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Use C++20 requires clauses in TypeNameGeneratorBase #8552

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Use C++20 requires clauses in TypeNameGeneratorBase 
This addresses the TODOs in src/wasm-type-printing.h by utilizing C++20
concepts and requires clauses.

- Replaced the manual SFINAE/macro-based check in TypeNameGeneratorBase
  with a static_assert(requires { ... }) to ensure subclasses implement
  getNames correctly. This is cleaner and more robust.
- Updated the ModuleTypeNameGenerator constructor to use a requires
  clause instead of std::enable_if_t for its default constructor,
  improving readability.
- Added #include <concepts> as required.
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@sbc100
sbc100 committed Mar 30, 2026
commit f30fd81d8cf72ce93a901bc1d10026d5392145ef
24 changes: 6 additions & 18 deletions src/wasm-type-printing.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
#ifndef wasm_wasm_type_printing_h
#define wasm_wasm_type_printing_h

#include <concepts>
#include <cstddef>
#include <iostream>
#include <unordered_map>
Expand All @@ -34,9 +35,6 @@ namespace wasm {
template<typename Subclass> struct TypeNameGeneratorBase {
TypeNameGeneratorBase() { assertValidUsage(); }

TypeNames getNames(HeapType type) {
WASM_UNREACHABLE("Derived class must implement getNames");
}
HeapType::Printed operator()(HeapType type) {
return type.print(
[&](HeapType ht) { return static_cast<Subclass*>(this)->getNames(ht); });
Expand All @@ -48,16 +46,9 @@ template<typename Subclass> struct TypeNameGeneratorBase {

private:
constexpr void assertValidUsage() {
// This check current causes a crash on MSVC
// TODO: Convert to C++20 requires check
#if !defined(_MSC_VER) && (!defined(__GNUC__) || __GNUC__ >= 14)
// Check that the subclass provides `getNames` with the correct type.
using Self = TypeNameGeneratorBase<Subclass>;
static_assert(
static_cast<TypeNames (Self::*)(HeapType)>(&Self::getNames) !=
static_cast<TypeNames (Self::*)(HeapType)>(&Subclass::getNames),
"Derived class must implement getNames");
#endif
static_assert(requires(Subclass& s, HeapType ht) {
{ s.getNames(ht) } -> std::same_as<TypeNames>;
}, "Derived class must implement getNames");
}
};

Expand Down Expand Up @@ -123,11 +114,8 @@ struct ModuleTypeNameGenerator
ModuleTypeNameGenerator(const Module& wasm, FallbackGenerator& fallback)
: wasm(wasm), fallback(fallback) {}

// TODO: Use C++20 `requires` to clean this up.
template<class T = FallbackGenerator>
ModuleTypeNameGenerator(
const Module& wasm,
std::enable_if_t<std::is_same_v<T, DefaultTypeNameGenerator>>* = nullptr)
ModuleTypeNameGenerator(const Module& wasm)
requires std::is_same_v<FallbackGenerator, DefaultTypeNameGenerator>
: ModuleTypeNameGenerator(wasm, defaultGenerator) {}

TypeNames getNames(HeapType type) {
Expand Down
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