This is
// commented out in this baseline (definitive or normative grammar)
// - see the ANTLR tool implementation for hints on how to use the super
// class
//
//superclass = AbstractA3Lexer;
}
tokens { SEMPRED; TOKEN_REF; RULE_REF; LEXER_CHAR_SET; ARG_ACTION; }
// Include the copyright in this source and also the generated source
//
@lexer::header {
/*
[The "BSD licence"]
Copyright (c) 2005-2009 Terence Parr
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. The name of the author may not be used to endorse or promote products
derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.v4.parse;
import org.antlr.v4.tool.*;
import org.antlr.v4.runtime.misc.Interval;
}
@members {
public static final int COMMENTS_CHANNEL = 2;
public CommonTokenStream tokens; // track stream we push to; need for context info
public boolean isLexerRule = false;
public void grammarError(ErrorType etype, org.antlr.runtime.Token token, Object... args) { }
/** scan backwards from current point in this.tokens list
* looking for the start of the rule or subrule.
* Return token or null if for some reason we can't find the start.
*/
public Token getRuleOrSubruleStartToken() {
if ( tokens==null ) return null;
int i = tokens.index();
int n = tokens.size();
if ( i>=n ) i = n-1; // seems index == n as we lex
while ( i>=0 && i ' $ANTLR' SRC
| ~(NLCHARS)*
)
| // Multi-line comment, which may be a documentation comment
// if it starts /** (note that we protect against accidentaly
// recognizing a comment /**/ as a documentation comment
//
'*' (
{ input.LA(2) != '/'}?=> '*' { $type = DOC_COMMENT; }
| { true }?=> // Required to cover all alts with predicates
)
// Should we support embedded multiline comments here?
//
(
// Pick out end of multiline comment and exit the loop
// if we find it.
//
{ !(input.LA(1) == '*' && input.LA(2) == '/') }?
// Anything else other than the non-greedy match of
// the comment close sequence
//
.
)*
(
// Look for the comment terminator, but if it is accidentally
// unterminated, then we will hit EOF, which will trigger the
// epsilon alt and hence we can issue an error message relative
// to the start of the unterminated multi-line comment
//
'*/'
| // Unterminated comment!
//
{
// ErrorManager.msg(Msg.UNTERMINATED_DOC_COMMENT, startLine, offset, $pos, startLine, offset, $pos, (Object)null);
}
)
| // There was nothing that made sense following the opening '/' and so
// we issue an error regarding the malformed comment
//
{
// TODO: Insert error message relative to comment start
//
}
)
{
// We do not wish to pass the comments in to the parser. If you are
// writing a formatter then you will want to preserve the comments off
// channel, but could just skip and save token space if not.
//
$channel=COMMENTS_CHANNEL;
}
;
ARG_OR_CHARSET
options {k=1;}
: {isLexerRule}?=> LEXER_CHAR_SET {$type=LEXER_CHAR_SET;}
| {!isLexerRule}?=> ARG_ACTION
{
$type=ARG_ACTION;
// Set the token text to our gathered string minus outer [ ]
String t = $text;
t = t.substring(1,t.length()-1);
setText(t);
}
;
fragment
LEXER_CHAR_SET
: '['
( '\\' ~('\r'|'\n')
| ~('\r'|'\n'|'\\'|']')
)*
']'
;
// --------------
// Argument specs
//
// Certain argument lists, such as those specifying call parameters
// to a rule invocation, or input parameters to a rule specification
// are contained within square brackets. In the lexer we consume them
// all at once and sort them out later in the grammar analysis.
//
fragment
ARG_ACTION
: '['
(
ARG_ACTION
| ('"')=>ACTION_STRING_LITERAL
| ('\'')=>ACTION_CHAR_LITERAL
| ~('['|']')
)*
']'
;
// -------
// Actions
//
// Other than making sure to distinguish between { and } embedded
// within what we have assumed to be literals in the action code, the
// job of the lexer is merely to gather the code within the action
// (delimited by {}) and pass it to the parser as a single token.
// We know that this token will be asked for its text somewhere
// in the upcoming parse, so setting the text here to exclude
// the delimiting {} is no additional overhead.
//
ACTION
: NESTED_ACTION
( '?' {$type = SEMPRED;}
( (WSNLCHARS* '=>') => WSNLCHARS* '=>' // v3 gated sempred
{
Token t = new CommonToken(input, state.type, state.channel, state.tokenStartCharIndex, getCharIndex()-1);
t.setLine(state.tokenStartLine);
t.setText(state.text);
t.setCharPositionInLine(state.tokenStartCharPositionInLine);
grammarError(ErrorType.V3_GATED_SEMPRED, t);
}
)?
)?
;
// ----------------
// Action structure
//
// Many language targets use {} as block delimiters and so we
// must recursively match {} delimited blocks to balance the
// braces. Additionally, we must make some assumptions about
// literal string representation in the target language. We assume
// that they are delimited by ' or " and so consume these
// in their own alts so as not to inadvertantly match {}.
// This rule calls itself on matching a {
//
fragment
NESTED_ACTION
@init {
// Record the start line and offsets as if we need to report an
// unterminated block, then we want to show the start of the comment
// we think is broken, not the end, where people will have to try and work
// it out themselves.
//
int startLine = getLine();
int offset = getCharPositionInLine();
}
: // Action and other blocks start with opening {
//
'{'
(
// And now we can match one of a number of embedded
// elements within the action until we find a
// } that balances the opening {. If we do not find
// the balanced } then we will hit EOF and can issue
// an error message about the brace that we belive to
// be mismatched. This won't be foolproof but we will
// be able to at least report an error against the
// opening brace that we feel is in error and this will
// guide the user to the correction as best we can.
//
// An embedded {} block
//
NESTED_ACTION
| // What appears to be a literal
//
ACTION_CHAR_LITERAL
| // We have assumed that the target language has C/Java
// type comments.
//
COMMENT
| // What appears to be a literal
//
ACTION_STRING_LITERAL
| // What appears to be an escape sequence
//
ACTION_ESC
| // Some other single character that is not
// handled above
//
~('\\'|'"'|'\''|'/'|'{'|'}')
)*
(
// Correctly balanced closing brace
//
'}'
| // Looks like have an imblanced {} block, report
// with respect to the opening brace.
//
{
// TODO: Report imbalanced {}
System.out.println("Block starting at line " + startLine + " offset " + (offset+1) + " contains imbalanced {} or is missing a }");
}
)
;
// Keywords
// --------
// keywords used to specify ANTLR v3 grammars. Keywords may not be used as
// labels for rules or in any other context where they would be ambiguous
// with the keyword vs some other identifier
// OPTIONS, TOKENS, and CHANNELS must also consume the opening brace that captures
// their option block, as this is the easiest way to parse it separate
// to an ACTION block, despite it using the same {} delimiters.
//
OPTIONS : 'options' WSNLCHARS* '{' ;
TOKENS_SPEC : 'tokens' WSNLCHARS* '{' ;
CHANNELS : 'channels' WSNLCHARS* '{' ;
IMPORT : 'import' ;
FRAGMENT : 'fragment' ;
LEXER : 'lexer' ;
PARSER : 'parser' ;
GRAMMAR : 'grammar' ;
TREE_GRAMMAR : 'tree' WSNLCHARS* 'grammar' ;
PROTECTED : 'protected' ;
PUBLIC : 'public' ;
PRIVATE : 'private' ;
RETURNS : 'returns' ;
LOCALS : 'locals' ;
THROWS : 'throws' ;
CATCH : 'catch' ;
FINALLY : 'finally' ;
MODE : 'mode' ;
// -----------
// Punctuation
//
// Character sequences used as separators, delimters, operators, etc
//
COLON : ':'
{
// scan backwards, looking for a RULE_REF or TOKEN_REF.
// which would indicate the start of a rule definition.
// If we see a LPAREN, then it's the start of the subrule.
// this.tokens is the token string we are pushing into, so
// just loop backwards looking for a rule definition. Then
// we set isLexerRule.
Token t = getRuleOrSubruleStartToken();
if ( t!=null ) {
if ( t.getType()==RULE_REF ) isLexerRule = false;
else if ( t.getType()==TOKEN_REF ) isLexerRule = true;
// else must be subrule; don't alter context
}
}
;
COLONCOLON : '::' ;
COMMA : ',' ;
SEMI : ';' ;
LPAREN : '(' ;
RPAREN : ')' ;
RARROW : '->' ;
LT : '<' ;
GT : '>' ;
ASSIGN : '=' ;
QUESTION : '?' ;
SYNPRED : '=>'
{
Token t = new CommonToken(input, state.type, state.channel,
state.tokenStartCharIndex, getCharIndex()-1);
t.setLine(state.tokenStartLine);
t.setText(state.text);
t.setCharPositionInLine(state.tokenStartCharPositionInLine);
grammarError(ErrorType.V3_SYNPRED, t);
$channel=HIDDEN;
}
;
STAR : '*' ;
PLUS : '+' ;
PLUS_ASSIGN : '+=' ;
OR : '|' ;
DOLLAR : '$' ;
DOT : '.' ; // can be WILDCARD or DOT in qid or imported rule ref
RANGE : '..' ;
AT : '@' ;
POUND : '#' ;
NOT : '~' ;
RBRACE : '}' ;
/** Allow unicode rule/token names */
ID : a=NameStartChar NameChar*
{
if ( Grammar.isTokenName($a.text) ) $type = TOKEN_REF;
else $type = RULE_REF;
}
;
fragment
NameChar : NameStartChar
| '0'..'9'
| '_'
| '\u00B7'
| '\u0300'..'\u036F'
| '\u203F'..'\u2040'
;
fragment
NameStartChar
: 'A'..'Z' | 'a'..'z'
| '\u00C0'..'\u00D6'
| '\u00D8'..'\u00F6'
| '\u00F8'..'\u02FF'
| '\u0370'..'\u037D'
| '\u037F'..'\u1FFF'
| '\u200C'..'\u200D'
| '\u2070'..'\u218F'
| '\u2C00'..'\u2FEF'
| '\u3001'..'\uD7FF'
| '\uF900'..'\uFDCF'
| '\uFDF0'..'\uFEFE'
| '\uFF00'..'\uFFFD'
; // ignores | ['\u10000-'\uEFFFF] ;
// ----------------------------
// Literals embedded in actions
//
// Note that we have made the assumption that the language used within
// actions uses the fairly standard " and ' delimiters for literals and
// that within these literals, characters are escaped using the \ character.
// There are some languages which do not conform to this in all cases, such
// as by using /string/ and so on. We will have to deal with such cases if
// if they come up in targets.
//
// Within actions, or other structures that are not part of the ANTLR
// syntax, we may encounter literal characters. Within these, we do
// not want to inadvertantly match things like '}' and so we eat them
// specifically. While this rule is called CHAR it allows for the fact that
// some languages may use/allow ' as the string delimiter.
//
fragment
ACTION_CHAR_LITERAL
: '\'' (('\\')=>ACTION_ESC | ~'\'' )* '\''
;
// Within actions, or other structures that are not part of the ANTLR
// syntax, we may encounter literal strings. Within these, we do
// not want to inadvertantly match things like '}' and so we eat them
// specifically.
//
fragment
ACTION_STRING_LITERAL
: '"' (('\\')=>ACTION_ESC | ~'"')* '"'
;
// Within literal strings and characters that are not part of the ANTLR
// syntax, we must allow for escaped character sequences so that we do not
// inadvertantly recognize the end of a string or character when the terminating
// delimiter has been esacped.
//
fragment
ACTION_ESC
: '\\' .
;
// -------
// Integer
//
// Obviously (I hope) match an aribtrary long sequence of digits.
//
INT : ('0'..'9')+
;
// -----------
// Source spec
//
// A fragment rule for picking up information about an origrinating
// file from which the grammar we are parsing has been generated. This allows
// ANTLR to report errors against the originating file and not the generated
// file.
//
fragment
SRC : 'src' WSCHARS+ file=ACTION_STRING_LITERAL WSCHARS+ line=INT
{
// TODO: Add target specific code to change the source file name and current line number
//
}
;
// --------------
// Literal string
//
// ANTLR makes no disticintion between a single character literal and a
// multi-character string. All literals are single quote delimited and
// may contain unicode escape sequences of the form \uxxxx or \u{xxxxxx},
// where x is a valid hexadecimal number.
STRING_LITERAL
: '\'' ( ( ESC_SEQ | ~('\\'|'\''|'\r'|'\n') ) )*
( '\''
| // Unterminated string literal
{
Token t = new CommonToken(input, state.type, state.channel, state.tokenStartCharIndex, getCharIndex()-1);
t.setLine(state.tokenStartLine);
t.setText(state.text);
t.setCharPositionInLine(state.tokenStartCharPositionInLine);
grammarError(ErrorType.UNTERMINATED_STRING_LITERAL, t);
}
)
;
// A valid hex digit specification
//
fragment
HEX_DIGIT : ('0'..'9'|'a'..'f'|'A'..'F') ;
// Any kind of escaped character that we can embed within ANTLR
// literal strings.
//
fragment
ESC_SEQ
: '\\'
(
// The standard escaped character set such as tab, newline, etc...
'b'|'t'|'n'|'f'|'r'|'\''|'\\'
| // A Java style Unicode escape sequence
UNICODE_ESC
| // A Swift/Hack style Unicode escape sequence
UNICODE_EXTENDED_ESC
| // An illegal escape seqeunce
~('b'|'t'|'n'|'f'|'r'|'\''|'\\'|'u') // \x for any invalid x (make sure to match char here)
{
Token t = new CommonToken(input, state.type, state.channel, getCharIndex()-2, getCharIndex()-1);
t.setText(t.getText());
t.setLine(input.getLine());
t.setCharPositionInLine(input.getCharPositionInLine()-2);
grammarError(ErrorType.INVALID_ESCAPE_SEQUENCE, t, input.substring(getCharIndex()-2,getCharIndex()-1));
}
)
;
fragment
UNICODE_ESC
@init {
// Flag to tell us whether we have a valid number of
// hex digits in the escape sequence
//
int hCount = 0;
}
: 'u' // Leadin for unicode escape sequence
// We now require 4 hex digits. Note though
// that we accept any number of characters
// and issue an error if we do not get 4. We cannot
// use an inifinite count such as + because this
// might consume too many, so we lay out the lexical
// options and issue an error at the invalid paths.
//
(
(
HEX_DIGIT { hCount++; }
(
HEX_DIGIT { hCount++; }
(
HEX_DIGIT { hCount++; }
(
// Four valid hex digits, we are good
//
HEX_DIGIT { hCount++; }
| // Three valid digits
)
| // Two valid digits
)
| // One valid digit
)
)
| // No valid hex digits at all
)
// Now check the digit count and issue an error if we need to
//
{
if (hCount < 4) {
Interval badRange = Interval.of(getCharIndex()-2-hCount, getCharIndex());
String lastChar = input.substring(badRange.b, badRange.b);
if ( lastChar.codePointAt(0)=='\'' ) {
badRange.b--;
}
String bad = input.substring(badRange.a, badRange.b);
Token t = new CommonToken(input, state.type, state.channel, badRange.a, badRange.b);
t.setLine(input.getLine());
t.setCharPositionInLine(input.getCharPositionInLine()-hCount-2);
grammarError(ErrorType.INVALID_ESCAPE_SEQUENCE, t, bad);
}
}
;
fragment
UNICODE_EXTENDED_ESC
: 'u{' // Leadin for unicode extended escape sequence
HEX_DIGIT+ // One or more hexadecimal digits
'}' // Leadout for unicode extended escape sequence
// Now check the digit count and issue an error if we need to
{
int numDigits = getCharIndex()-state.tokenStartCharIndex-6;
if (numDigits > 6) {
Token t = new CommonToken(input, state.type, state.channel, state.tokenStartCharIndex, getCharIndex()-1);
t.setText(t.getText());
t.setLine(input.getLine());
t.setCharPositionInLine(input.getCharPositionInLine()-numDigits);
grammarError(ErrorType.INVALID_ESCAPE_SEQUENCE, t, input.substring(state.tokenStartCharIndex,getCharIndex()-1));
}
}
;
// ----------
// Whitespace
//
// Characters and character constructs that are of no import
// to the parser and are used to make the grammar easier to read
// for humans.
//
WS
: (
' '
| '\t'
| '\r'
| '\n'
| '\f'
)+
{$channel=HIDDEN;}
;
// A fragment rule for use in recognizing end of line in
// rules like COMMENT.
//
fragment
NLCHARS
: '\n' | '\r'
;
// A fragment rule for recognizing traditional whitespace
// characters within lexer rules.
//
fragment
WSCHARS
: ' ' | '\t' | '\f'
;
// A fragment rule for recognizing both traditional whitespace and
// end of line markers, when we don't care to distinguish but don't
// want any action code going on.
//
fragment
WSNLCHARS
: ' ' | '\t' | '\f' | '\n' | '\r'
;
// This rule allows ANTLR 4 to parse grammars using the UTF-8 encoding with a
// byte order mark. Since this Unicode character doesn't appear as a token
// anywhere else in the grammar, we can simply skip all instances of it without
// problem. This rule will not break usage of \uFEFF inside a LEXER_CHAR_SET or
// STRING_LITERAL.
UnicodeBOM
: '\uFEFF' {skip();}
;
// -----------------
// Illegal Character
//
// This is an illegal character trap which is always the last rule in the
// lexer specification. It matches a single character of any value and being
// the last rule in the file will match when no other rule knows what to do
// about the character. It is reported as an error but is not passed on to the
// parser. This means that the parser to deal with the grammar file anyway
// but we will not try to analyse or code generate from a file with lexical
// errors.
//
ERRCHAR
: .
{
Token t = new CommonToken(input, state.type, state.channel, state.tokenStartCharIndex, getCharIndex()-1);
t.setLine(state.tokenStartLine);
t.setText(state.text);
t.setCharPositionInLine(state.tokenStartCharPositionInLine);
String msg = getTokenErrorDisplay(t) + " came as a complete surprise to me";
grammarError(ErrorType.SYNTAX_ERROR, t, msg);
state.syntaxErrors++;
skip();
}
;
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