[QoI] Improve cryptic error message due to accidental semicolon #352

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1. JohelEGP commented on Apr 11, 2023

   

   JohelEGP

   on Apr 11, 2023

   Last edited by JohelEGP

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   I got curious about how cppfront would handle $ in identifiers: https://godbolt.org/z/9WaejfYas.

   int x$x = 0;
   main: () = {
     :() = x$x;
   }

   The same error message, error: unexpected text at end of Cpp2 code section (at 'main'). In addition to the name of the declaration, if possible, the line's tail of the unexpected text could be printed, e.g.

   main.cpp2(2,1): error: unexpected text at end of Cpp2 code section for 'main'
   main.cpp2(3,11): error: ... at 'x;'
   
2. JohelEGP commented on Apr 11, 2023

   

   JohelEGP

   on Apr 11, 2023

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   With #358 (comment) in mind, I think I know what's going on. Copying from the OP:

   g: () = { }
   f: () = {
     for v* | all next log() do :(e) = {
       foo();
       bar*;
     };
     g();
   }
   

   x.cpp2(2,9): error: ill-formed initializer (at '{')
   x.cpp2(2,1): error: unexpected text at end of Cpp2 code section (at 'f')
   x.cpp2(1,0): error: parse failed for section starting here
   

   • f doesn't match any declaration: x.cpp2(2,1): error: unexpected text at end of Cpp2 code section (at 'f').
   • The preceding error is barely closer to the offending ;: x.cpp2(2,9): error: ill-formed initializer (at '{').

   When I watched the talk that unveiled cppfront and came to try it out, more than a few times I wished the error messages were more telling. As a C++ programmer, I guessed it wouldn't want to go down the path of template error messages.

   Error messages have been improving. But in particular, those with a stack of source locations, like the one above, seemed like they could do better.

   Now, I think it should be possible to improve the status-quo. The parser could keep a record of the furthest it got.
   For the OP, I think it should generally be possible to additionally diagnose something like this:

   x.cpp2(6,4): error: unrecognized statement (at ';')
   x.cpp2(3,3): note: previous statement (at 'for').
   
3. filipsajdak commented on Apr 11, 2023

   

   filipsajdak

   on Apr 11, 2023

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   @JohelEGP I have made some improvements in diagnostics regarding semicolons. I am running tests - it there will be no impact I will push it.
4. JohelEGP commented on Apr 12, 2023

   

   JohelEGP

   on Apr 12, 2023

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   Thank you.

   The suggestion at #352 (comment) should work for more than semicolons. For example, #352 (comment) is not about the semicolon. The error message of #358 (comment) already does point to the offending token.
5. filipsajdak commented on Apr 12, 2023

   

   filipsajdak

   on Apr 12, 2023

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   I have pushed the PR: #362
6. filipsajdak commented on Apr 12, 2023

   

   filipsajdak

   on Apr 12, 2023

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   After my PR the following code:

   int x$x = 0;
   main: () = {
     :() = x$x;
   }

   produces:

   bug_352_error_message_semicolon.cpp2...
   bug_352_error_message_semicolon.cpp2(3,11): error: bad statement! (at 'x')
   

   👍React with 👍1Reacted by Johel Ernesto Guerrero Peña
7. hsutter

   closed this as completedin #362on Apr 20, 2023
8. hsutter

   added a commit that references this issue on Apr 20, 2023

   Add diagnostics for bad semicolons errors, closes #352 (#362)

   ...

   This issue will close once commit d4c001d is merged into the 'main' branch.

   d4c001d
9. zaucy

   added a commit that references this issue on Dec 5, 2023

   Add diagnostics for bad semicolons errors, closes hsutter#352 (hsutte…

   ...

   This issue will close once commit dfc10d9 is merged into the 'main' branch.

   dfc10d9