Hover

Symbol Information

• Qualified name showing enclosing scope context (namespace, class)

• Symbol kind classification

• Access specifier (public / protected / private)

• Documentation comments (Doxygen)

• Source definition rendering

• Truncate large initializers in definition display (clangd#710)

  const int table[] = {0, 1, 2, /* ... 1000 elements ... */};
  // hover → show truncated definition, not the entire initializer

• Show virtual / override / final modifiers in hover (clangd#2474)

  struct Base {
      virtual void draw() = 0;
  };
  struct Circle : Base {
      void draw() override;  // hover should show "virtual void draw() override"
  };

• Show anonymous namespace in scope display (clangd#436)

  namespace { void helper(); }
  // hover on helper → scope: "(anonymous namespace)::"

Type Information

• Variable type with pretty-printing

• Desugared type (aka field) for type aliases

• Return type for functions/lambdas

• Function parameters with types, names, defaults

• Template parameters

• Deduced type on auto and decltype keyword hover

• Show deduced template arguments for CTAD variables (clangd#435)

  std::pair p(1, 3.14);
  // hover on p → "std::pair<int, double> p"

• Show template arguments for instantiations (clangd#230)

  template<typename T> T identity(T x) { return x; }
  identity(42);
  // hover → show "T = int" in template parameters

• Resolve lambda auto parameter types from call context (clangd#493)

  auto cmp = [](auto a, auto b) { return a < b; };
  std::sort(v.begin(), v.end(), cmp);
  // hover on a → "int" (deduced from std::sort<int>)

• Preserve sugared types for auto variables (clangd#709)

  auto it = vec.begin();
  // current:  "auto it" → "__gnu_cxx::__normal_iterator<int*, ...>"
  // expected: "auto it" → "std::vector<int>::iterator"

• Apply .clang-format style to printed type names (clangd#2156)

  // .clang-format: QualifierAlignment: Right
  const int* p;
  // current:  hover → "const int *p"
  // expected: hover → "int const *p"

• Correct hover for C typedef of anonymous struct (clangd#2219)

  typedef struct { int x, y; } Point;
  Point p;
  // current:  hover → "struct Point p" (misleading — no struct Point exists)
  // expected: hover → "Point p" (alias to anonymous struct)

• Concept and constrained auto hover showing constraint information

Layout Information

• Size (bits) for fields and types

• Offset within enclosing class

• Padding detection

• Alignment

• Show alignment and padding for type-level hover, not just fields (clangd#1763)

  struct Widget {
      int id;       // offset 0, size 32
      double value; // offset 64, size 64, padding 32
  };
  // hover on Widget → size: 128 bits, align: 64 bits, padding: 32 bits total

• Virtual function table offset for class methods (clangd#1771)

  struct Base {
      virtual void foo();  // hover → vtable offset: 0
      virtual void bar();  // hover → vtable offset: 1
  };

Expression Context

• Evaluated constant value (value field)

• Callee argument info (which parameter this maps to)

• Pass-by semantics (ref, const ref, value)

• Implicit conversion detection

• Show string literal length on hover (clangd#1016)

  const char* msg = "hello world";
  //                 ^^^^^^^^^^^^^ hover → length: 11 (excluding null terminator)

• Show numeric literal type on hover (clangd#1669)

  auto x = 42ULL;
  //       ^^^^^ hover → type: unsigned long long, value: 42
  auto y = 0x1p10;
  //       ^^^^^^ hover → type: double, value: 1024.0

• Avoid misleading expression value when hovering over record-type variables (clangd#1622)

  constexpr int N = 10;
  std::array<int, N> arr;
  arr[0];
  // hover on arr → should NOT show "value: 10" from enclosing expression

Documentation

• Resolve @copydoc Doxygen tags (clangd#1320)

  /// Detailed documentation.
  void base_func();
  
  /// @copydoc base_func()
  void wrapper();
  // hover on wrapper → show base_func's documentation

• Inherit documentation from overridden base methods (clangd#2504)

  struct Base {
      /// Renders the widget.
      virtual void draw();
  };
  struct Circle : Base {
      void draw() override;
      // hover → "Renders the widget." (inherited from Base::draw)
  };

• Share documentation across consecutive overloads (clangd#2506)

  /// Opens a file.
  void open(const char* path);
  void open(const char* path, int flags);
  // hover on second overload → "Opens a file." (shared from first)

• Documentation from inherited constructors (clangd#1936)

• Only associate comments directly above the declaration (clangd#974)

  // ==== Section Banner ====
  
  void foo();
  // hover on foo → should NOT show "==== Section Banner ===="

• Option to suppress misattributed doc comments (clangd#2148)

• Prefer declaration documentation over definition comments (clangd#829)

  // header.h:
  /// Public API documentation.
  void process(int x);
  
  // source.cpp:
  // internal implementation note
  void process(int x) { ... }
  // hover → show "Public API documentation.", not "internal implementation note"

• Preserve whitespace and newlines from comments (clangd#2057)

  /// | Column A | Column B |
  /// |----------|----------|
  /// | 1        | 2        |
  void table_fn();
  // hover → render the markdown table correctly, not as a single line

• Fix wrong indentation in hover comment rendering (clangd#1040)

• Docstrings missing when template keyword comes from macro expansion (clangd#1226)

• Synthesized documentation for trivial accessors (getters/setters)

Macro Hover

• Show macro expansion before definition (clangd#2642)

  #define MAX(a, b) ((a) > (b) ? (a) : (b))
  int z = MAX(x, y);
  //      ^^^^^^^^^ hover → expansion: "((x) > (y) ? (x) : (y))"
  //                         definition: "#define MAX(a, b) ((a) > (b) ? (a) : (b))"

Special Hover Targets

• Show struct/enum members on type-level hover (clangd#959)

  enum Color { Red, Green, Blue };
  // hover on Color → "enum Color { Red, Green, Blue }"

• Show underlying struct definition for typedef (clangd#2020)

  typedef struct { int x, y; } Point;
  Point p;
  // hover on Point → show the struct definition including members

• Keyword documentation on hover (clangd#1862)

  const int x = 42;
  // hover on "const" → description of the keyword

• Attribute documentation on hover (clangd#1862)

  [[nodiscard]] int compute();
  // hover on "nodiscard" → description of the attribute

• #include directive hover showing resolved header path

• this expression hover showing pointed-to type

• __func__ and related predefined identifier hover

• GTK-Doc, kernel-doc, and GObject Introspection documentation (clangd#2662)

• LaTeX rendering of Doxygen @f$ math formulas (clangd#2669)

Module-Related

• Hover on import statement shows module info
• Hover on module name shows owning file/partition list

Hover Correctness

Known issues that should be handled correctly:

• MSInheritanceAttr causing incorrect hover on MSVC targets (clangd#1643, clangd#2212)
• Object instantiation misidentified as function declaration (clangd#2225)
• Crash on large unsigned enum constant value (clangd#2381)
• Crash on function call hover with default arguments (clangd#551)
• Symbols shadowed by function-like macros with the same name (clangd#2490)

Changelog

Date	Change	PR
2025-06	Port clangd hover implementation	#452