java.g

rule engine drools-2.0-beta-18

header 
{
		package org.drools.semantics.java.parser;
}

/** Java 1.3 Recognizer.
 *
 *  This grammar is in the PUBLIC DOMAIN
 * 
 *	@author John Mitchell		[e-mail]
 *	@author Terence Parr		[e-mail]
 *	@author John Lilley			[e-mail]
 *	@author Scott Stanchfield	[e-mail]
 *	@author Markus Mohnen       [e-mail]
 *  @author Peter Williams      [e-mail]
 *  @author Allan Jacobs        [e-mail]
 *  @author Steve Messick       [e-mail]
 *
 */
class JavaRecognizer extends Parser;
options {
	k = 2;                           // two token lookahead
	exportVocab=Java;                // Call its vocabulary "Java"
	codeGenMakeSwitchThreshold = 2;  // Some optimizations
	codeGenBitsetTestThreshold = 3;
	defaultErrorHandler = false;     // Don't generate parser error handlers
	buildAST = true;
}

tokens {
	BLOCK; MODIFIERS; OBJBLOCK; SLIST; CTOR_DEF; METHOD_DEF; VARIABLE_DEF; 
	INSTANCE_INIT; STATIC_INIT; TYPE; CLASS_DEF; INTERFACE_DEF; 
	PACKAGE_DEF; ARRAY_DECLARATOR; EXTENDS_CLAUSE; IMPLEMENTS_CLAUSE;
	PARAMETERS; PARAMETER_DEF; LABELED_STAT; TYPECAST; INDEX_OP; 
	POST_INC; POST_DEC; METHOD_CALL; EXPR; ARRAY_INIT; 
	IMPORT; UNARY_MINUS; UNARY_PLUS; CASE_GROUP; ELIST; FOR_INIT; FOR_CONDITION; 
	FOR_ITERATOR; EMPTY_STAT; FINAL="final"; ABSTRACT="abstract";
	STRICTFP="strictfp"; SUPER_CTOR_CALL; CTOR_CALL;

	RULE_SET="ruleset"; RULE="rule"; WHEN="when"; THEN="then";
}
	
// Compilation Unit: In Java, this is a single file.  This is the start
//   rule for this parser
compilationUnit
	:	// A compilation unit starts with an optional package definition
		(	packageDefinition
		|	/* nothing */
		)

		// Next we have a series of zero or more import statements
		( importDefinition )*

		// Wrapping things up with any number of class or interface
		//    definitions
		( typeDefinition )*

		EOF!
	;

ruleFile
	:
		(	packageDefinition
		|	/* nothing */
		)

		( importDefinition )*

		ruleSet
	;

ruleSet
	:
		RULE_SET^ IDENT

		LCURLY!
			( rule )+
		RCURLY!
	;

rule
	:
		RULE^ IDENT 

				LPAREN! param:parameterDeclarationList RPAREN!

		LCURLY!

			( parameterDeclaration )*

			whenBlock
	
			thenBlock

		RCURLY!
	;

whenBlock
	:
		WHEN^

		LCURLY!
			(	(	consistentAssignmentExpression 
				|	inclusiveOrExpression 
				)	SEMI! 
			)+
		RCURLY!
	;

thenBlock
	:
		THEN^

		compoundStatement
	;

consistentAssignmentExpression
	:
		IDENT ASSIGN^ inclusiveOrExpression
	;

ruleCondition
	:
		inclusiveOrExpression
	;
//			consistentAssignmentExpression
//		|	inclusiveOrExpression


// Package statement: "package" followed by an identifier.
packageDefinition
	options {defaultErrorHandler = true;} // let ANTLR handle errors
	:	p:"package"^ {#p.setType(PACKAGE_DEF);} identifier SEMI!
	;


// Import statement: import followed by a package or class name
importDefinition
	options {defaultErrorHandler = true;}
	:	i:"import"^ {#i.setType(IMPORT);} identifierStar SEMI!
	;

// A type definition in a file is either a class or interface definition.
typeDefinition
	options {defaultErrorHandler = true;}
	:	m:modifiers!
		( classDefinition[#m]
		| interfaceDefinition[#m]
		)
	|	SEMI!
	;

/** A declaration is the creation of a reference or primitive-type variable
 *  Create a separate Type/Var tree for each var in the var list.
 */
declaration!
	:	m:modifiers t:typeSpec[false] v:variableDefinitions[#m,#t]
		{#declaration = #v;}
	;

// A type specification is a type name with possible brackets afterwards
//   (which would make it an array type).
typeSpec[boolean addImagNode]
	: classTypeSpec[addImagNode]
	| builtInTypeSpec[addImagNode]
	;

// A class type specification is a class type with possible brackets afterwards
//   (which would make it an array type).
classTypeSpec[boolean addImagNode]
	:	identifier (lb:LBRACK^ {#lb.setType(ARRAY_DECLARATOR);} RBRACK!)*
		{
			if ( addImagNode ) {
				#classTypeSpec = #(#[TYPE,"TYPE"], #classTypeSpec);
			}
		}
	;

// A builtin type specification is a builtin type with possible brackets
// afterwards (which would make it an array type).
builtInTypeSpec[boolean addImagNode]
	:	builtInType (lb:LBRACK^ {#lb.setType(ARRAY_DECLARATOR);} RBRACK!)*
		{
			if ( addImagNode ) {
				#builtInTypeSpec = #(#[TYPE,"TYPE"], #builtInTypeSpec);
			}
		}
	;

// A type name. which is either a (possibly qualified) class name or
//   a primitive (builtin) type
type
	:	identifier
	|	builtInType
	;

// The primitive types.
builtInType
	:	"void"
	|	"boolean"
	|	"byte"
	|	"char"
	|	"short"
	|	"int"
	|	"float"
	|	"long"
	|	"double"
	;

// A (possibly-qualified) java identifier.  We start with the first IDENT
//   and expand its name by adding dots and following IDENTS
identifier
	:	IDENT  ( DOT^ IDENT )*
	;

identifierStar
	:	IDENT
		( DOT^ IDENT )*
		( DOT^ STAR  )?
	;

// A list of zero or more modifiers.  We could have used (modifier)* in
//   place of a call to modifiers, but I thought it was a good idea to keep
//   this rule separate so they can easily be collected in a Vector if
//   someone so desires
modifiers
	:	( modifier )*
		{#modifiers = #([MODIFIERS, "MODIFIERS"], #modifiers);}
	;

// modifiers for Java classes, interfaces, class/instance vars and methods
modifier
	:	"private"
	|	"public"
	|	"protected"
	|	"static"
	|	"transient"
	|	"final"
	|	"abstract"
	|	"native"
	|	"threadsafe"
	|	"synchronized"
//	|	"const"			// reserved word, but not valid
	|	"volatile"
	|	"strictfp"
	;

// Definition of a Java class
classDefinition![AST modifiers]
	:	"class" IDENT
		// it _might_ have a superclass...
		sc:superClassClause
		// it might implement some interfaces...
		ic:implementsClause
		// now parse the body of the class
		cb:classBlock
		{#classDefinition = #(#[CLASS_DEF,"CLASS_DEF"],
							   modifiers,IDENT,sc,ic,cb);}
	;

superClassClause!
	:	( "extends" id:identifier )?
		{#superClassClause = #(#[EXTENDS_CLAUSE,"EXTENDS_CLAUSE"],id);}
	;

// Definition of a Java Interface
interfaceDefinition![AST modifiers]
	:	"interface" IDENT
		// it might extend some other interfaces
		ie:interfaceExtends
		// now parse the body of the interface (looks like a class...)
		cb:classBlock
		{#interfaceDefinition = #(#[INTERFACE_DEF,"INTERFACE_DEF"],
									modifiers,IDENT,ie,cb);}
	;


// This is the body of a class.  You can have fields and extra semicolons,
// That's about it (until you see what a field is...)
classBlock
	:	LCURLY!
			( field | SEMI! )*
		RCURLY!
		{#classBlock = #([OBJBLOCK, "OBJBLOCK"], #classBlock);}
	;

// An interface can extend several other interfaces...
interfaceExtends
	:	(
		e:"extends"!
		identifier ( COMMA! identifier )*
		)?
		{#interfaceExtends = #(#[EXTENDS_CLAUSE,"EXTENDS_CLAUSE"],
							#interfaceExtends);}
	;

// A class can implement several interfaces...
implementsClause
	:	(
			i:"implements"! identifier ( COMMA! identifier )*
		)?
		{#implementsClause = #(#[IMPLEMENTS_CLAUSE,"IMPLEMENTS_CLAUSE"],
								 #implementsClause);}
	;

// Now the various things that can be defined inside a class or interface...
// Note that not all of these are really valid in an interface (constructors,
//   for example), and if this grammar were used for a compiler there would
//   need to be some semantic checks to make sure we're doing the right thing...
field!
	:	// method, constructor, or variable declaration
		mods:modifiers
		(	h:ctorHead s:constructorBody // constructor
			{#field = #(#[CTOR_DEF,"CTOR_DEF"], mods, h, s);}

		|	cd:classDefinition[#mods]       // inner class
			{#field = #cd;}
			
		|	id:interfaceDefinition[#mods]   // inner interface
			{#field = #id;}

		|	t:typeSpec[false]  // method or variable declaration(s)
			(	IDENT  // the name of the method

				// parse the formal parameter declarations.
				LPAREN! param:parameterDeclarationList RPAREN!

				rt:declaratorBrackets[#t]

				// get the list of exceptions that this method is
				// declared to throw
				(tc:throwsClause)?

				( s2:compoundStatement | SEMI )
				{#field = #(#[METHOD_DEF,"METHOD_DEF"],
						     mods,
							 #(#[TYPE,"TYPE"],rt),
							 IDENT,
							 param,
							 tc,
							 s2);}
			|	v:variableDefinitions[#mods,#t] SEMI
//				{#field = #(#[VARIABLE_DEF,"VARIABLE_DEF"], v);}
				{#field = #v;}
			)
		)

    // "static { ... }" class initializer
	|	"static" s3:compoundStatement
		{#field = #(#[STATIC_INIT,"STATIC_INIT"], s3);}

    // "{ ... }" instance initializer
	|	s4:compoundStatement
		{#field = #(#[INSTANCE_INIT,"INSTANCE_INIT"], s4);}
	;

constructorBody
    :   lc:LCURLY^ {#lc.setType(SLIST);}
		// Predicate might be slow but only checked once per constructor def
		// not for general methods.
		(	(explicitConstructorInvocation) => explicitConstructorInvocation
		|
		)
        (statement)*
        RCURLY!
    ;

explicitConstructorInvocation
    :   (	options {
				// this/super can begin a primaryExpression too; with finite
				// lookahead ANTLR will think the 3rd alternative conflicts
				// with 1, 2.  I am shutting off warning since ANTLR resolves
				// the nondeterminism by correctly matching alts 1 or 2 when
				// it sees this( or super(
				generateAmbigWarnings=false;
			}
		:	"this"! lp1:LPAREN^ argList RPAREN! SEMI!
			{#lp1.setType(CTOR_CALL);}

	    |   "super"! lp2:LPAREN^ argList RPAREN! SEMI!
			{#lp2.setType(SUPER_CTOR_CALL);}

			// (new Outer()).super()  (create enclosing instance)
		|	primaryExpression DOT! "super"! lp3:LPAREN^ argList RPAREN! SEMI!
			{#lp3.setType(SUPER_CTOR_CALL);}
		)
    ;

variableDefinitions[AST mods, AST t]
	:	variableDeclarator[getASTFactory().dupTree(mods),
						   getASTFactory().dupTree(t)]
		(	COMMA!
			variableDeclarator[getASTFactory().dupTree(mods),
							   getASTFactory().dupTree(t)]
		)*
	;

/** Declaration of a variable.  This can be a class/instance variable,
 *   or a local variable in a method
 * It can also include possible initialization.
 */
variableDeclarator![AST mods, AST t]
	:	id:IDENT d:declaratorBrackets[t] v:varInitializer
		{#variableDeclarator = #(#[VARIABLE_DEF,"VARIABLE_DEF"], mods, #(#[TYPE,"TYPE"],d), id, v);}
	;

declaratorBrackets[AST typ]
	:	{#declaratorBrackets=typ;}
		(lb:LBRACK^ {#lb.setType(ARRAY_DECLARATOR);} RBRACK!)*
	;

varInitializer
	:	( ASSIGN^ initializer )?
	;

// This is an initializer used to set up an array.
arrayInitializer
	:	lc:LCURLY^ {#lc.setType(ARRAY_INIT);}
			(	initializer
				(
					// CONFLICT: does a COMMA after an initializer start a new
					//           initializer or start the option ',' at end?
					//           ANTLR generates proper code by matching
					//			 the comma as soon as possible.
					options {
						warnWhenFollowAmbig = false;
					}
				:
					COMMA! initializer
				)*
				(COMMA!)?
			)?
		RCURLY!
	;


// The two "things" that can initialize an array element are an expression
//   and another (nested) array initializer.
initializer
	:	expression
	|	arrayInitializer
	;

// This is the header of a method.  It includes the name and parameters
//   for the method.
//   This also watches for a list of exception classes in a "throws" clause.
ctorHead
	:	IDENT  // the name of the method

		// parse the formal parameter declarations.
		LPAREN! parameterDeclarationList RPAREN!

		// get the list of exceptions that this method is declared to throw
		(throwsClause)?
	;

// This is a list of exception classes that the method is declared to throw
throwsClause
	:	"throws"^ identifier ( COMMA! identifier )*
	;


// A list of formal parameters
parameterDeclarationList
	:	( parameterDeclaration ( COMMA! parameterDeclaration )* )?
		{#parameterDeclarationList = #(#[PARAMETERS,"PARAMETERS"],
									#parameterDeclarationList);}
	;

// A formal parameter.
parameterDeclaration!
	:	pm:parameterModifier t:typeSpec[false] id:IDENT
		pd:declaratorBrackets[#t]
		{#parameterDeclaration = #(#[PARAMETER_DEF,"PARAMETER_DEF"],
									pm, #([TYPE,"TYPE"],pd), id);}
	;

parameterModifier
	:	(f:"final")?
		{#parameterModifier = #(#[MODIFIERS,"MODIFIERS"], f);}
	;

// Compound statement.  This is used in many contexts:
//   Inside a class definition prefixed with "static":
//      it is a class initializer
//   Inside a class definition without "static":
//      it is an instance initializer
//   As the body of a method
//   As a completely indepdent braced block of code inside a method
//      it starts a new scope for variable definitions

compoundStatement
	:	lc:LCURLY^ {#lc.setType(SLIST);}
			// include the (possibly-empty) list of statements
			(statement)*
		RCURLY!
	;


statement
	// A list of statements in curly braces -- start a new scope!
	:	compoundStatement

	// declarations are ambiguous with "ID DOT" relative to expression
	// statements.  Must backtrack to be sure.  Could use a semantic
	// predicate to test symbol table to see what the type was coming
	// up, but that's pretty hard without a symbol table ;)
	|	(declaration)=> declaration SEMI!

	// An expression statement.  This could be a method call,
	// assignment statement, or any other expression evaluated for
	// side-effects.
	|	expression SEMI!

	// class definition
	|	m:modifiers! classDefinition[#m]

	// Attach a label to the front of a statement
	|	IDENT c:COLON^ {#c.setType(LABELED_STAT);} statement

	// If-else statement
	|	"if"^ LPAREN! expression RPAREN! statement
		(
			// CONFLICT: the old "dangling-else" problem...
			//           ANTLR generates proper code matching
			//			 as soon as possible.  Hush warning.
			options {
				warnWhenFollowAmbig = false;
			}
		:
			"else"! statement
		)?

	// For statement
	|	"for"^
			LPAREN!
				forInit SEMI!   // initializer
				forCond	SEMI!   // condition test
				forIter         // updater
			RPAREN!
			statement                     // statement to loop over

	// While statement
	|	"while"^ LPAREN! expression RPAREN! statement

	// do-while statement
	|	"do"^ statement "while"! LPAREN! expression RPAREN! SEMI!

	// get out of a loop (or switch)
	|	"break"^ (IDENT)? SEMI!

	// do next iteration of a loop
	|	"continue"^ (IDENT)? SEMI!

	// Return an expression
	|	"return"^ (expression)? SEMI!

	// switch/case statement
	|	"switch"^ LPAREN! expression RPAREN! LCURLY!
			( casesGroup )*
		RCURLY!

	// exception try-catch block
	|	tryBlock

	// throw an exception
	|	"throw"^ expression SEMI!

	// synchronize a statement
	|	"synchronized"^ LPAREN! expression RPAREN! compoundStatement

	// empty statement
	|	s:SEMI {#s.setType(EMPTY_STAT);}
	;


casesGroup
	:	(	// CONFLICT: to which case group do the statements bind?
			//           ANTLR generates proper code: it groups the
			//           many "case"/"default" labels together then
			//           follows them with the statements
			options {
				warnWhenFollowAmbig = false;
			}
			:
			aCase
		)+
		caseSList
		{#casesGroup = #([CASE_GROUP, "CASE_GROUP"], #casesGroup);}
	;

aCase
	:	("case"^ expression | "default") COLON!
	;

caseSList
	:	(statement)*
		{#caseSList = #(#[SLIST,"SLIST"],#caseSList);}
	;

// The initializer for a for loop
forInit
		// if it looks like a declaration, it is
	:	(	(declaration)=> declaration
		// otherwise it could be an expression list...
		|	expressionList
		)?
		{#forInit = #(#[FOR_INIT,"FOR_INIT"],#forInit);}
	;

forCond
	:	(expression)?
		{#forCond = #(#[FOR_CONDITION,"FOR_CONDITION"],#forCond);}
	;

forIter
	:	(expressionList)?
		{#forIter = #(#[FOR_ITERATOR,"FOR_ITERATOR"],#forIter);}
	;