fix #18977; disallow change branch of an object variant in ORC (#21526)

* fix #18977 disallow change branch of an object variant in ORC

* check errors for goto exception

* fixes conditions

* fixes tests

* add a test case for #18977

compiler/ccgstmts.nim

@@ -1579,6 +1579,8 @@ proc genDiscriminantCheck(p: BProc, a, tmp: TLoc, objtype: PType,
         "#FieldDiscriminantCheck((NI)(NU)($1), (NI)(NU)($2), $3, $4);$n",
         [rdLoc(a), rdLoc(tmp), discriminatorTableName(p.module, t, field),
          lit])
+  if p.config.exc == excGoto:
+    raiseExit(p)
 
 when false:
   proc genCaseObjDiscMapping(p: BProc, e: PNode, t: PType, field: PSym; d: var TLoc) =
@@ -1603,7 +1605,7 @@ proc asgnFieldDiscriminant(p: BProc, e: PNode) =
   initLocExpr(p, e[0], a)
   getTemp(p, a.t, tmp)
   expr(p, e[1], tmp)
-  if optTinyRtti notin p.config.globalOptions and p.inUncheckedAssignSection == 0:
+  if p.inUncheckedAssignSection == 0:
     let field = dotExpr[1].sym
     genDiscriminantCheck(p, a, tmp, dotExpr[0].typ, field)
     message(p.config, e.info, warnCaseTransition)

compiler/injectdestructors.nim

@@ -17,12 +17,12 @@ import
   intsets, strtabs, ast, astalgo, msgs, renderer, magicsys, types, idents,
   strutils, options, lowerings, tables, modulegraphs,
   lineinfos, parampatterns, sighashes, liftdestructors, optimizer,
-  varpartitions, aliasanalysis, dfa
+  varpartitions, aliasanalysis, dfa, wordrecg
 
 when defined(nimPreviewSlimSystem):
   import std/assertions
 
-from trees import exprStructuralEquivalent, getRoot
+from trees import exprStructuralEquivalent, getRoot, whichPragma
 
 type
   Con = object
@@ -35,6 +35,7 @@ type
     idgen: IdGenerator
     body: PNode
     otherUsage: TLineInfo
+    inUncheckedAssignSection: int
 
   Scope = object # we do scope-based memory management.
     # a scope is comparable to an nkStmtListExpr like
@@ -342,15 +343,16 @@ It is best to factor out piece of object that needs custom destructor into separ
       return
 
     # generate: if le != tmp: `=destroy`(le)
-    let branchDestructor = produceDestructorForDiscriminator(c.graph, objType, leDotExpr[1].sym, n.info, c.idgen)
-    let cond = newNodeIT(nkInfix, n.info, getSysType(c.graph, unknownLineInfo, tyBool))
-    cond.add newSymNode(getMagicEqSymForType(c.graph, le.typ, n.info))
-    cond.add le
-    cond.add tmp
-    let notExpr = newNodeIT(nkPrefix, n.info, getSysType(c.graph, unknownLineInfo, tyBool))
-    notExpr.add newSymNode(createMagic(c.graph, c.idgen, "not", mNot))
-    notExpr.add cond
-    result.add newTree(nkIfStmt, newTree(nkElifBranch, notExpr, c.genOp(branchDestructor, le)))
+    if c.inUncheckedAssignSection != 0:
+      let branchDestructor = produceDestructorForDiscriminator(c.graph, objType, leDotExpr[1].sym, n.info, c.idgen)
+      let cond = newNodeIT(nkInfix, n.info, getSysType(c.graph, unknownLineInfo, tyBool))
+      cond.add newSymNode(getMagicEqSymForType(c.graph, le.typ, n.info))
+      cond.add le
+      cond.add tmp
+      let notExpr = newNodeIT(nkPrefix, n.info, getSysType(c.graph, unknownLineInfo, tyBool))
+      notExpr.add newSymNode(createMagic(c.graph, c.idgen, "not", mNot))
+      notExpr.add cond
+      result.add newTree(nkIfStmt, newTree(nkElifBranch, notExpr, c.genOp(branchDestructor, le)))
   result.add newTree(nkFastAsgn, le, tmp)
 
 proc genWasMoved(c: var Con, n: PNode): PNode =
@@ -877,7 +879,7 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode; tmpFlags = {sfSing
        nkTypeOfExpr, nkMixinStmt, nkBindStmt:
       result = n
 
-    of nkStringToCString, nkCStringToString, nkChckRangeF, nkChckRange64, nkChckRange, nkPragmaBlock:
+    of nkStringToCString, nkCStringToString, nkChckRangeF, nkChckRange64, nkChckRange:
       result = shallowCopy(n)
       for i in 0 ..< n.len:
         result[i] = p(n[i], c, s, normal)
@@ -885,6 +887,25 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode; tmpFlags = {sfSing
         if mode == normal:
           result = ensureDestruction(result, n, c, s)
 
+    of nkPragmaBlock:
+      var inUncheckedAssignSection = 0
+      let pragmaList = n[0]
+      for pi in pragmaList:
+        if whichPragma(pi) == wCast:
+          case whichPragma(pi[1])
+          of wUncheckedAssign:
+            inUncheckedAssignSection = 1
+          else:
+            discard
+      result = shallowCopy(n)
+      inc c.inUncheckedAssignSection, inUncheckedAssignSection
+      for i in 0 ..< n.len:
+        result[i] = p(n[i], c, s, normal)
+      dec c.inUncheckedAssignSection, inUncheckedAssignSection
+      if n.typ != nil and hasDestructor(c, n.typ):
+        if mode == normal:
+          result = ensureDestruction(result, n, c, s)
+
     of nkHiddenSubConv, nkHiddenStdConv, nkConv:
       # we have an "ownership invariance" for all constructors C(x).
       # See the comment for nkBracket construction. If the caller wants