Ensure VarRef inherits dtype when varp is set.

Inlining used to set some VarRefs to point to new Var nodes, without
updating the dtype of the VarRef to the dtype of the new Var.
AstNode::sameTree does identity comparison on the dtype, so some trees
that were semantically the same did not compare as such with sameTree
because of the dtype. This in turn results in some missed opportunities
for combining equivalent SenTree sensitivities when the clock came from
outside.

src/V3Ast.h

@@ -2269,29 +2269,26 @@ private:
     string m_name;  // Name of variable
     string m_hiername;  // Scope converted into name-> for emitting
     bool m_hierThis;  // Hiername points to "this" function
-    void init();
 
 public:
     AstNodeVarRef(AstType t, FileLine* fl, const string& name, bool lvalue)
         : AstNodeMath(t, fl)
         , m_lvalue(lvalue)
-        , m_varp(NULL)
         , m_varScopep(NULL)
         , m_packagep(NULL)
         , m_name(name)
         , m_hierThis(false) {
-        init();
+        this->varp(NULL);
     }
     AstNodeVarRef(AstType t, FileLine* fl, const string& name, AstVar* varp, bool lvalue)
         : AstNodeMath(t, fl)
         , m_lvalue(lvalue)
-        , m_varp(varp)
         , m_varScopep(NULL)
         , m_packagep(NULL)
         , m_name(name)
         , m_hierThis(false) {
         // May have varp==NULL
-        init();
+        this->varp(varp);
     }
     ASTNODE_BASE_FUNCS(NodeVarRef)
     virtual bool hasDType() const { return true; }
@@ -2303,7 +2300,7 @@ public:
     bool lvalue() const { return m_lvalue; }
     void lvalue(bool lval) { m_lvalue = lval; }  // Avoid using this; Set in constructor
     AstVar* varp() const { return m_varp; }  // [After Link] Pointer to variable
-    void varp(AstVar* varp) { m_varp = varp; }
+    void varp(AstVar* varp);
     AstVarScope* varScopep() const { return m_varScopep; }
     void varScopep(AstVarScope* varscp) { m_varScopep = varscp; }
     string hiername() const { return m_hiername; }
@@ -2943,8 +2940,9 @@ inline bool AstNode::sameGateTree(const AstNode* node2p) const {
     return sameTreeIter(this, node2p, true, true);
 }
 
-inline void AstNodeVarRef::init() {
-    if (m_varp) dtypep(m_varp->dtypep());
+inline void AstNodeVarRef::varp(AstVar* varp) {
+    m_varp = varp;
+    dtypeFrom(varp);
 }
 
 inline bool AstNodeDType::isFourstate() const { return basicp()->isFourstate(); }

src/V3Inst.cpp

@@ -443,7 +443,6 @@ private:
                 string newname = varrefp->name() + "__BRA__" + cvtToStr(i + offset) + "__KET__";
                 AstVarXRef* newVarXRefp = new AstVarXRef(nodep->fileline(), newname, "", true);
                 newVarXRefp->varp(newp->modVarp());
-                newVarXRefp->dtypep(newp->modVarp()->dtypep());
                 newp->exprp()->unlinkFrBack()->deleteTree();
                 newp->exprp(newVarXRefp);
                 if (!prevPinp) {