swiftlang/swift

[SR-14443] [C++] Don't crash on invalid dependent values.

Closed

#56,799 opened on Apr 3, 2021

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 (13 comments) (0 reactions) (0 assignees)Swift (10,719 forks)batch import
bugc++ interopcompilergood first issue

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Description
Previous ID SR-14443
Radar rdar://problem/83367285
Original Reporter @zoecarver
Type Bug
Votes 0
Component/s Compiler
Labels Bug, CxxInterop, StarterBug
Assignee Rajagopalan (JIRA)
Priority Medium

md5: f34665bb62c6ff5d157cb3bd483d8006

Issue Description:

A while theindigamer (JIRA User) found this compiler crasher and I never got around to fixing it or creating a bug for it.

struct S {};
template <class T>
 struct IsSubtypeSame {
   static constexpr const S value = T();
};

using Invalid = IsSubtypeSame<int>;

Contributor guide

Research direction
The issue is to prevent a compiler crash when handling invalid dependent C++ values, as shown in the reproduction code. Investigate the C++ interop code in the Swift compiler, likely in lib/Sema/CXXInterop.cpp or similar. Review existing comments for potential approaches. The fix should gracefully handle the invalid template argument instead of crashing. Check if there are any linked PRs or discussions that provide further guidance.
Tech stack
swiftcpp
Domain
tooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
Swift compiler basicsC++ template syntaxCompiler error handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40