diff --git a/include/Index/CSIF.h b/include/Index/CSIF.h
index d20902fa..20497712 100644
--- a/include/Index/CSIF.h
+++ b/include/Index/CSIF.h
@@ -71,7 +71,7 @@ struct Relation {
     /// The role of the relation.
     Role role;
     /// The range of the target, maybe empty.
-    // Range range;
+    protocol::Range range;
 };
 
 enum class SymbolKind {
diff --git a/include/Index/SymbolSlab.h b/include/Index/SymbolSlab.h
index 5e634270..531f28e6 100644
--- a/include/Index/SymbolSlab.h
+++ b/include/Index/SymbolSlab.h
@@ -6,24 +6,16 @@ namespace clice {
 
 class SymbolSlab {
 public:
+    CSIF index(clang::ASTContext& context);
+
+    std::size_t lookup(const clang::Decl* decl);
+
     SymbolSlab& addSymbol(const clang::Decl* decl);
 
     SymbolSlab& addOccurrence(const clang::Decl* decl, protocol::Range range, Role role);
 
     SymbolSlab& addRelation(const clang::Decl* from, const clang::Decl* to, Role role);
 
-    std::size_t lookup(const clang::Decl* decl) {
-        auto iter = cache.find(decl);
-        if(iter != cache.end()) {
-            return iter->second;
-        }
-
-        llvm::outs() << "SymbolSlab::lookup: decl not found\n";
-        std::terminate();
-    }
-
-    CSIF index(clang::ASTContext& context);
-
 private:
     llvm::BumpPtrAllocator allocator;
     llvm::StringSaver saver{allocator};
@@ -31,6 +23,8 @@ private:
     std::vector<Symbol> symbols;
     std::vector<Occurrence> occurrences;
     std::vector<std::vector<Relation>> relations;
+
+    llvm::DenseMap<SymbolID, std::size_t> symbolIndex;
     llvm::DenseMap<const clang::Decl*, std::size_t> cache;
 };
 
diff --git a/scripts/build-dev-test.sh b/scripts/build-dev-test.sh
index 7cc4afcc..2c219785 100755
--- a/scripts/build-dev-test.sh
+++ b/scripts/build-dev-test.sh
@@ -1 +1 @@
-cmake -B build -G Ninja -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang -DCMAKE_BUILD_TYPE=Debug -DCLICE_ENABLE_TEST=ON -DCMAKE_CXX_FLAGS="-fno-rtti -g -O0 -fsanitize=address"
\ No newline at end of file
+cmake -B build -G Ninja -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang -DCMAKE_BUILD_TYPE=Debug -DCLICE_ENABLE_TEST=ON -DCMAKE_CXX_FLAGS="-fno-rtti -g -O0"
\ No newline at end of file
diff --git a/src/Index/Index.cpp b/src/Index/Index.cpp
index 9a203472..64867357 100644
--- a/src/Index/Index.cpp
+++ b/src/Index/Index.cpp
@@ -9,7 +9,8 @@ class SymbolCollector : public clang::RecursiveASTVisitor<SymbolCollector> {
     using Base = clang::RecursiveASTVisitor<SymbolCollector>;
 
 public:
-    SymbolCollector(SymbolSlab& builder) : builder(builder) {}
+    SymbolCollector(SymbolSlab& slab, clang::ASTContext& context) :
+        slab(slab), context(context), srcMgr(context.getSourceManager()) {}
 
     bool TraverseDecl(clang::Decl* decl) {
         /// `TranslationUnitDecl` has invalid location information.
@@ -18,7 +19,18 @@ public:
             return Base::TraverseDecl(decl);
         }
 
-        builder.addSymbol(decl);
+        if(decl->isImplicit()) {
+            return true;
+        }
+
+        slab.addSymbol(decl);
+        llvm::outs() << "------------------------------------------\n";
+        decl->dump();
+
+        llvm::SmallString<128> USR;
+        clang::index::generateUSRForDecl(decl, USR);
+        llvm::outs() << "USR: " << USR << "\n";
+
         // TODO: generate SymbolID for every decl.
         // Distinguish linkage, for no or internal linkage.
         // For them, relation lookup is only occurred in current TU.
@@ -132,7 +144,30 @@ public:
     }
 
     VISIT_TYOELOC(TemplateSpecializationTypeLoc) {
-        auto range = loc.getTemplateNameLoc();
+        auto name = loc.getTypePtr()->getTemplateName().getUnderlying();
+        auto decl = name.getAsTemplateDecl();
+        if(auto CTD = llvm::dyn_cast<clang::ClassTemplateDecl>(decl)) {
+            auto nameLoc = loc.getTemplateNameLoc();
+            auto line = srcMgr.getPresumedLineNumber(nameLoc);
+            auto column = srcMgr.getPresumedColumnNumber(nameLoc);
+            protocol::Range range = {line,
+                                     column,
+                                     line,
+                                     static_cast<protocol::uinteger>(column + decl->getName().size())};
+
+            void* ptr = CTD;
+            clang::ClassTemplateSpecializationDecl* decl2 =
+                CTD->findSpecialization(loc.getTypePtr()->template_arguments(), ptr);
+            auto main = decl2->getSpecializedTemplateOrPartial();
+
+            if(main.is<clang::ClassTemplateDecl*>()) {
+                auto decl3 = main.get<clang::ClassTemplateDecl*>();
+                slab.addOccurrence(decl3, range, Role::ExplicitInstantiation);
+            } else {
+                auto decl3 = main.get<clang::ClassTemplatePartialSpecializationDecl*>();
+                slab.addOccurrence(decl3, range, Role::ExplicitInstantiation);
+            }
+        }
         return true;
     }
 
@@ -140,14 +175,16 @@ public:
     // MemberPointerTypeLoc
 
 private:
-    SymbolSlab& builder;
+    SymbolSlab& slab;
+    clang::ASTContext& context;
+    clang::SourceManager& srcMgr;
 };
 
 }  // namespace
 
 CSIF SymbolSlab::index(clang::ASTContext& context) {
     CSIF csif;
-    SymbolCollector collector(*this);
+    SymbolCollector collector(*this, context);
     collector.TraverseAST(context);
 
     csif.version = "0.1";
diff --git a/src/Index/SymbolSlab.cpp b/src/Index/SymbolSlab.cpp
index dfb16acd..366bedc8 100644
--- a/src/Index/SymbolSlab.cpp
+++ b/src/Index/SymbolSlab.cpp
@@ -3,20 +3,29 @@
 
 namespace clice {
 
+std::size_t SymbolSlab::lookup(const clang::Decl* decl) {
+    auto iter = cache.find(decl);
+    if(iter == cache.end()) {
+        llvm::outs() << "SymbolSlab::lookup: decl not found\n";
+        std::terminate();
+    }
+    return iter->second;
+}
+
 SymbolSlab& SymbolSlab::addSymbol(const clang::Decl* decl) {
     // Generate and save USR.
     llvm::SmallString<128> USR;
     clang::index::generateUSRForDecl(decl, USR);
-    saver.save(USR.str());
 
-    if(cache.contains(decl)) {
-        llvm::outs() << "SymbolSlab::addSymbol: decl already exists\n";
-        std::terminate();
+    if(!symbolIndex.contains(SymbolID::fromUSR(USR))) {
+        auto ID = SymbolID::fromUSR(saver.save(USR.str()));
+        symbols.emplace_back(ID);
+        cache.try_emplace(decl, symbols.size() - 1);
+        symbolIndex.try_emplace(ID, symbols.size() - 1);
+    } else {
+        cache.try_emplace(decl, symbolIndex[SymbolID::fromUSR(USR)]);
     }
 
-    auto index = symbols.size();
-    symbols.emplace_back(SymbolID::fromUSR(USR.str()));
-    cache.try_emplace(decl, index);
     return *this;
 }
 
diff --git a/tests/Index/Index.cpp b/tests/Index/Index.cpp
index 916721d7..daa2505e 100644
--- a/tests/Index/Index.cpp
+++ b/tests/Index/Index.cpp
@@ -2,6 +2,7 @@
 #include <Index/SymbolSlab.h>
 #include <Support/JSON.h>
 #include <Compiler/Compiler.h>
+#include <Support/FileSystem.h>
 
 using namespace clice;
 
@@ -14,13 +15,17 @@ TEST(clice, Index) {
         "/home/ykiko/C++/clice2/build/lib/clang/20",
     };
     const char* code = R"(
-template<typename T, typename U> struct X {};
+template<typename T, typename U> struct X {
+    using type = char;
+};
 
-template<typename T> struct X<T, T> {};
+template<typename T> struct X<T, T> {
+    using type = int;
+};
 
 void f() {
-    X<char, int> y;
-    X<int, int> x;
+    typename X<char, int>::type y;
+    typename X<int, int>::type x;
 }
 )";
 
@@ -29,5 +34,8 @@ void f() {
     SymbolSlab slab;
     auto csif = slab.index(compiler.context());
     auto value = json::serialize(csif);
+    std::error_code EC;
+    llvm::raw_fd_ostream fileStream("output.json", EC);
+    fileStream << value << "\n";
     llvm::outs() << value << "\n";
 }
diff --git a/tests/Source/ASTVisitor/test.cpp b/tests/Source/ASTVisitor/test.cpp
index 909cbc0a..0e1bd9c1 100644
--- a/tests/Source/ASTVisitor/test.cpp
+++ b/tests/Source/ASTVisitor/test.cpp
@@ -1,13 +1,14 @@
-namespace {
+template <typename T, typename U>
+struct X {
+    using type = char;
+};
+
 template <typename T>
-struct A {};
+struct X<T, T> {
+    using type = int;
+};
 
-template <>
-struct A<int> {};
-
-}  // namespace
-
-int main() {
-    A<int> a;
-    return 0;
+void f() {
+    typename X<char, int>::type y;
+    typename X<int, int>::type x;
 }