Templates: Crash with gensym'ed proc & method call

[metagn]

Example

proc bar(x: int): int = 10
template foo =
  proc bar(x: int): int {.gensym.} = x + 2
  echo bar(3)
block:
  foo()

proc bar(x: int): int = 10
template foo =
  proc bar(x: int): int {.gensym.} = x + 2
  echo 3.bar
block:
  foo()

Current Output

5

compiler\nim.nim(143) nim
compiler\nim.nim(98) handleCmdLine
compiler\main.nim(284) mainCommand
compiler\main.nim(254) compileToBackend
compiler\main.nim(110) commandCompileToC
compiler\modules.nim(181) compileProject
compiler\modules.nim(101) compileModule
compiler\passes.nim(184) processModule
compiler\passes.nim(76) processTopLevelStmt
compiler\sem.nim(653) myProcess
compiler\sem.nim(621) semStmtAndGenerateGenerics
compiler\semstmts.nim(2429) semStmt
compiler\semexprs.nim(1066) semExprNoType
compiler\semexprs.nim(3026) semExpr
compiler\semstmts.nim(2371) semStmtList
compiler\semexprs.nim(3025) semExpr
compiler\semexprs.nim(2602) semBlock
compiler\semexprs.nim(3026) semExpr
compiler\semstmts.nim(2371) semStmtList
compiler\semexprs.nim(2908) semExpr
compiler\semexprs.nim(1048) semDirectOp
compiler\semexprs.nim(931) afterCallActions
compiler\semexprs.nim(39) semTemplateExpr
compiler\sem.nim(430) semAfterMacroCall
compiler\semstmts.nim(2429) semStmt
compiler\semexprs.nim(1066) semExprNoType
compiler\semexprs.nim(3026) semExpr
compiler\semstmts.nim(2371) semStmtList
compiler\semexprs.nim(2922) semExpr
compiler\semexprs.nim(2397) semMagic
compiler\semexprs.nim(1047) semDirectOp
compiler\semexprs.nim(878) semOverloadedCallAnalyseEffects
compiler\semcall.nim(588) semOverloadedCall
compiler\semcall.nim(371) resolveOverloads
compiler\semcall.nim(95) pickBestCandidate
compiler\sigmatch.nim(2574) matches
compiler\sigmatch.nim(2507) matchesAux
compiler\sigmatch.nim(2303) prepareOperand
compiler\semexprs.nim(54) semOperand
compiler\semexprs.nim(2876) semExpr
compiler\semexprs.nim(1491) semFieldAccess
compiler\semexprs.nim(1407) builtinFieldAccess
compiler\lookups.nim(55) considerQuotedIdent
lib\system\fatal.nim(53) sysFatal
Error: unhandled exception: index out of bounds, the container is empty [IndexDefect]

Expected Output

5

10?

Possible Solution

Change s to a in this line:

Nim/compiler/semtempl.nim

Line 81 in fb5fbf1

if a.kind != skModule and (not isField or sfGenSym notin s.flags):

This makes the crashing code output 10. Did not test for other consequences.

Additional Information

• Exists since 1.0 at the latest
• With inject: Templates: Method call prefers injected proc to outside, normal call doesn't #20000

$ nim -v
Nim Compiler Version 1.7.1 [Windows: amd64]
Compiled at 2022-07-11
Copyright (c) 2006-2022 by Andreas Rumpf

git hash: 8bfc396a4dfa722239818f399a119452a53fe07f