B-Lang-org/bsc

Suggest missing 'valueOf' in error message

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#276 opened on Nov 8, 2020

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 (0 comments) (0 reactions) (0 assignees)Haskell (1,108 stars) (178 forks)batch import
error-messagesgood first issue

Description

If valueOf is left out of this code:

typedef 32 DataWidth;

function Bit#(DataWidth) fn (Bit#(DataWidth) x);
  //if (valueOf(DataWidth) == 64)
  if (DataWidth == 64)
    return 8;
  else
    return 4;
endfunction

then BSC, noticing that the name DataWidth is capital, looks for a constructor by that name and doesn't find one, so it reports an error about an unbound constructor name:

Error: "Test.bsv", line 5, column 7: (T0003)
  Unbound constructor `DataWidth'

It should be easy for BSC, in this case, to look for the name in the type domain and, if it's found, add a message that this name is a type and maybe a pseudo-function like valueOf is missing.

Contributor guide

Tech stack
None
Domain
developer experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic understanding of BSC compiler structure
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Investigate where BSC handles unbound constructor errors (likely in the parser or type checker). Check if the type domain information is available at that point. Then implement a check to see if the unrecognized name is a type and suggest adding `valueOf`. Look for existing similar suggestions in the codebase.