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Go target: missing constructor call to the superclass of the generated parser or lexer #4625

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RobEin opened this issue May 22, 2024 · 2 comments

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@RobEin
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RobEin commented May 22, 2024

There is currently no constructor support for superclasses from the generated lexer/parser classes.
Without this, the initial values of a superclass instance can only be set in individually way.
Here is a short example for a lexer implementation:

my PythonLexer.g4:

lexer grammar PythonLexer;
options { superClass=PythonLexerBase; }
...

my PythonLexerBase superclass:

...

type PythonLexerBase struct {
    *antlr.BaseLexer
    ...
}

// go constructor for the superclass
// unfortunately this function is not called from the generated lexer
func NewPythonLexerBase(input antlr.CharStream) *PythonLexerBase {
    plb := new(PythonLexerBase)
    plb.BaseLexer = antlr.NewBaseLexer(input)
    ...
    return plb
}

...

current generated lexer:

...

type PythonLexer struct {
    PythonLexerBase
    ...
}

...

func NewPythonLexer(input antlr.CharStream) *PythonLexer {
    ...
    l := new(PythonLexer)
    l.BaseLexer = antlr.NewBaseLexer(input) // **** there is no constructor call for the superclass
    ...
    return l
}

...

suggested generated lexer:

...

type PythonLexer struct {
    *PythonLexerBase // **** by pointer
    ...
}

...

func NewPythonLexer(input antlr.CharStream) *PythonLexer {
    ...
    l := new(PythonLexer)
    l.PythonLexerBase = NewPythonLexerBase(input) // **** constructor call for the superclass
    ...
    return l
}

...

I think this suggestion follows the practices of the Go language and those common in other ANTLR target languages.
The generated parser class should be created in the same way.

similar issue: #3446

@RobEin RobEin changed the title Missing constructor call to the superclass of the generated parser or lexer Go target: missing constructor call to the superclass of the generated parser or lexer May 23, 2024
@RobEin
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RobEin commented May 23, 2024

I submitted a PR to fix it.

@jimidle
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jimidle commented May 24, 2024 via email

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