5 files changed, 17 insertions, 13 deletions
diff --git a/lib/core/typeinfo.nim b/lib/core/typeinfo.nim
index 32fedd0c1..d6dd16b54 100644
--- a/lib/core/typeinfo.nim
+++ b/lib/core/typeinfo.nim
@@ -27,6 +27,8 @@
 include "system/inclrtl.nim"
 include "system/hti.nim"
 
+import system/indexerrors
+
 {.pop.}
 
 type
@@ -201,14 +203,14 @@ proc `[]`*(x: Any, i: int): Any =
   of tyArray:
     var bs = x.rawType.base.size
     if i >=% x.rawType.size div bs:
-      raise newException(IndexError, "index out of bounds")
+      raise newException(IndexError, formatErrorIndexBound(i, x.rawType.size div bs))
     return newAny(x.value +!! i*bs, x.rawType.base)
   of tySequence:
     var s = cast[ppointer](x.value)[]
     if s == nil: raise newException(ValueError, "sequence is nil")
     var bs = x.rawType.base.size
     if i >=% cast[PGenSeq](s).len:
-      raise newException(IndexError, "index out of bounds")
+      raise newException(IndexError, formatErrorIndexBound(i, cast[PGenSeq](s).len-1))
     return newAny(s +!! (GenericSeqSize+i*bs), x.rawType.base)
   else: assert false
 
@@ -218,7 +220,7 @@ proc `[]=`*(x: Any, i: int, y: Any) =
   of tyArray:
     var bs = x.rawType.base.size
     if i >=% x.rawType.size div bs:
-      raise newException(IndexError, "index out of bounds")
+      raise newException(IndexError, formatErrorIndexBound(i, x.rawType.size div bs))
     assert y.rawType == x.rawType.base
     genericAssign(x.value +!! i*bs, y.value, y.rawType)
   of tySequence:
@@ -226,7 +228,7 @@ proc `[]=`*(x: Any, i: int, y: Any) =
     if s == nil: raise newException(ValueError, "sequence is nil")
     var bs = x.rawType.base.size
     if i >=% cast[PGenSeq](s).len:
-      raise newException(IndexError, "index out of bounds")
+      raise newException(IndexError, formatErrorIndexBound(i, cast[PGenSeq](s).len-1))
     assert y.rawType == x.rawType.base
     genericAssign(s +!! (GenericSeqSize+i*bs), y.value, y.rawType)
   else: assert false
diff --git a/lib/pure/collections/sharedstrings.nim b/lib/pure/collections/sharedstrings.nim
index b283cd4b1..ca52ec63c 100644
--- a/lib/pure/collections/sharedstrings.nim
+++ b/lib/pure/collections/sharedstrings.nim
@@ -12,7 +12,7 @@
 type
   UncheckedCharArray = UncheckedArray[char]
 
-import system/helpers2
+import system/indexerrors
 
 type
   Buffer = ptr object
diff --git a/lib/pure/os.nim b/lib/pure/os.nim
index e88c3c6e8..0b9c8babc 100644
--- a/lib/pure/os.nim
+++ b/lib/pure/os.nim
@@ -47,7 +47,7 @@
 include "system/inclrtl"
 
 import
-  strutils, pathnorm
+  strutils, pathnorm, system/indexerrors
 
 const weirdTarget = defined(nimscript) or defined(js)
 
@@ -2551,7 +2551,7 @@ elif defined(windows):
       ownArgv = parseCmdLine($getCommandLine())
       ownParsedArgv = true
     if i < ownArgv.len and i >= 0: return TaintedString(ownArgv[i])
-    raise newException(IndexError, "invalid index")
+    raise newException(IndexError, formatErrorIndexBound(i, ownArgv.len-1))
 
 elif defined(genode):
   proc paramStr*(i: int): TaintedString =
@@ -2570,7 +2570,7 @@ elif not defined(createNimRtl) and
   proc paramStr*(i: int): TaintedString {.tags: [ReadIOEffect].} =
     # Docstring in nimdoc block.
     if i < cmdCount and i >= 0: return TaintedString($cmdLine[i])
-    raise newException(IndexError, "invalid index")
+    raise newException(IndexError, formatErrorIndexBound(i, cmdCount-1))
 
   proc paramCount*(): int {.tags: [ReadIOEffect].} =
     # Docstring in nimdoc block.
diff --git a/lib/system/indexerrors.nim b/lib/system/indexerrors.nim
index 8bd69ad71..cb1d522c9 100644
--- a/lib/system/indexerrors.nim
+++ b/lib/system/indexerrors.nim
@@ -1,7 +1,7 @@
 # imported by other modules, unlike helpers.nim which is included
 
 template formatErrorIndexBound*[T](i, a, b: T): string =
-  "index out of bounds: (a: " & $a & ") <= (i: " & $i & ") <= (b: " & $b & ") "
+  "index " & $i & " not in " & $a & " .. " & $b
 
 template formatErrorIndexBound*[T](i, n: T): string =
-  "index out of bounds: (i: " & $i & ") <= (n: " & $n & ") "
+  formatErrorIndexBound(i, 0, n)
diff --git a/lib/system/jssys.nim b/lib/system/jssys.nim
index d7718e4f4..27dd9b020 100644
--- a/lib/system/jssys.nim
+++ b/lib/system/jssys.nim
@@ -7,6 +7,8 @@
 #    distribution, for details about the copyright.
 #
 
+import system/indexerrors
+
 proc log*(s: cstring) {.importc: "console.log", varargs, nodecl.}
 
 type
@@ -157,8 +159,8 @@ proc raiseDivByZero {.exportc: "raiseDivByZero", noreturn, compilerProc.} =
 proc raiseRangeError() {.compilerproc, noreturn.} =
   raise newException(RangeError, "value out of range")
 
-proc raiseIndexError() {.compilerproc, noreturn.} =
-  raise newException(IndexError, "index out of bounds")
+proc raiseIndexError(i, a, b: int) {.compilerproc, noreturn.} =
+  raise newException(IndexError, formatErrorIndexBound(int(i), int(a), int(b)))
 
 proc raiseFieldError(f: string) {.compilerproc, noreturn.} =
   raise newException(FieldError, f & " is not accessible")
@@ -626,7 +628,7 @@ proc arrayConstr(len: int, value: JSRef, typ: PNimType): JSRef {.
 
 proc chckIndx(i, a, b: int): int {.compilerproc.} =
   if i >= a and i <= b: return i
-  else: raiseIndexError()
+  else: raiseIndexError(i, a, b)
 
 proc chckRange(i, a, b: int): int {.compilerproc.} =
   if i >= a and i <= b: return i