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Extending Repleo with Static Semantic Checking using JastAddJ

Explore how to enhance Repleo with static semantic checking by leveraging JastAddJ to support additional checks for placeholders and improve error handling.

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Extending Repleo with Static Semantic Checking using JastAddJ

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  1. Extending Repleo with static semantic checking using JastAdd(J) Jos Peeters

  2. Goal • Introduction • Repleo • JastAdd(J) • Coupling Concept • Progress • Proof of Concept - Booleans • Typechecking Java • Adding placeholders / name of department

  3. Goal • Repleo • Syntax safe • Static semantics? • Goal • Extend Repleo to support static semantic checking • Create additional checks concerning placeholders • Get coffee / name of department

  4. Introduction • Repleo • JastAdd • JastAddJ • Concept / name of department

  5. Repleo / name of department

  6. Repleo – Placeholders • Substitution <% Expr %> • Iterator <% foreach Expr do %> Subtemplate <% od %> • Conditional <% if Expr then %> Subtemplate1 <% else %> Subtemplate2 <% fi %> / name of department

  7. JastAdd • Java based compiler compiler system • Designed to support analyzers, transformation tools, etc. • Main Feature: Extention of Reference Attribute Grammars / name of department

  8. JastAdd – Defining languages • EBNF format <nonterminal name> : <inherits from> ::= <production rule> abstract BinNumber; IntegNumber : BinNumber ::= IntegPart:BitList; RatNumber : BinNumber ::= IntegPart:BitList FracPart:BitList; abstract BitList; SingularBitList : BitList ::= Bit; PluralBitList : BitList ::= BitList Bit; abstract Bit; Zero : Bit ::= ; One : Bit ::= / name of department

  9. JastAdd – Aspect Weaving • Reference Attribute Grammars (RAGs) • syn • inh • eq aspect BinaryNumberValue { syn double Bit.value(); inh int Bit.scale(); … eq Zero.value() = 0 eq One.value() = java.lang.Math.pow(2.0, scale()); … } / name of department

  10. JastAdd – JastAddJ • Java compiler created with JastAdd • Semantic analysis for Java1.4 • Scanner en parser included • JFlex (LEX descendent) • Beaver (YACC descendent) • Definition/handling of production rules largely only in the parser definition / name of department

  11. JastAddJ / name of department

  12. Coupling Concept / name of department

  13. Progress • Proof of concept: Booleans • Typechecking Java • Adding placeholders / name of department

  14. Proof of Concept – Booleans "(" BoolExp ")" -> BoolExp {bracket,cons("bracket")} "not" "(" BoolExp ")" -> BoolExp {cons("not")} lhs:BoolExp "&" rhs:BoolExp -> BoolExp {left, cons("and")} lhs:BoolExp "|" rhs:BoolExp -> BoolExp {left, cons("or")} BoolCon -> BoolExp {cons("constant")} "true" -> BoolCon {cons("booltrue")} "false" -> BoolCon {cons("boolfalse")} BoolRoot ::= BoolExp; abstract BoolExp; bracket : BoolExp ::= BoolExp; not : BoolExp ::= BoolExp; and : BoolExp ::= lhs: BoolExp rhs: BoolExp; or : BoolExp ::= lhs: BoolExp rhs: BoolExp; constant : BoolExp ::= BoolCon; abstract BoolCon; booltrue : BoolCon ::=; boolfalse : BoolCon ::=; / name of department

  15. Booleans(2) aspect Booleanvalue { syn boolean BoolRoot.value(); syn boolean BoolExp.value(); syn boolean BoolCon.value(); eq BoolRoot.value() = getBoolExp().value(); eq and.value() = getlhs().value() && getrhs().value(); eq or.value() = getlhs().value() || getrhs().value(); eq not.value() = !getBoolExp().value(); eq bracket.value() = getBoolExp().value(); eq booltrue.value() = true; eq boolfalse.value() = false; } / name of department

  16. Typechecking Java • Connection • SDF definition • JastAddJ definition • JastAddJ parser • rewrite of production rules • additional instantiation of checker / name of department

  17. Java – Observations • Properties • Direct (explicit) access of typed attributes • Design decisions JastAddJ • Reduce number of tree traversals • Inability of accessing siblings / name of department

  18. Java – Implementation • It works! • Not the whole language supported (yet), but almost • “creative” solutions needed to deal with language/parser differences • Tools used • ImplodePT • AddPosInfo / name of department

  19. Adding placeholders • Partial evaluation done by Repleo • Extracting placeholder subtrees from PT • Current challenge • Catching typecheck errors/warning caused by placeholders • Additional checking requirements for conditional and iterative placeholders • Dealing with ambiguities / name of department

  20. Ambiguity example Template: public class Example { <% x %> <% y %>() {} } Two possible production rules apply: public class Example { public Example() {} } public class Example { int Something() {} } / name of department

  21. Ambiguities and JastAdd • How to introduce an ambiguous/generic node into JastAdd? • Constructors have explicitly types attributes • Typechecker has (via attributes) direct contact with its children and its parent / name of department

  22. Questions / name of department

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