Invalid C# code being generated

[Ozzah]

I'm trying to use ANTLR4.9 to build the ANTLR4 lexer/parser grammar from the antlr/grammars-v4 repo. ANTLR does generate the C# files without warnings or errors, however there is an invalid

const int
;

in the generated LexBasic.cs file.

In this example, I'm using antlr-4.9-complete.jar (SHA-1: 05f8b86f121c4239939b95b0eed0411dec3917e7) with the command

java -jar antlr-4.9-complete.jar -Dlanguage=CSharp -o Generated -visitor LexBasic.g4

to build just this one file. I have also tried building the whole ANTLR4 grammar set together. I've used the dotnet-based compiler using

<PropertyGroup>
  <Antlr4UseCSharpGenerator>True</Antlr4UseCSharpGenerator>
</PropertyGroup>

and I've also tried building ANTLR4.9.1 from source. Everything results in the same invalid LexBasic.cs file.

Looking at the LexBasic.g4 file, I can't see anything immediately obvious as out of place that could cause this.

[ericvergnaud]

As far as I can tell LexBasic.g4 only contains fragments so it is not a valid standalone lexer grammar. Also you are combining the official antlr with the tools from Sam Harwell. This combination is not supported. Suggest you move this topic to the google discussion group.

…

Le 11 déc. 2020 à 12:45, Ozzah ***@***.***> a écrit : I'm trying to use ANTLR4.9 to build the ANTLR4 lexer/parser grammar from the antlr/grammars-v4 <https://github.com/antlr/grammars-v4/tree/master/antlr/antlr4> repo. ANTLR does generate the C# files without warnings or errors, however there is an invalid const int ; in the generated LexBasic.cs <https://gist.github.com/Ozzah/7dadb5f782015b9f779190dcaa94d974#file-lexbasic-cs-L35-L36> file. In this example, I'm using antlr-4.9-complete.jar (SHA-1: 05f8b86f121c4239939b95b0eed0411dec3917e7) with the command java -jar antlr-4.9-complete.jar -Dlanguage=CSharp -o Generated -visitor LexBasic.g4 to build just this one file. I have also tried building the whole ANTLR4 grammar set together. I've used the dotnet-based compiler using <PropertyGroup> <Antlr4UseCSharpGenerator>True</Antlr4UseCSharpGenerator> </PropertyGroup> and I've also tried building ANTLR4.9.1 from source. Everything results in the same invalid LexBasic.cs file. Looking at the LexBasic.g4 <https://github.com/antlr/grammars-v4/blob/master/antlr/antlr4/LexBasic.g4> file, I can't see anything immediately obvious as out of place that could cause this. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#3000>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAZNQJGDJGOA4PIL3CPH3Z3SUGPWRANCNFSM4UWBI4WA>.

[KvanTTT]

It's the bug because ANTLR should throw clear error messages instead of invalid code generating.

[Ozzah]

@ericvergnaud ok, well if I go

java -jar antlr-4.9-complete.jar -Dlanguage=CSharp -o Generated -visitor LexBasic.g4 ANTLRv4Lexer.g4 ANTLRv4Parser.g4

then I get the same syntax error in LexBasic.cs, and there is no combination with Sam Harwell's tool.

[KvanTTT]

Consider the following grammar:

lexer grammar Lexer;

ANTLR produces the following error:

Lexer.g4::: grammar Lexer has no rules

But If we are trying to generate lexer for the following code:

lexer grammar Lexer;
fragment FRAGMENT: 'FRAGMENT';

ANTLR does not show any error and produces invalid code at least for C# runtime.

Obviously, it's a bug.