Fix spurious warnings inside an unused generic class that instantiate…

…s the default specialization of itself

source/ast/Expression.cpp

@@ -222,10 +222,7 @@ const Expression& Expression::bindLValue(const ExpressionSyntax& lhs, const Type
     // Create a placeholder expression that will carry the type of the rhs.
     // Nothing will ever actually look at this expression, it's there only
     // to fill the space in the created AssignmentExpression.
-    SourceRange rhsRange{location, location};
-    auto rhsExpr = comp.emplace<EmptyArgumentExpression>(rhs, rhsRange);
-    if (rhsExpr->bad())
-        return badExpr(comp, nullptr);
+    auto rhsExpr = comp.emplace<EmptyArgumentExpression>(rhs, SourceRange{location, location});
 
     auto instance = context.getInstance();
     Expression* lhsExpr;

tests/unittests/ast/ClassTests.cpp

@@ -3445,3 +3445,41 @@ endmodule
     compilation.addSyntaxTree(tree);
     NO_COMPILATION_ERRORS;
 }
+
+TEST_CASE("Unused var checking intersected with generic classes -- GH #1142") {
+    auto tree = SyntaxTree::fromText(R"(
+class A #(type T);
+endclass
+
+class B #(type T);
+    task get((* unused *) output T t);
+    endtask
+endclass
+
+class C #(type T = int);
+    B #(T) b;
+    (* unused *) typedef A #(C) unused;
+
+    task test();
+        T t;
+        forever begin
+            b.get(t);
+            process(t);
+        end
+    endtask
+
+    function void process((* unused *) T t);
+    endfunction
+endclass
+
+module top;
+endmodule
+)");
+
+    CompilationOptions coptions;
+    coptions.flags = CompilationFlags::None;
+
+    Compilation compilation(coptions);
+    compilation.addSyntaxTree(tree);
+    NO_COMPILATION_ERRORS;
+}