Swift Compiler Crash with sharing-grdb 0.5.0 and Swift 6.1.2

[doozMen]

Description

Summary

The Swift compiler crashes with a signal 6 assertion failure when building a project that uses sharing-grdb 0.5.0 with Swift 6.1.2. The crash occurs during the compilation of StructuredQueriesCore's QueryBindable.swift file.

Environment

• Swift Version: 6.1.2-RELEASE
• Xcode Version: Swift toolchain swift-6.1.2-RELEASE.xctoolchain
• Platform: macOS (darwin)
• sharing-grdb Version: 0.5.0
• GRDB Version: 7.5.0 (transitive dependency)

Steps to Reproduce

1. Create a new Swift package with the following Package.swift:

// swift-tools-version: 6.1
import PackageDescription

let package = Package(
    name: "timestory-mcp",
    platforms: [
        .macOS(.v15)
    ],
    dependencies: [
        .package(url: "https://github.com/pointfreeco/sharing-grdb.git", from: "0.5.0"),
    ],
    targets: [
        .executableTarget(
            name: "timestory-mcp",
            dependencies: [
                .product(name: "SharingGRDB", package: "sharing-grdb"),
            ]
        ),
    ]
)

2. Create a model using the @table macro:

import Foundation
import SharingGRDB
import GRDB

@Table("timesheets")
struct Timesheet: Codable, FetchableRecord, PersistableRecord {
    var id: String
    var date: Date
    // ... other properties
}

3. Run swift build

Expected Behavior

The project should compile successfully.

Actual Behavior

The compiler crashes with the following assertion failure:

error: compile command failed due to signal 6 (use -v to see invocation)
Assertion failed: ((path.size() == 1 && path[0].getKind() == ConstraintLocator::SubscriptMember) || (path.size() == 2 && path[1].getKind() == ConstraintLocator::KeyPathDynamicMember)), function addKeyPathApplicationRootConstraint, file CSSimplify.cpp, line 15827.

Crash Details

Stack Trace (Abbreviated)

Stack dump:
0.	Program arguments: /Users/.../swift-6.1.2-RELEASE.xctoolchain/usr/bin/swift-frontend -frontend -c 
    [...]/StructuredQueriesCore/QueryBindable.swift
1.	Swift version 6.1.2-dev
2.	Compiling with effective language version 6.0
3.	While evaluating request TypeCheckSourceFileRequest
4.	While evaluating request TypeCheckFunctionBodyRequest
5.	While type-checking statement
6.	While type-checking expression
7.	While type-checking-target starting at QueryBindable.swift:204:5

Full Error Location

The crash occurs while compiling:

• File: .build/checkouts/swift-structured-queries/Sources/StructuredQueriesCore/QueryBindable.swift
• During primary file compilation of multiple StructuredQueriesCore files

Assertion Details

• File: CSSimplify.cpp
• Line: 15827
• Function: addKeyPathApplicationRootConstraint
• Assertion: Path validation for ConstraintLocator

The error specifically occurs when compiling:

• /Sources/StructuredQueriesCore/PrimaryKeyed.swift
• At line 28-30 during type checking of TableDraft extension

Workaround

Reverting to plain GRDB without sharing-grdb allows the project to compile successfully:

dependencies: [
    .package(url: "https://github.com/groue/GRDB.swift.git", from: "7.0.0"),
],

Additional Context

• The crash appears to be related to the swift-structured-queries dependency that sharing-grdb uses
• The issue occurs specifically with Swift 6.1.2; compatibility with earlier Swift versions has not been tested
• The crash happens during constraint solving in the type checker, suggesting it may be related to complex generic constraints or type inference
• When building with xcodebuild (Xcode 16.4, Build version 16F6), it reports: error: Macro "StructuredQueriesMacros" from package "swift-structured-queries" must be enabled before it can be used

Related Issues

This may be related to other Swift 6.x compatibility issues with complex generic code or macro expansions.

Reproduction

clone https://github.com/pointfreeco/sharing-grdb
run swift test
I uses swiftly with 6.0,1.2 .. all of them and 6.2-snapshot

Expected behavior

xcodebuild has same error but xcode itself can build and run tests 🤯

Environment

swiftly installed 6.1.2 and 6.2-snapshot

Apple Swift version 6.1.2 (swift-6.1.2-RELEASE)
Target: arm64-apple-macosx15.0

Additional information

No response

[woodymelling]

I've been experiencing this with a bunch of libraries including sharing, structured queries and more. They compile fine with the Xcode Toolchain and the compiler crashes out on the macOS toolchain that you would run using swiftly and swift build

It seems like the MacOS toolchain may have assertions enabled on it, where the Xcode toolchain does not.

The last couple changes to the toolchains seem like they could have introduced this issue, as they add a macOS only flag and something to enable assertions.

#79870
#80759
#78693

Here are some related issues that haven't seem to get the traction needed to get answers

[marcprux]

I'll also add that there is an ongoing discussion about whether all the toolchains should harmonize on enabling assertions or not: https://forums.swift.org/t/can-we-get-consistent-assertion-behavior-in-the-latest-release-swift-compiler-across-host-platforms/80545

Adding your experiences to that thread might help garner attention and consideration for the issue.