Fix potentially unbounded loop of resolving bind directives that plac…

…e new bind directives into the same scope

scripts/diagnostics.txt

@@ -495,6 +495,7 @@ error VirtualInterfaceIfaceMember "virtual interfaces cannot be used as the type
 error DefparamBadHierarchy "defparam in a hierarchy in or under a generate block, array of instances, or bind instantiation cannot change a parameter value outside that hierarchy"
 error BindTargetPrimitive "cannot bind a primitive"
 error BindUnderBind "cannot bind an instance underneath the scope of another bind instance"
+error DuplicateBind "bind directive targeting the same scope instantiated more than once"
 error UdpWrongInputCount "incorrect number of input fields in table row; have {} but expect {}"
 error UdpDupDiffOutput "primitive table row duplicates a set of inputs with a different specified output value"
 error UdpAllX "primitive table row has all 'x' inputs so its output must also be 'x'"

source/ast/Scope.cpp

@@ -1123,8 +1123,14 @@ void Scope::elaborate() const {
     // If there are bind directives, reach up into the instance body
     // and pull out the extra bind metadata from its override node.
     if (hasBinds) {
+        SmallSet<const BindDirectiveSyntax*, 4> seenBindDirectives;
         ASTContext context(*this, LookupLocation::max);
         auto handleBind = [&](const BindDirectiveInfo& info) {
+            if (!seenBindDirectives.emplace(info.bindSyntax).second) {
+                addDiag(diag::DuplicateBind, info.bindSyntax->sourceRange());
+                return;
+            }
+
             SmallVector<const Symbol*> instances;
             SmallVector<const Symbol*> implicitNets;
             if (info.bindSyntax->instantiation->kind == SyntaxKind::CheckerInstantiation) {

tests/unittests/ast/HierarchyTests.cpp

@@ -1732,6 +1732,23 @@ bind p program p(s
     compilation.getAllDiagnostics();
 }
 
+TEST_CASE("Bind corner case crash regress 4") {
+    auto tree = SyntaxTree::fromText(R"(
+module m3;
+    module m2;
+        bind m2 m2 mc();
+    endmodule
+endmodule
+)");
+
+    Compilation compilation;
+    compilation.addSyntaxTree(tree);
+
+    auto& diags = compilation.getAllDiagnostics();
+    REQUIRE(diags.size() == 1);
+    CHECK(diags[0].code == diag::DuplicateBind);
+}
+
 TEST_CASE("Nested modules with binds, parameterized, info task") {
     auto tree = SyntaxTree::fromText(R"(
 module m #(parameter P);