indexing over a statically declared string with a statically declared int raises `FieldDefect`.

[Luyten-Orion]

Specification

When using a constant int that is higher than the length of a constant string (haven't tested arrays as a whole), the compiler crashes instead of giving a meaningful error message.

Example

discard "a"[1]

Actual Output

(Debug compiler)

nim.nim                  nim
nim.nim                  handleCmdLine
main.nim                 mainCommand
main.nim                 compileToBackend
main.nim                 commandCompileToC
modules.nim              compileProject
modules.nim              compileModule
passes.nim               processModule
passes.nim               processTopLevelStmt
sem.nim                  myProcess
sem.nim                  semStmtAndGenerateGenerics nkStmtList 383904 /var/home/chronos/test/main.nim(1, 0)
sempass2.nim             trackStmt
sempass2.nim             track
msgs.nim                 handleReport
cli_reporter.nim         legacyReportBridge
cli_reporter.nim         astDiagToLegacyReport
ast_types.nim            len
fatal.nim                sysFatal
Error: unhandled exception: field 'sons' is not accessible for type 'TNode' using 'kind = nkStrLit' [FieldDefect]

Expected Output

Either an index defect or an error at compile time.

Error: unhandled exception: index 1 not in 0 .. 0 [IndexDefect]

Possible Solution

Additional Information

References

[zerbina]

Thanks for reporting the issue.

The problem is with the TAstDiag -> SemReport translation not taking into account that the static container may be a string constant, always trying to query the container's length with len (which is only available for nodes with children).

The translation needs to special case string constants when computing the upper index bound.