[backport] fixes #23711; C code contains backtick`gensym (#23716)

fixes #23711

compiler/ast.nim

@@ -41,7 +41,7 @@ type
   TNodeKinds* = set[TNodeKind]
 
 type
-  TSymFlag* = enum    # 51 flags!
+  TSymFlag* = enum    # 52 flags!
     sfUsed,           # read access of sym (for warnings) or simply used
     sfExported,       # symbol is exported from module
     sfFromGeneric,    # symbol is instantiation of a generic; this is needed
@@ -126,6 +126,7 @@ type
     sfByCopy          # param is marked as pass bycopy
     sfMember          # proc is a C++ member of a type
     sfCodegenDecl     # type, proc, global or proc param is marked as codegenDecl
+    sfWasGenSym       # symbol was 'gensym'ed
 
   TSymFlags* = set[TSymFlag]
 

compiler/evaltempl.nim

@@ -56,6 +56,7 @@ proc evalTemplateAux(templ, actual: PNode, c: var TemplCtx, result: PNode) =
           #  internalAssert c.config, false
           idTablePut(c.mapping, s, x)
         if sfGenSym in s.flags:
+          # TODO: getIdent(c.ic, "`" & x.name.s & "`gensym" & $c.instID)
           result.add newIdentNode(getIdent(c.ic, x.name.s & "`gensym" & $c.instID),
             if c.instLines: actual.info else: templ.info)
         else:

compiler/sem.nim

@@ -254,6 +254,8 @@ proc newSymG*(kind: TSymKind, n: PNode, c: PContext): PSym =
     result.owner = getCurrOwner(c)
   else:
     result = newSym(kind, considerQuotedIdent(c, n), c.idgen, getCurrOwner(c), n.info)
+    if find(result.name.s, '`') >= 0:
+      result.flags.incl sfWasGenSym
   #if kind in {skForVar, skLet, skVar} and result.owner.kind == skModule:
   #  incl(result.flags, sfGlobal)
   when defined(nimsuggest):
@@ -263,7 +265,7 @@ proc semIdentVis(c: PContext, kind: TSymKind, n: PNode,
                  allowed: TSymFlags): PSym
   # identifier with visibility
 proc semIdentWithPragma(c: PContext, kind: TSymKind, n: PNode,
-                        allowed: TSymFlags): PSym
+                        allowed: TSymFlags, fromTopLevel = false): PSym
 
 proc typeAllowedCheck(c: PContext; info: TLineInfo; typ: PType; kind: TSymKind;
                       flags: TTypeAllowedFlags = {}) =

compiler/semstmts.nim

@@ -480,7 +480,7 @@ proc identWithin(n: PNode, s: PIdent): bool =
 
 proc semIdentDef(c: PContext, n: PNode, kind: TSymKind, reportToNimsuggest = true): PSym =
   if isTopLevel(c):
-    result = semIdentWithPragma(c, kind, n, {sfExported})
+    result = semIdentWithPragma(c, kind, n, {sfExported}, fromTopLevel = true)
     incl(result.flags, sfGlobal)
     #if kind in {skVar, skLet}:
     #  echo "global variable here ", n.info, " ", result.name.s

compiler/semtypes.nim

@@ -540,7 +540,7 @@ proc semIdentVis(c: PContext, kind: TSymKind, n: PNode,
     result = newSymG(kind, n, c)
 
 proc semIdentWithPragma(c: PContext, kind: TSymKind, n: PNode,
-                        allowed: TSymFlags): PSym =
+                        allowed: TSymFlags, fromTopLevel = false): PSym =
   if n.kind == nkPragmaExpr:
     checkSonsLen(n, 2, c.config)
     result = semIdentVis(c, kind, n[0], allowed)
@@ -555,11 +555,15 @@ proc semIdentWithPragma(c: PContext, kind: TSymKind, n: PNode,
     else: discard
   else:
     result = semIdentVis(c, kind, n, allowed)
+    let invalidPragmasForPush = if fromTopLevel and sfWasGenSym notin result.flags:
+      {}
+    else:
+      {wExportc, wExportCpp, wDynlib}
     case kind
     of skField: implicitPragmas(c, result, n.info, fieldPragmas)
-    of skVar:   implicitPragmas(c, result, n.info, varPragmas)
-    of skLet:   implicitPragmas(c, result, n.info, letPragmas)
-    of skConst: implicitPragmas(c, result, n.info, constPragmas)
+    of skVar:   implicitPragmas(c, result, n.info, varPragmas-invalidPragmasForPush)
+    of skLet:   implicitPragmas(c, result, n.info, letPragmas-invalidPragmasForPush)
+    of skConst: implicitPragmas(c, result, n.info, constPragmas-invalidPragmasForPush)
     else: discard
 
 proc checkForOverlap(c: PContext, t: PNode, currentEx, branchIndex: int) =

tests/pragmas/tpush.nim

@@ -99,3 +99,28 @@ block: # bug #23019
   k(w)
   {.pop.}
   {.pop.}
+
+{.push exportC.}
+
+block:
+  proc foo11() =
+    const factor = [1, 2, 3, 4]
+    doAssert factor[0] == 1
+  proc foo21() =
+    const factor = [1, 2, 3, 4]
+    doAssert factor[0] == 1
+
+  foo11()
+  foo21()
+
+template foo31() =
+  let factor = [1, 2, 3, 4]
+  doAssert factor[0] == 1
+template foo41() =
+  let factor = [1, 2, 3, 4]
+  doAssert factor[0] == 1
+
+foo31()
+foo41()
+
+{.pop.}