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Could the error message when passing an empty char be better? #10196

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rbjorklin opened this issue Feb 4, 2021 · 3 comments · Fixed by #10197
Closed

Could the error message when passing an empty char be better? #10196

rbjorklin opened this issue Feb 4, 2021 · 3 comments · Fixed by #10197
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@rbjorklin
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I tripped myself with this and my eyes didn't spot the missing space between the the single quotes. Unfortunately the compiler was only moderately helpful too. Could this error message be clarified?
empty-char
gasche added a commit to gasche/ocaml that referenced this issue Feb 4, 2021
@gasche
Display a clear error on empty character literals ''
2ceffce 
Before this would get correctly lexed into QUOTE QUOTE and then fail
in the parser with a generic "Syntax error" message. (Even if we had
better error messages in the parser, here the parser-level error would
not be very illuminating as ' is never the start of a valid expression
or structure item).

Fixes ocaml#10196.
gasche added a commit to gasche/ocaml that referenced this issue Feb 4, 2021
@gasche
Display a clear error on empty character literals ''
653f70f 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: The empty character literal '' is invalid. We expect a character
>        between single quotes (possibly a space ' ') or a single quote for
>        type variables 'a.

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
@gasche gasche mentioned this issue Feb 4, 2021
Merged
@gasche
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gasche commented Feb 4, 2021

Thanks for the report. I propose a fix in #10197.

gasche added a commit to gasche/ocaml that referenced this issue Feb 4, 2021
@gasche
Display a clear error on empty character literals ''
257ca3d 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal; did you mean ' ' or a type variable 'a ?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
gasche added a commit to gasche/ocaml that referenced this issue Feb 4, 2021
@gasche
Display a clear error on empty character literals ''
0e15dc4 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
> Hint: Did you mean ' ' or a type variable 'a?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
gasche added a commit to gasche/ocaml that referenced this issue Feb 4, 2021
@gasche
Display a clear error on empty character literals ''
908c5f2 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
> Hint: Did you mean ' ' or a type variable 'a?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
gasche added a commit to gasche/ocaml that referenced this issue Feb 4, 2021
@gasche
Display a clear error on empty character literals ''
2b7916a 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
> Hint: Did you mean ' ' or a type variable 'a?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
gasche added a commit to gasche/ocaml that referenced this issue Feb 5, 2021
@gasche
Display a clear error on empty character literals ''
49cd6c4 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
>   Hint: Did you mean a space character literal ' ' or a type variable 'a?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
gasche added a commit to gasche/ocaml that referenced this issue Feb 5, 2021
@gasche
Display a clear error on empty character literals ''
1e712d7 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
>   Hint: Did you mean ' ' (a space character literal) or 'a (a type variable)?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
gasche added a commit to gasche/ocaml that referenced this issue Feb 5, 2021
@gasche
Display a clear error on empty character literals ''
966d10c 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
>   Hint: Did you mean ' ' or a type variable 'a?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
@gasche
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gasche commented Feb 5, 2021 •
edited

The fix was merged, with the following error message:

Error: Illegal empty character literal ''
  Hint: Did you mean ' ' or a type variable 'a ?

@rbjorklin
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Thank you!

garrigue pushed a commit to garrigue/ocaml that referenced this issue Mar 3, 2021
@gasche @garrigue
Display a clear error on empty character literals ''
915e31d 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
>   Hint: Did you mean ' ' or a type variable 'a?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
smuenzel pushed a commit to smuenzel/ocaml that referenced this issue Mar 30, 2021
@gasche @smuenzel
Display a clear error on empty character literals ''
39b68f4 
Before:
> # '';;
> Error: Syntax error

After:
> # '';;
> Error: Illegal empty character literal ''
>   Hint: Did you mean ' ' or a type variable 'a?

Before, this input would get correctly lexed into QUOTE QUOTE and then
fail in the parser with a generic "Syntax error" message. (Even if we
had better error messages in the parser, here the parser-level error
would not be very illuminating as ' is never the start of a valid
expression or structure item).

Fixes ocaml#10196.
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Display a clear error on empty character literals '' gasche/ocaml
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@gasche @rbjorklin