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https://github.com/carbon-language/carbon-lang.git
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Support for passing C++ templates as arguments to template template parameters. (#6475)
Allow passing a C++ template as a template template argument to another C++ template. Does not allow passing a Carbon generic as an argument. Depends on #6474.
This commit is contained in:
Richard Smith
@@ -48,6 +48,29 @@ auto PerformCallToCppFunction(Context& context, SemIR::LocId loc_id,
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}
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}
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// Synthesize a placeholder `void{}` template argument, that will never be a
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// valid argument for any template parameter. This is used in order to get Clang
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// to diagnose invalid template argument errors for us. The location of the
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// Carbon expression is used as the location of the C++ expression, so
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// Clang's diagnostics will point into the Carbon code.
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//
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// TODO: If Clang ever tries to print the type of the expression or to
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// pretty-print the expression itself, it would print the wrong thing. Currently
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// this doesn't appear to happen, but in principle it could. Ideally we'd add an
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// extension point to Clang to represent a "foreign expression" and use it here
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// instead of creating a bogus placeholder expression.
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static auto MakePlaceholderTemplateArg(Context& context, SemIR::InstId arg_id)
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-> clang::TemplateArgumentLoc {
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auto arg_loc = GetCppLocation(context, SemIR::LocId(arg_id));
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auto void_type = context.ast_context().VoidTy;
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auto* arg = new (context.ast_context()) clang::CXXScalarValueInitExpr(
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void_type,
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context.ast_context().getTrivialTypeSourceInfo(void_type, arg_loc),
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arg_loc);
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return clang::TemplateArgumentLoc(
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clang::TemplateArgument(arg, /*IsCanonical=*/false), arg);
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}
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// Converts an argument in a call to a C++ template name into a corresponding
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// clang template argument, given the template parameter it will be matched
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// against.
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@@ -72,10 +95,22 @@ static auto ConvertArgToTemplateArg(Context& context,
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}
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if (isa<clang::TemplateTemplateParmDecl>(param_decl)) {
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// TODO: Check the type of the argument `CppTemplateNameType` and
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// convert it to a `clang::TemplateName`.
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context.TODO(arg_id, "argument for template template parameter");
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return std::nullopt;
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auto inst = context.sem_ir().insts().Get(arg_id);
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if (auto template_name_type =
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context.types().TryGetAs<SemIR::CppTemplateNameType>(
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inst.type_id())) {
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clang::TemplateName name(cast<clang::TemplateDecl>(
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context.clang_decls().Get(template_name_type->decl_id).key.decl));
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return clang::TemplateArgumentLoc(
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context.ast_context(), clang::TemplateArgument(name),
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/*TemplateKWLoc=*/clang::SourceLocation(),
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clang::NestedNameSpecifierLoc(),
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GetCppLocation(context, SemIR::LocId(arg_id)));
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}
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// TODO: Eventually we should also support passing Carbon generics as
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// template template arguments.
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return MakePlaceholderTemplateArg(context, arg_id);
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}
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if (isa<clang::NonTypeTemplateParmDecl>(param_decl)) {
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@@ -120,14 +155,7 @@ static auto ConvertArgsToTemplateArgs(Context& context,
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// placeholder template arguments so that Clang will diagnose it for us.
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for (auto arg_id : arg_ids) {
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// Synthesize a placeholder `void{}` template argument.
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auto arg_loc = GetCppLocation(context, SemIR::LocId(arg_id));
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auto void_type = context.ast_context().VoidTy;
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auto* arg = new (context.ast_context()) clang::CXXScalarValueInitExpr(
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void_type,
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context.ast_context().getTrivialTypeSourceInfo(void_type, arg_loc),
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arg_loc);
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arg_list.addArgument(clang::TemplateArgumentLoc(
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clang::TemplateArgument(arg, /*IsCanonical=*/false), arg));
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arg_list.addArgument(MakePlaceholderTemplateArg(context, arg_id));
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}
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return true;
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+64
-9
@@ -14,37 +14,92 @@
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template<typename> struct A {};
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template<typename> struct B {};
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template<typename, typename> struct C {};
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template<template<typename> typename, template<typename> typename>
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struct TwoTemplates {};
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// --- fail_todo_valid.carbon
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// --- valid.carbon
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library "[[@TEST_NAME]]";
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import Cpp library "templates.h";
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//@dump-sem-ir-begin
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// CHECK:STDERR: fail_todo_valid.carbon:[[@LINE+4]]:25: error: semantics TODO: `argument for template template parameter` [SemanticsTodo]
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// CHECK:STDERR: var x: Cpp.TwoTemplates(Cpp.A, Cpp.B);
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// CHECK:STDERR: ^~~~~
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// CHECK:STDERR:
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var x: Cpp.TwoTemplates(Cpp.A, Cpp.B);
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//@dump-sem-ir-end
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// --- fail_template_mismatch.carbon
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library "[[@TEST_NAME]]";
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import Cpp library "templates.h";
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//@dump-sem-ir-begin
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// CHECK:STDERR: fail_template_mismatch.carbon:[[@LINE+15]]:35: error: too few template arguments for class template 'C' [CppInteropParseError]
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// CHECK:STDERR: 22 | var x: Cpp.TwoTemplates(Cpp.A, Cpp.C);
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// CHECK:STDERR: | ^
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// CHECK:STDERR: fail_template_mismatch.carbon:[[@LINE+12]]:35: note: template template argument has different template parameters than its corresponding template template parameter [CppInteropParseNote]
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// CHECK:STDERR: 22 | var x: Cpp.TwoTemplates(Cpp.A, Cpp.C);
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// CHECK:STDERR: | ^
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// CHECK:STDERR: fail_template_mismatch.carbon:[[@LINE-9]]:10: in file included here [InCppInclude]
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// CHECK:STDERR: ./templates.h:6:66: note: previous template template parameter is here [CppInteropParseNote]
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// CHECK:STDERR: 6 | template<template<typename> typename, template<typename> typename>
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// CHECK:STDERR: | ~~~~~~~~~~~~~~~~~~ ^
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// CHECK:STDERR: fail_template_mismatch.carbon:[[@LINE-13]]:10: in file included here [InCppInclude]
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// CHECK:STDERR: ./templates.h:4:37: note: template is declared here [CppInteropParseNote]
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// CHECK:STDERR: 4 | template<typename, typename> struct C {};
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// CHECK:STDERR: | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
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// CHECK:STDERR:
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var x: Cpp.TwoTemplates(Cpp.A, Cpp.C);
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//@dump-sem-ir-end
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// --- fail_type_argument.carbon
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library "[[@TEST_NAME]]";
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import Cpp library "templates.h";
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class X {}
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// CHECK:STDERR: fail_type_argument.carbon:[[@LINE+4]]:32: error: template argument for template template parameter must be a class template or type alias template [CppInteropParseError]
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// CHECK:STDERR: 12 | var x: Cpp.TwoTemplates(Cpp.A, X);
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// CHECK:STDERR: | ^
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// CHECK:STDERR:
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var x: Cpp.TwoTemplates(Cpp.A, X);
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// --- fail_non_type_argument.carbon
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library "[[@TEST_NAME]]";
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import Cpp library "templates.h";
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// CHECK:STDERR: fail_non_type_argument.carbon:[[@LINE+4]]:25: error: semantics TODO: `argument for template template parameter` [SemanticsTodo]
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// CHECK:STDERR: var x: Cpp.TwoTemplates(Cpp.A, true);
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// CHECK:STDERR: ^~~~~
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// CHECK:STDERR: fail_non_type_argument.carbon:[[@LINE+4]]:32: error: template argument for template template parameter must be a class template or type alias template [CppInteropParseError]
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// CHECK:STDERR: 10 | var x: Cpp.TwoTemplates(Cpp.A, true);
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// CHECK:STDERR: | ^
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// CHECK:STDERR:
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var x: Cpp.TwoTemplates(Cpp.A, true);
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// CHECK:STDOUT: --- fail_todo_valid.carbon
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// CHECK:STDOUT: --- valid.carbon
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// CHECK:STDOUT:
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// CHECK:STDOUT: constants {
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// CHECK:STDOUT: %TwoTemplates: type = class_type @TwoTemplates [concrete]
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// CHECK:STDOUT: %pattern_type: type = pattern_type %TwoTemplates [concrete]
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// CHECK:STDOUT: }
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// CHECK:STDOUT:
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// CHECK:STDOUT: imports {
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// CHECK:STDOUT: }
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// CHECK:STDOUT:
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// CHECK:STDOUT: file {
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// CHECK:STDOUT: name_binding_decl {
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// CHECK:STDOUT: %x.patt: %pattern_type = ref_binding_pattern x [concrete]
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// CHECK:STDOUT: %x.var_patt: %pattern_type = var_pattern %x.patt [concrete]
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// CHECK:STDOUT: }
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// CHECK:STDOUT: %x.var: ref %TwoTemplates = var %x.var_patt [concrete]
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// CHECK:STDOUT: %x: ref %TwoTemplates = ref_binding x, %x.var [concrete = %x.var]
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// CHECK:STDOUT: }
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// CHECK:STDOUT:
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// CHECK:STDOUT: --- fail_template_mismatch.carbon
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// CHECK:STDOUT:
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// CHECK:STDOUT: constants {
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// CHECK:STDOUT: }
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