Fix functions in generate block resulting in "Broken link in node" (#7236) (#7367)

Fixes #7236

src/V3AstNodeExpr.h

@@ -233,6 +233,7 @@ private:
     string m_dotted;  // Dotted part of scope the name()ed task/func is under or ""
     string m_inlinedDots;  // Dotted hierarchy flattened out
     bool m_pli = false;  // Pli system call ($name)
+    bool m_containsGenBlock = false;  // Contains gen block reference
     VIsCached m_purity;  // Pure state
 
 protected:
@@ -259,6 +260,8 @@ public:
     void classOrPackagep(AstNodeModule* nodep) { m_classOrPackagep = nodep; }
     bool pli() const { return m_pli; }
     void pli(bool flag) { m_pli = flag; }
+    bool containsGenBlock() const { return m_containsGenBlock; }
+    void containsGenBlock(const bool flag) { m_containsGenBlock = flag; }
     bool isPure() override;
 
     string emitVerilog() final override { V3ERROR_NA_RETURN(""); }

src/V3AstNodes.cpp

@@ -3111,6 +3111,7 @@ void AstActive::dumpJson(std::ostream& str) const { dumpJsonGen(str); }
 void AstNodeFTaskRef::dump(std::ostream& str) const {
     this->AstNodeExpr::dump(str);
     if (classOrPackagep()) str << " pkg=" << nodeAddr(classOrPackagep());
+    if (containsGenBlock()) str << " [GENBLK]";
     str << " -> ";
     if (dotted() != "") str << ".=" << dotted() << " ";
     if (taskp()) {
@@ -3121,6 +3122,7 @@ void AstNodeFTaskRef::dump(std::ostream& str) const {
 }
 void AstNodeFTaskRef::dumpJson(std::ostream& str) const {
     dumpJsonStrFunc(str, dotted);
+    dumpJsonBoolFuncIf(str, containsGenBlock);
     dumpJsonGen(str);
 }
 void AstNodeFTask::dump(std::ostream& str) const {

src/V3LinkDot.cpp

@@ -5067,6 +5067,17 @@ class LinkDotResolveVisitor final : public VNVisitor {
             m_ds.m_dotPos = DP_MEMBER;
         } else if (m_ds.m_dotp && m_ds.m_dotPos == DP_FINAL) {
             nodep->dotted(m_ds.m_dotText);  // Maybe ""
+            // Only flag FTaskRefs under generate-if/case blocks that may be
+            // pruned.  GenFor and plain begin-blocks won't be pruned by V3Param.
+            // VarXRef uses the broader m_genBlk flag (set for all GenBlocks)
+            // because genfor unrolling also removes variables.
+            if (m_ds.m_genBlk && m_ds.m_dotSymp) {
+                const AstNode* const blkp = m_ds.m_dotSymp->nodep();
+                if (VN_IS(blkp, GenBlock)
+                    && (VN_IS(blkp->backp(), GenIf) || VN_IS(blkp->backp(), GenCase))) {
+                    nodep->containsGenBlock(true);
+                }
+            }
         } else if (m_ds.m_dotp && m_ds.m_dotPos == DP_MEMBER) {
             // Found a Var, everything following is method call.
             // {scope}.{var}.HERE {method} ( ARGS )

src/V3Param.cpp

@@ -2529,6 +2529,14 @@ class ParamVisitor final : public VNVisitor {
         }
         return false;
     }
+    void visit(AstNodeFTaskRef* nodep) override {
+        if (nodep->containsGenBlock()) {
+            // Needs relink, as may remove pointed-to task/func
+            nodep->taskp(nullptr);
+            return;
+        }
+        iterateChildren(nodep);
+    }
     void visit(AstVarXRef* nodep) override {
         if (nodep->containsGenBlock()) {
             // Needs relink, as may remove pointed-to var

test_regress/t/t_function_generate.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of either the GNU Lesser General Public License Version 3
+# or the Perl Artistic License Version 2.0.
+# SPDX-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile(verilator_flags2=["--binary"])
+
+test.execute()
+
+test.passes()

test_regress/t/t_function_generate.v

@@ -0,0 +1,35 @@
+// DESCRIPTION: Verilator: Verify function calls through generate-if block references
+//
+// When a function is defined inside a generate-if block and called via a
+// dotted reference (e.g. defs.foo()), the FUNCREF must survive generate
+// pruning.  Previously the FUNCREF could point to the deleted else-branch
+// function, causing a broken-link internal error.
+//
+// This program is free software; you can redistribute it and/or modify it
+// under the terms of either the GNU Lesser General Public License Version 3
+// or the Perl Artistic License Version 2.0.
+// SPDX-FileCopyrightText: 2026 Wilson Snyder
+// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+module t(/*AUTOARG*/);
+  generate
+    if (1) begin : defs
+      function automatic logic foo;
+        foo = 1'b1;
+      endfunction
+    end else begin : defs
+      function automatic logic foo;
+        foo = 1'b0;
+      endfunction
+    end
+  endgenerate
+
+  initial begin
+    if (defs.foo() !== 1'b1) begin
+      $display("%%Error: defs.foo() returned wrong value");
+      $stop;
+    end
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+endmodule