(parser) Support underscores in integer literals

[perlun]

This is really "syntactic sugar" at its finest. No sensible person could claim that this is a required language feature, but it sure is nice to have stuff like this when you need it (perhaps especially when working with many integer literals).

(Btw, the PR probably supports underscore in floating-point literals as well, I haven't tried. 😁)

[perlun]

(Btw, the PR probably supports underscore in floating-point literals as well, I haven't tried. grin)

Interestingly enough, no - it fails (just like before?).

Perlang Interactive REPL Console (0.1.0-dev.179, built from git commit 90bd9da)
> 123.45
123.45
> 123.45_67
[line 1] Error at '_67': Expect ';' after expression.

This one is even worse. Will check with the commit right before to see if it's the same there or if this is a regression introduced by this PR.

> 123_45.67
Unhandled exception: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.FormatException: Input string was not in a correct format.
   at System.Number.ThrowOverflowOrFormatException(ParsingStatus status, TypeCode type)
   at System.Double.Parse(String s)
   at Perlang.Parser.Scanner.Number() in /home/per/git/perlang/src/Perlang.Parser/Scanner.cs:line 356
   at Perlang.Parser.Scanner.ScanToken() in /home/per/git/perlang/src/Perlang.Parser/Scanner.cs:line 273
   at Perlang.Parser.Scanner.ScanTokens() in /home/per/git/perlang/src/Perlang.Parser/Scanner.cs:line 152
   at Perlang.Interpreter.PerlangInterpreter.ScanAndParse(String source, ScanErrorHandler scanErrorHandler, ParseErrorHandler parseErrorHandler) in /home/per/git/perlang/src/Perlang.Interpreter/PerlangInterpreter.cs:line 413
   at Perlang.Interpreter.PerlangInterpreter.Eval(String source, ScanErrorHandler scanErrorHandler, ParseErrorHandler parseErrorHandler, NameResolutionErrorHandler nameResolutionErrorHandler, ValidationErrorHandler typeValidationErrorHandler, ValidationErrorHandler immutabilityValidationErrorHandler, CompilerWarningHandler compilerWarningHandler) in /home/per/git/perlang/src/Perlang.Interpreter/PerlangInterpreter.cs:line 175
   at Perlang.ConsoleApp.Program.Run(String source, CompilerWarningHandler compilerWarningHandler) in /home/per/git/perlang/src/Perlang.ConsoleApp/Program.cs:line 352
   at Perlang.ConsoleApp.Program.RunPrompt() in /home/per/git/perlang/src/Perlang.ConsoleApp/Program.cs:line 346
   at Perlang.ConsoleApp.Program.<>c__DisplayClass9_0.<MainWithCustomConsole>b__3(ParseResult parseResult, IConsole console) in /home/per/git/perlang/src/Perlang.ConsoleApp/Program.cs:line 180
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at System.Delegate.DynamicInvoke(Object[] args)
   at System.CommandLine.Invocation.ModelBindingCommandHandler.InvokeAsync(InvocationContext context)
   at System.CommandLine.Invocation.InvocationPipeline.<>c__DisplayClass4_0.<<BuildInvocationChain>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass23_0.<<UseParseErrorReporting>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass16_0.<<UseHelp>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass25_0.<<UseTypoCorrections>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c.<<UseSuggestDirective>b__24_0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass22_0.<<UseParseDirective>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass11_0.<<UseDebugDirective>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c.<<RegisterWithDotnetSuggest>b__10_0>d.MoveNext()
--- End of stack trace from previous location ---
   at System.CommandLine.Builder.CommandLineBuilderExtensions.<>c__DisplayClass14_0.<<UseExceptionHandler>b__0>d.MoveNext()

[perlun]

This one is even worse. Will check with the commit right before to see if it's the same there or if this is a regression introduced by this PR.

Confirmed - it worked correctly (no System.FormatException) in 80c0bf5:

Perlang Interactive REPL Console (0.1.0-dev.177, built from git commit 80c0bf5)
> 123.45_67
[line 1] Error at '_67': Expect ';' after expression.
> 123_45.67
[line 1] Error at '_45': Expect ';' after expression.

I'll see if I can at least get rid of the exception. In the best of worlds, we should probably support underscores in floating-point literals as well.

[perlun]

I'll see if I can at least get rid of the exception. In the best of worlds, we should probably support underscores in floating-point literals as well.

Fixed in #222.