fixes #19078 [backport] (#19090)

compiler/condsyms.nim

@@ -138,3 +138,5 @@ proc initDefines*(symbols: StringTableRef) =
   defineSymbol("nimHasHintAll")
   defineSymbol("nimHasTrace")
   defineSymbol("nimHasEffectsOf")
+
+  defineSymbol("nimHasEnforceNoRaises")

compiler/pragmas.nim

@@ -31,7 +31,7 @@ const
     wAsmNoStackFrame, wDiscardable, wNoInit, wCodegenDecl,
     wGensym, wInject, wRaises, wEffectsOf, wTags, wLocks, wDelegator, wGcSafe,
     wConstructor, wLiftLocals, wStackTrace, wLineTrace, wNoDestroy,
-    wRequires, wEnsures}
+    wRequires, wEnsures, wEnforceNoRaises}
   converterPragmas* = procPragmas
   methodPragmas* = procPragmas+{wBase}-{wImportCpp}
   templatePragmas* = {wDeprecated, wError, wGensym, wInject, wDirty,
@@ -1237,6 +1237,8 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: var int,
         pragmaProposition(c, it)
       of wEnsures:
         pragmaEnsures(c, it)
+      of wEnforceNoRaises:
+        sym.flags.incl sfNeverRaises
       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",
+    wLiftLocals = "liftlocals", wEnforceNoRaises = "enforceNoRaises",
 
     wAuto = "auto", wBool = "bool", wCatch = "catch", wChar = "char",
     wClass = "class", wCompl = "compl", wConst_cast = "const_cast", wDefault = "default",

lib/std/private/digitsutils.nim

@@ -78,14 +78,17 @@ func addIntImpl(result: var string, x: uint64) {.inline.} =
     dec next
   addChars(result, tmp, next, tmp.len - next)
 
-func addInt*(result: var string, x: uint64) =
+when not defined(nimHasEnforceNoRaises):
+  {.pragma: enforceNoRaises.}
+
+func addInt*(result: var string, x: uint64) {.enforceNoRaises.} =
   when nimvm: addIntImpl(result, x)
   else:
     when not defined(js): addIntImpl(result, x)
     else:
       addChars(result, numToString(x))
 
-proc addInt*(result: var string; x: int64) =
+proc addInt*(result: var string; x: int64) {.enforceNoRaises.} =
   ## Converts integer to its string representation and appends it to `result`.
   runnableExamples:
     var s = "foo"
@@ -110,5 +113,5 @@ proc addInt*(result: var string; x: int64) =
       addChars(result, numToString(x))
     else: impl()
 
-proc addInt*(result: var string; x: int) {.inline.} =
+proc addInt*(result: var string; x: int) {.inline, enforceNoRaises.} =
   addInt(result, int64(x))