Add error on zero/negative unpacked dimensions (#1642).

src/V3AstNodeOther.h

@@ -2720,7 +2720,7 @@ public:
 
 // === AstNodeRange ===
 class AstBracketRange final : public AstNodeRange {
-    // Parser only concept "[lhsp]", an AstUnknownRange, QueueRange or Range,
+    // Parser only concept C-style "[lhsp]", an AstUnknownRange, QueueRange or Range,
     // unknown until lhsp type is determined
     // @astgen op1 := elementsp : AstNode<AstNodeExpr|AstNodeDType>
 public:
@@ -2740,9 +2740,11 @@ class AstRange final : public AstNodeRange {
     // Range specification, for use under variables and cells
     // @astgen op1 := leftp : AstNodeExpr
     // @astgen op2 := rightp : AstNodeExpr
+    const bool m_fromBracket = false;  // From C-style '[x]' declaration
 public:
-    AstRange(FileLine* fl, AstNodeExpr* leftp, AstNodeExpr* rightp)
-        : ASTGEN_SUPER_Range(fl) {
+    AstRange(FileLine* fl, AstNodeExpr* leftp, AstNodeExpr* rightp, bool fromBracket = false)
+        : ASTGEN_SUPER_Range(fl)
+        , m_fromBracket{fromBracket} {
         this->leftp(leftp);
         this->rightp(rightp);
     }
@@ -2766,7 +2768,11 @@ public:
     void dump(std::ostream& str) const override;
     void dumpJson(std::ostream& str) const override;
     virtual string emitC() { V3ERROR_NA_RETURN(""); }
-    bool sameNode(const AstNode* /*samep*/) const override { return true; }
+    bool sameNode(const AstNode* samep) const override {
+        const AstRange* const asamep = VN_DBG_AS(samep, Range);
+        return fromBracket() == asamep->fromBracket();
+    }
+    bool fromBracket() const { return m_fromBracket; }
 };
 class AstUnsizedRange final : public AstNodeRange {
     // Unsized range specification, for open arrays

src/V3AstNodes.cpp

@@ -2217,10 +2217,12 @@ void AstNodeRange::dump(std::ostream& str) const { this->AstNode::dump(str); }
 void AstNodeRange::dumpJson(std::ostream& str) const { dumpJsonGen(str); }
 void AstRange::dump(std::ostream& str) const {
     this->AstNodeRange::dump(str);
+    if (fromBracket()) str << " [FB]";
     if (ascending()) str << " [ASCENDING]";
 }
 void AstRange::dumpJson(std::ostream& str) const {
     dumpJsonBoolFunc(str, ascending);
+    dumpJsonBoolFunc(str, fromBracket);
     dumpJsonGen(str);
 }
 void AstParamTypeDType::dump(std::ostream& str) const {

src/V3Width.cpp

@@ -961,7 +961,14 @@ class WidthVisitor final : public VNVisitor {
         if (m_vup->prelim()) {
             // Don't need to iterate because V3Const already constified
             const int width = nodep->elementsConst();
-            if (width > (1 << 28)) {
+            if (nodep->fromBracket() && nodep->leftConst() > nodep->rightConst()) {
+                // From a C-Style '[size]' declaration, due to range handling a '[-1]'
+                // will get transformed to look like a '[0:1]', instead report as error
+                // now we know the datatype is used
+                nodep->v3error("Size of range is '["
+                               << (-width + 2)
+                               << "]', must be positive integer (IEEE 1800-2023 7.4.2)");
+            } else if (width > (1 << 28)) {
                 nodep->v3error("Width of bit range is huge; vector of over 1 billion bits: 0x"
                                << std::hex << width << std::dec);
             }
@@ -1921,7 +1928,7 @@ class WidthVisitor final : public VNVisitor {
         // Cleanup array size
         userIterateAndNext(nodep->rangep(), WidthVP{SELF, BOTH}.p());
         nodep->dtypep(nodep);  // The array itself, not subDtype
-        if (auto* const adtypep = VN_CAST(nodep, UnpackArrayDType)) {
+        if (AstUnpackArrayDType* const adtypep = VN_CAST(nodep, UnpackArrayDType)) {
             // Historically array elements have width of the ref type not the full array
             nodep->widthFromSub(nodep->subDTypep());
             if (nodep->subDTypep()->skipRefp()->isCompound()) adtypep->isCompound(true);
@@ -1964,7 +1971,8 @@ class WidthVisitor final : public VNVisitor {
                 nodep->fileline(), VFlagChildDType{}, childp,
                 new AstRange{nodep->fileline(), new AstConst(elementsp->fileline(), 0),
                              new AstSub{elementsNewFl, VN_AS(elementsp, NodeExpr),
-                                        new AstConst(elementsNewFl, 1)}}};
+                                        new AstConst(elementsNewFl, 1)},
+                             true}};
         }
         nodep->replaceWith(newp);
         VL_DO_DANGLING(nodep->deleteTree(), nodep);

src/verilog.y

@@ -3189,7 +3189,7 @@ instRangeList<nodeRangep>:
 
 instRange<nodeRangep>:
                 '[' constExpr ']'
-                        { $$ = new AstRange{$1, new AstConst{$1, 0}, new AstSub{$1, $2, new AstConst{$1, 1}}}; }
+                        { $$ = new AstRange{$1, new AstConst{$1, 0}, new AstSub{$1, $2, new AstConst{$1, 1}}, true}; }
         |       '[' constExpr ':' constExpr ']'
                         { $$ = new AstRange{$1, $2, $4}; }
         ;