refactor(semantic): remove redundant AST traversal filters

RecursiveASTVisitor already skips implicit decls and implicit
template instantiations by default via shouldVisitImplicitCode()
and shouldVisitTemplateInstantiations().

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Perdixky

src/semantic/filtered_ast_visitor.h

@@ -33,6 +33,8 @@ class FilteredASTVisitor : public clang::RecursiveASTVisitor<Derived> {
             return true;
         }
 
+        /// Clang doesn't visit implicit declarations and
+        /// implicit template instantiations by default.
         if(llvm::isa<clang::TranslationUnitDecl>(decl)) {
             if(interested_only) {
                 for(auto top: unit.top_level_decls()) {
@@ -46,29 +48,6 @@ class FilteredASTVisitor : public clang::RecursiveASTVisitor<Derived> {
             return Base::TraverseDecl(decl);
         }
 
-        if(decl->isImplicit()) {
-            return true;
-        }
-
-        /// We don't want to visit implicit instantiation.
-        if(auto SD = llvm::dyn_cast<clang::ClassTemplateSpecializationDecl>(decl)) {
-            if(SD->getSpecializationKind() == clang::TSK_ImplicitInstantiation) {
-                return true;
-            }
-        }
-
-        if(auto SD = llvm::dyn_cast<clang::FunctionDecl>(decl)) {
-            if(SD->getTemplateSpecializationKind() == clang::TSK_ImplicitInstantiation) {
-                return true;
-            }
-        }
-
-        if(auto SD = llvm::dyn_cast<clang::VarTemplateSpecializationDecl>(decl)) {
-            if(SD->getSpecializationKind() == clang::TSK_ImplicitInstantiation) {
-                return true;
-            }
-        }
-
         if constexpr(requires { getDerived().on_traverse_decl(decl, &Base::TraverseDecl); }) {
             return getDerived().on_traverse_decl(decl, &Base::TraverseDecl);
         } else {