fixes #20026; marks system procs which can raise defects (#20864)

* marks system procs which can raise defects

* add tests

* add more systemRaisesDefect

* add comment

compiler/ast.nim

@@ -299,6 +299,7 @@ type
     sfInjectDestructors # whether the proc needs the 'injectdestructors' transformation
     sfNeverRaises     # proc can never raise an exception, not even OverflowDefect
                       # or out-of-memory
+    sfSystemRaisesDefect # proc in the system can raise defects
     sfUsedInFinallyOrExcept  # symbol is used inside an 'except' or 'finally'
     sfSingleUsedTemp  # For temporaries that we know will only be used once
     sfNoalias         # 'noalias' annotation, means C's 'restrict'

compiler/ccgcalls.nim

@@ -14,7 +14,8 @@ proc canRaiseDisp(p: BProc; n: PNode): bool =
   if n.kind == nkSym and {sfNeverRaises, sfImportc, sfCompilerProc} * n.sym.flags != {}:
     result = false
   elif optPanics in p.config.globalOptions or
-      (n.kind == nkSym and sfSystemModule in getModule(n.sym).flags):
+      (n.kind == nkSym and sfSystemModule in getModule(n.sym).flags and
+       sfSystemRaisesDefect notin n.sym.flags):
     # we know we can be strict:
     result = canRaise(n)
   else:

compiler/condsyms.nim

@@ -147,3 +147,4 @@ proc initDefines*(symbols: StringTableRef) =
   defineSymbol("nimHasAmbiguousEnumHint")
 
   defineSymbol("nimHasOutParams")
+  defineSymbol("nimHasSystemRaisesDefect")

compiler/pragmas.nim

@@ -34,7 +34,7 @@ const
     wAsmNoStackFrame, wDiscardable, wNoInit, wCodegenDecl,
     wGensym, wInject, wRaises, wEffectsOf, wTags, wForbids, wLocks, wDelegator, wGcSafe,
     wConstructor, wLiftLocals, wStackTrace, wLineTrace, wNoDestroy,
-    wRequires, wEnsures, wEnforceNoRaises}
+    wRequires, wEnsures, wEnforceNoRaises, wSystemRaisesDefect}
   converterPragmas* = procPragmas
   methodPragmas* = procPragmas+{wBase}-{wImportCpp}
   templatePragmas* = {wDeprecated, wError, wGensym, wInject, wDirty,
@@ -1229,6 +1229,8 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: var int,
         pragmaEnsures(c, it)
       of wEnforceNoRaises:
         sym.flags.incl sfNeverRaises
+      of wSystemRaisesDefect:
+        sym.flags.incl sfSystemRaisesDefect
       else: invalidPragma(c, it)
     elif comesFromPush and whichKeyword(ident) != wInvalid:
       discard "ignore the .push pragma; it doesn't apply"

compiler/wordrecg.nim

@@ -86,7 +86,7 @@ type
     wAsmNoStackFrame = "asmNoStackFrame", wImplicitStatic = "implicitStatic",
     wGlobal = "global", wCodegenDecl = "codegenDecl", wUnchecked = "unchecked",
     wGuard = "guard", wLocks = "locks", wPartial = "partial", wExplain = "explain",
-    wLiftLocals = "liftlocals", wEnforceNoRaises = "enforceNoRaises",
+    wLiftLocals = "liftlocals", wEnforceNoRaises = "enforceNoRaises", wSystemRaisesDefect = "systemRaisesDefect",
     wRedefine = "redefine", wCallsite = "callsite",
 
     wAuto = "auto", wBool = "bool", wCatch = "catch", wChar = "char",