reserve sysFatal for Defect (nim-lang#22158)

Per manual, `panics:on` affects _only_ `Defect`:s - thus `sysFatal`
should not redirect any other exceptions.

Also, when `sysFatal` is used in `nimPanics` mode, it should use regular
exception handling pipeline to ensure exception hooks are called
consistently for all raised defects.

lib/std/syncio.nim

@@ -151,14 +151,11 @@ proc c_fprintf(f: File, frmt: cstring): cint {.
 proc c_fputc(c: char, f: File): cint {.
   importc: "fputc", header: "<stdio.h>".}
 
-template sysFatal(exc, msg) =
-  raise newException(exc, msg)
-
 proc raiseEIO(msg: string) {.noinline, noreturn.} =
-  sysFatal(IOError, msg)
+  raise newException(IOError, msg)
 
 proc raiseEOF() {.noinline, noreturn.} =
-  sysFatal(EOFError, "EOF reached")
+  raise newException(EOFError, "EOF reached")
 
 proc strerror(errnum: cint): cstring {.importc, header: "<string.h>".}
 
@@ -764,7 +761,7 @@ proc open*(filename: string,
   ##
   ## The file handle associated with the resulting `File` is not inheritable.
   if not open(result, filename, mode, bufSize):
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
 proc setFilePos*(f: File, pos: int64, relativeTo: FileSeekPos = fspSet) {.benign.} =
   ## Sets the position of the file pointer that is used for read/write
@@ -852,7 +849,7 @@ proc readFile*(filename: string): string {.tags: [ReadIOEffect], benign.} =
     finally:
       close(f)
   else:
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
 proc writeFile*(filename, content: string) {.tags: [WriteIOEffect], benign.} =
   ## Opens a file named `filename` for writing. Then writes the
@@ -865,7 +862,7 @@ proc writeFile*(filename, content: string) {.tags: [WriteIOEffect], benign.} =
     finally:
       close(f)
   else:
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
 proc writeFile*(filename: string, content: openArray[byte]) {.since: (1, 1).} =
   ## Opens a file named `filename` for writing. Then writes the
@@ -895,7 +892,7 @@ proc readLines*(filename: string, n: Natural): seq[string] =
     finally:
       close(f)
   else:
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
 template readLines*(filename: string): seq[
     string] {.deprecated: "use readLines with two arguments".} =

lib/system.nim

@@ -2832,7 +2832,7 @@ when notJSnotNims:
                     hostOS != "any"
 
   proc raiseEIO(msg: string) {.noinline, noreturn.} =
-    sysFatal(IOError, msg)
+    raise newException(IOError, msg)
 
   proc echoBinSafe(args: openArray[string]) {.compilerproc.} =
     when defined(androidNDK):

lib/system/channels_builtin.nim

@@ -394,7 +394,7 @@ proc llRecv(q: PRawChannel, res: pointer, typ: PNimType) =
   q.ready = false
   if typ != q.elemType:
     releaseSys(q.lock)
-    sysFatal(ValueError, "cannot receive message of wrong type")
+    raise newException(ValueError, "cannot receive message of wrong type")
   rawRecv(q, res, typ)
   if q.maxItems > 0 and q.count == q.maxItems - 1:
     # Parent thread is awaiting in send. Wake it up.

lib/system/fatal.nim

@@ -16,19 +16,19 @@ const
 when hostOS == "standalone":
   include "$projectpath/panicoverride"
 
-  func sysFatal(exceptn: typedesc, message: string) {.inline.} =
+  func sysFatal(exceptn: typedesc[Defect], message: string) {.inline.} =
     panic(message)
 
-  func sysFatal(exceptn: typedesc, message, arg: string) {.inline.} =
+  func sysFatal(exceptn: typedesc[Defect], message, arg: string) {.inline.} =
     rawoutput(message)
     panic(arg)
 
-elif (quirkyExceptions or defined(nimPanics)) and not defined(nimscript):
+elif quirkyExceptions and not defined(nimscript):
   import ansi_c
 
   func name(t: typedesc): string {.magic: "TypeTrait".}
 
-  func sysFatal(exceptn: typedesc, message, arg: string) {.inline, noreturn.} =
+  func sysFatal(exceptn: typedesc[Defect], message, arg: string) {.inline, noreturn.} =
     when nimvm:
       # TODO when doAssertRaises works in CT, add a test for it
       raise (ref exceptn)(msg: message & arg)
@@ -45,14 +45,14 @@ elif (quirkyExceptions or defined(nimPanics)) and not defined(nimscript):
         cstderr.rawWrite buf
       rawQuit 1
 
-  func sysFatal(exceptn: typedesc, message: string) {.inline, noreturn.} =
+  func sysFatal(exceptn: typedesc[Defect], message: string) {.inline, noreturn.} =
     sysFatal(exceptn, message, "")
 
 else:
-  func sysFatal(exceptn: typedesc, message: string) {.inline, noreturn.} =
+  func sysFatal(exceptn: typedesc[Defect], message: string) {.inline, noreturn.} =
     raise (ref exceptn)(msg: message)
 
-  func sysFatal(exceptn: typedesc, message, arg: string) {.inline, noreturn.} =
+  func sysFatal(exceptn: typedesc[Defect], message, arg: string) {.inline, noreturn.} =
     raise (ref exceptn)(msg: message & arg)
 
 {.pop.}