With a particular syntax and a wrong input, I get errors and AST’s that are completely wrong and could never be the result of parsing the input.

This syntax:

context-free start-symbols
    Start

context-free syntax
    Start                               = ModuleDef
    
    ModuleDef.ModuleDef                 = <<Definition*> <Section*>>
    Definition.Imports                  = <imports <MODULEID>>
    Section.Section                     = <section <SECTIONID> <Definition*>>

    Definition                          = TemplateDefinition
    TemplateElement                     = TemplateDefinition
    
    TemplateDefinition.TemplateDefine   = <template <ID> { <TemplateDefinition*> }>
    TemplateElement.SelectFromList      = <select(<Exp> from <Exp>) { <TemplateElement*> }>
    
    Exp                                 = [[ID]]

lexical syntax
    ID                                  = [a-zA-Z][a-zA-Z0-9\_]*
    MODULEID                            = {EXTENDEDID "/"}+
    EXTENDEDID                          = [a-zA-Z0-9\_\.\-]+
    SECTIONID                           = ~[\n\r]*  
    LAYOUT                              = [\ \t\n\r]
    EOF                                 =

lexical restrictions
    ID                                  -/- [a-zA-Z0-9\_]
    MODULEID                            -/- [a-zA-Z0-9\_\.\-\/]
    EOF                                 -/- ~[]
    
context-free restrictions
    SECTIONID                           -/- ~[\n\r]
    LAYOUT?                             -/- [\ \t\n\r]

And this input:

template X
{
    select (x from x)
    {
        
    }
}

results in these errors:

Syntax error, expected: 'imports'
Syntax error, expected: 'imports'
Syntax error, expected: 'imports'
Syntax error, expected: 'section'
Syntax error, expected: 'section'
Syntax error, expected: 'section'
Syntax error, not expected here: '}'

and this AST:

ModuleDef(
  [TemplateDefine("X", []), Imports("select"), Imports("x"), Imports("from")]
, [Section(")", []), Section("{", []), Section("}", [])]
)

That AST could never be the result of that particular input. For example, the Section() constructor should only be in the AST when the section keyword is present in the input, which it is not. Same for Imports() and the imports keyword.

---

However, when I change Section.Section from this:

Section.Section                     = <section <SECTIONID> <Definition*>>

to this:

Section.Section                     = <section <ID> <Definition*>>

then parsing behaves normally again, resulting in this error:

Syntax error, not expected here: select

and this AST, as expected:

ModuleDef([TemplateDefine("X", [])], [])

---

This is not an issue with SDF3. I have attached a small project (with SDF2 syntax) that demonstrates the issue. (See examples\test.tes.)

Submitted by D. Pelsmaeker on 22 July 2014 at 11:58