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compiler crashes when using erroneous generic routine symbol as call argument #1384

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zerbina opened this issue Jul 15, 2024 · 0 comments · Fixed by #1443
Closed

compiler crashes when using erroneous generic routine symbol as call argument #1384

zerbina opened this issue Jul 15, 2024 · 0 comments · Fixed by #1443
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bug Something isn't working compiler/sem Related to semantic-analysis system of the compiler

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@zerbina
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zerbina commented Jul 15, 2024 •
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Example

proc generic[T](x: T) =
  missing # provoke the generic pre-pass to fail (via a symbol lookup error) 

proc f(p: proc(x: int)) =
  discard

f(generic) # <- instantiation is attempted even though the symbol is erroneous

Actual Output

Error: unhandled exception: field 'sons' is not accessible for type 'TNode' using 'kind = nkError' [FieldDefect]

Expected Output

Error: undeclared identifier: 'missing'

Possible Solution

Analyzing the expression goes through semExpr, but not semSym (which would have wrapped the symbol usage in an error), due to the symbol being a skProc.

If the symChoice call part of the nkIdent handling of semExpr results in a single symbol, the symbol can be checked (and wrapped in an error) early. For the case where a symbol-choice is returned, the error wrapping can only happen where the choice is ultimately resolved.
@zerbina zerbina added bug Something isn't working compiler/sem Related to semantic-analysis system of the compiler labels Jul 15, 2024
@zerbina zerbina mentioned this issue Sep 2, 2024
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github-merge-queue bot pushed a commit that referenced this issue Sep 3, 2024
@zerbina
fix(sem): crash with procedure with error used as argument (#1443)
73b9136 
## Summary

Fix a compiler crash when passing the name of a procedure with an error
as an argument to another routine.

## Details

Overloadable and overloaded procedure symbols forewent the `nkError`
wrapping done by `semSym`, thus not preventing instantiation or later
inspection by `sempass2`, crashing the compiler with an `IndexDefect`
on attempting to access the symbol's AST.

Non-overloaded procedure symbols can be passed to `semSym` directly,
which takes care of the wrapping. To handle overloaded symbols,
`sigmatch.paramTypesMatch` passes the picked symbol to `semExpr` first,
which subsequently calls `semSym`, also marking the symbols as used.

The problem with using `semExpr` in `paramTypesMatch` is that the
returned `nkError` currently dismisses the overload, resulting in an
unnecessary "type mismatch" compiler error (with `nimsuggest`, `check`,
etc.).

Fixes #1384.
Fixes #1442.
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fix(sem): crash with procedure with error used as argument zerbina/nimskull
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