Signature Help

Trigger Characters

Registered: (, ), {, }, <, >, ,

Character	Context	Behavior
`(`	Function call	Show overload signatures
`)`	Close paren	Update context
`{`	Brace init	Show overload signatures
`}`	Close brace	Update context
`<`	Template args	Show overload signatures
`>`	Template close	Update context
`,`	Argument separator	Update active parameter

Avoid false triggers — don't fire inside comments, string literals, or when defining a function (clangd#51, clangd#289)

cpp

void foo(int x, int y) {  // should NOT trigger signature help
//       ^^^^^^^^^^^^^ this is a definition, not a call

new expression with braces should trigger signature help (clangd#1967)

cpp

auto* w = new Widget{800, 600};
//                   ^ should trigger signature help for Widget constructors

Overload Signatures

Function overload signatures
Active parameter tracking
Template instantiation pattern resolution (shows template pattern, not instantiation)
Parameter labels with types
Return type in signature label
Parameter label byte offsets for precise highlighting

Filter const/non-const overload duplicates — don't show both when only one is viable (clangd#50)

cpp

struct Vec {
    int& operator[](size_t);
    const int& operator[](size_t) const;
};
Vec v;
v[0];  // only show non-const overload (v is non-const)

Prefer user-supplied constructors over compiler-generated ones (clangd#1259)

Filter dependent overload candidates by arity (clangd#2342)

cpp

template<typename T>
void process(T& obj) {
    obj.foo(1, 2);  // if T has foo(int) and foo(int,int), only show foo(int,int) as viable
}

Better heuristic resolution of dependent overloads (clangd#1083)

Strip C++23 explicit object parameter from displayed signatures (clangd#2284)

cpp

struct S { void f(this S& self, int x); };
S s;
s.f(^  // show "(int x)", not "(this S& self, int x)"

Special Call Contexts

Template argument signature help (clangd#299, clangd#1387)

cpp

template<typename Key, typename Value, typename Compare = less<Key>>
class SortedMap;

SortedMap<int, ^  // show: Key = int, Value = ?, Compare = less<Key>

Aggregate initialization — show field names as "parameters" (clangd#726, clangd#2541)

cpp

struct Point { int x, y, z; };
Point p = {1, ^  // show: .x = int, .y = int, .z = int (active: .y)

Inherited constructors — show base class constructors when calling from derived (clangd#1363)

cpp

struct Base { Base(int x, int y); };
struct Derived : Base { using Base::Base; };
Derived d(^  // show Base(int x, int y)

operator[] signature help (clangd#2472)

cpp

std::map<std::string, int> m;
m[^  // show operator[](const string& key)

Lambda calls — show lambda name instead of operator() (clangd#86)

cpp

auto validate = [](int x, int max) -> bool { ... };
validate(^  // show "validate(int x, int max) -> bool", not "operator()(int x, int max)"

Function pointer calls — show parameter names (clangd#1068, clangd#1729)

cpp

void (*callback)(int status, const char* msg);
callback(^  // show "(int status, const char* msg)"

Constructor signature help during object initialization

Macro function calls — show macro parameters, not the underlying expansion (clangd#795)

cpp

#define CHECK(cond, msg) do { if (!(cond)) fail(msg); } while(0)
CHECK(^  // show "CHECK(cond, msg)", not "fail(const char*)"

Parameter Display

Forwarding function parameter resolution — show underlying constructor parameters for std::make_unique, emplace_back, etc. (clangd#517)
cpp
```
struct Widget { Widget(int width, int height); };
std::make_unique<Widget>(^  // show "(int width, int height)"
```

Parameter pack display (clangd#638)

cpp

template<typename... Args>
void log(const char* fmt, Args&&... args);
log("x=%d y=%d", ^  // show "fmt, args..." with active parameter on args

Prettify standard library parameter names (clangd#736)

// current:  push_back(const value_type& __x)
// expected: push_back(const value_type& value)

Preserve enum class scope in parameter types (clangd#2475)

cpp

enum class Color { Red, Green, Blue };
void paint(Color c);
paint(^  // show "(Color c)", not "(c)" with scope stripped

Show default parameter values

cpp

void open(std::string path, int mode = 0644);
open("file", ^  // show "int mode = 0644" (active), user knows it can be omitted

Documentation

Documentation for the active parameter (from @param doc comments)

cpp

/// @param path The file system path.
/// @param mode POSIX file permission bits.
void open(std::string path, int mode);
open("file", ^  // show documentation for mode parameter

Respect documentationFormat capability (clangd#945)
Propagate documentation through inherited constructors (clangd#1936)
Overload set count indicator

Changelog

Date	Change	PR
—	Function overload signatures, active parameter tracking, trigger characters	—

Signature Help ​

Trigger Characters ​

Overload Signatures ​

Special Call Contexts ​

Parameter Display ​

Documentation ​