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Add initial support for non-type template parameters (#6740)

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This adds basic support for using templates with integer parameters.

https://github.com/carbon-language/carbon-lang/issues/6717
This commit is contained in:
Nicholas Bishop
2026-02-17 21:34:06 +00:00
committed by GitHub
parent 8a8dd01302
commit 6df9d5ba32
2 changed files with 112 additions and 21 deletions
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toolchain/check/cpp/call.cpp
+45 -4
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@@ -114,10 +114,51 @@ static auto ConvertArgToTemplateArg(Context& context,
return MakePlaceholderTemplateArg(context, arg_id);
}
if (isa<clang::NonTypeTemplateParmDecl>(param_decl)) {
// TODO: Check the argument has a concrete constant value, and convert it to
// a Clang constant value.
context.TODO(arg_id, "argument for non-type template parameter");
if (const auto* non_type =
dyn_cast<clang::NonTypeTemplateParmDecl>(param_decl)) {
auto param_type = non_type->getType();
// Handle integer parameters.
if (param_type->isIntegerType()) {
// Get the Carbon type corresponding to the parameter's Clang type.
const auto type_expr =
ImportCppType(context, SemIR::LocId(arg_id), param_type);
// Try to convert the argument to the parameter type.
const auto converted_inst_id =
Convert(context, SemIR::LocId(arg_id), arg_id,
{
.kind = ConversionTarget::Value,
.type_id = type_expr.type_id,
});
if (converted_inst_id == SemIR::ErrorInst::InstId) {
return std::nullopt;
}
auto const_inst_id =
context.constant_values().GetConstantInstId(converted_inst_id);
if (const_inst_id.has_value()) {
if (auto int_value =
context.insts().TryGetAs<SemIR::IntValue>(const_inst_id)) {
const auto& ap_int = context.ints().Get(int_value->int_id);
const bool is_unsigned =
!param_type->isSignedIntegerOrEnumerationType();
auto aps_int =
llvm::APSInt(ap_int, is_unsigned)
.extOrTrunc(context.ast_context().getIntWidth(param_type));
auto template_arg = clang::TemplateArgument(context.ast_context(),
aps_int, param_type);
// TODO: provide a better location.
auto loc = clang::TemplateArgumentLocInfo();
return clang::TemplateArgumentLoc(template_arg, loc);
}
}
}
// TODO: Support other types.
context.TODO(arg_id,
"unsupported argument type for non-type template parameter");
return std::nullopt;
}