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Fix crash attempting constant evaluation of a constexpr constructor. (#7514)

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We can't use a `CallExpr` to call a constructor; use a
`CXXConstructExpr` instead. While this fixes the crash and gets us past
the initial constant evaluation, we still can't map the constant value
back into Carbon, so this doesn't actually make constexpr constructors
work yet. But it does stop Clang from crashing.

Fixes #7498.
This commit is contained in:
Richard Smith
2026-07-16 15:17:08 +00:00
committed by GitHub
parent 703529fc55
commit 90f6654b48
2 changed files with 176 additions and 21 deletions
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toolchain/check/cpp/constant.cpp
+31 -21
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@@ -226,22 +226,7 @@ auto EvalCppCall(Context& context, SemIR::LocId loc_id,
const auto& args = context.inst_blocks().Get(args_id);
auto* function_decl = cast<clang::FunctionDecl>(clang_decl.decl());
// Create expr for the function declaration.
auto* decl_ref_expr = clang::DeclRefExpr::Create(
context.ast_context(), /*QualifierLoc=*/clang::NestedNameSpecifierLoc(),
/*TemplateKWLoc=*/clang::SourceLocation(), function_decl,
/*RefersToEnclosingVariableOrCapture=*/false,
/*NameLoc=*/GetCppLocation(context, loc_id), function_decl->getType(),
clang::VK_LValue);
// Cast to a function pointer type.
auto function_ptr_type =
context.ast_context().getPointerType(function_decl->getType());
auto* implicit_cast_expr = clang::ImplicitCastExpr::Create(
context.ast_context(), function_ptr_type,
clang::CK_FunctionToPointerDecay, decl_ref_expr, nullptr,
clang::VK_PRValue, clang::FPOptionsOverride());
auto loc = GetCppLocation(context, loc_id);
// Convert the arguments to exprs.
clang::SmallVector<clang::Expr*> arg_exprs;
@@ -256,11 +241,36 @@ auto EvalCppCall(Context& context, SemIR::LocId loc_id,
}
// Create an expr to call the function.
auto* call_expr = clang::CallExpr::Create(
context.ast_context(), implicit_cast_expr, arg_exprs,
function_decl->getCallResultType(), clang::VK_PRValue,
/*RParenLoc=*/GetCppLocation(context, loc_id),
clang::FPOptionsOverride());
clang::Expr* call_expr;
if (auto* ctor = dyn_cast<clang::CXXConstructorDecl>(function_decl)) {
// Constructor: generate a direct constructor call expression.
call_expr = clang::CXXConstructExpr::Create(
context.ast_context(), function_decl->getCallResultType(), loc, ctor,
/*Elidable=*/false, arg_exprs, /*HadMultipleCandidates=*/false,
/*ListInitialization=*/false, /*StdInitListInitialization=*/false,
/*ZeroInitialization=*/false, clang::CXXConstructionKind::Complete,
clang::SourceRange(loc));
} else {
// Create expr for the function declaration.
auto* decl_ref_expr = clang::DeclRefExpr::Create(
context.ast_context(), /*QualifierLoc=*/clang::NestedNameSpecifierLoc(),
/*TemplateKWLoc=*/clang::SourceLocation(), function_decl,
/*RefersToEnclosingVariableOrCapture=*/false,
/*NameLoc=*/loc, function_decl->getType(), clang::VK_LValue);
// Cast to a function pointer type.
// TODO: For a non-static member function, we should create a member access.
auto function_ptr_type =
context.ast_context().getPointerType(function_decl->getType());
auto* implicit_cast_expr = clang::ImplicitCastExpr::Create(
context.ast_context(), function_ptr_type,
clang::CK_FunctionToPointerDecay, decl_ref_expr, nullptr,
clang::VK_PRValue, clang::FPOptionsOverride());
call_expr = clang::CallExpr::Create(
context.ast_context(), implicit_cast_expr, arg_exprs,
function_decl->getCallResultType(), clang::VK_PRValue,
/*RParenLoc=*/loc, clang::FPOptionsOverride());
}
// Evaluate the expr as a constant and map that to Carbon constant.
clang::SmallVector<clang::PartialDiagnosticAt> notes;