Add internal assertion that VarScopes properly formed.

src/V3Broken.cpp

@@ -238,6 +238,8 @@ public:
 // Broken state, as a visitor of each AstNode
 
 class BrokenCheckVisitor : public AstNVisitor {
+    bool m_inScope = false;  // Under AstScope
+
 private:
     static void checkWidthMin(const AstNode* nodep) {
         UASSERT_OBJ(nodep->width() == nodep->widthMin()
@@ -278,6 +280,22 @@ private:
                       && !VN_CAST(nodep->lhsp(), NodeVarRef)->access().isWriteOrRW()),
                     nodep, "Assignment LHS is not an lvalue");
     }
+    virtual void visit(AstScope* nodep) override {
+        VL_RESTORER(m_inScope);
+        {
+            m_inScope = true;
+            processAndIterate(nodep);
+        }
+    }
+    virtual void visit(AstNodeVarRef* nodep) override {
+        processAndIterate(nodep);
+        // m_inScope because some Vars have initial variable references without scopes
+        // This might false fire with some debug flags, as not certain we don't have temporary
+        // clear varScopep's during some an infrequent dump just before we re-LinkDot.
+        UASSERT_OBJ(
+            !(v3Global.assertScoped() && m_inScope && nodep->varp() && !nodep->varScopep()), nodep,
+            "VarRef missing VarScope pointer");
+    }
     virtual void visit(AstNode* nodep) override {
         // Process not just iterate
         processAndIterate(nodep);

src/V3Descope.cpp

@@ -304,6 +304,7 @@ public:
 
 void V3Descope::descopeAll(AstNetlist* nodep) {
     UINFO(2, __FUNCTION__ << ": " << endl);
+    v3Global.assertScoped(false);
     { DescopeVisitor visitor(nodep); }  // Destruct before checking
     V3Global::dumpCheckGlobalTree("descope", 0, v3Global.opt.dumpTreeLevel(__FILE__) >= 3);
 }

src/V3Global.h

@@ -95,6 +95,7 @@ class V3Global {
 
     int m_debugFileNumber = 0;  // Number to append to debug files created
     bool m_assertDTypesResolved = false;  // Tree should have dtypep()'s
+    bool m_assertScoped = false;  // Tree is scoped
     bool m_constRemoveXs = false;  // Const needs to strip any Xs
     bool m_needHeavy = false;  // Need verilated_heavy.h include
     bool m_needTraceDumper = false;  // Need __Vm_dumperp in symbols
@@ -125,6 +126,7 @@ public:
     AstNetlist* rootp() const { return m_rootp; }
     VWidthMinUsage widthMinUsage() const { return m_widthMinUsage; }
     bool assertDTypesResolved() const { return m_assertDTypesResolved; }
+    bool assertScoped() const { return m_assertScoped; }
 
     // METHODS
     void readFiles();
@@ -132,6 +134,7 @@ public:
     static void dumpCheckGlobalTree(const string& stagename, int newNumber = 0,
                                     bool doDump = true);
     void assertDTypesResolved(bool flag) { m_assertDTypesResolved = flag; }
+    void assertScoped(bool flag) { m_assertScoped = flag; }
     void widthMinUsage(const VWidthMinUsage& flag) { m_widthMinUsage = flag; }
     bool constRemoveXs() const { return m_constRemoveXs; }
     void constRemoveXs(bool flag) { m_constRemoveXs = flag; }

src/V3LinkDot.cpp

@@ -2947,6 +2947,7 @@ void V3LinkDot::linkDotGuts(AstNetlist* rootp, VLinkDotStep step) {
         // Well after the initial link when we're ready to operate on the flat design,
         // process AstScope's.  This needs to be separate pass after whole hierarchy graph created.
         LinkDotScopeVisitor visitors(rootp, &state);
+        v3Global.assertScoped(true);
         if (LinkDotState::debug() >= 5 || v3Global.opt.dumpTree() >= 9) {
             v3Global.rootp()->dumpTreeFile(v3Global.debugFilename("prelinkdot-scoped.tree"));
         }