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Fix crash in merge-modules involving a file with extension of nested type #35809

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13 changes: 11 additions & 2 deletions lib/Serialization/Deserialization.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1241,6 +1241,7 @@ static void filterValues(Type expectedTy, ModuleDecl *expectedModule,
values.erase(newEnd, values.end());
}

/// Look for nested types in all files of \p extensionModule except from the \p thisFile.
static TypeDecl *
findNestedTypeDeclInModule(FileUnit *thisFile, ModuleDecl *extensionModule,
Identifier name, NominalTypeDecl *parent) {
Expand All @@ -1256,6 +1257,13 @@ findNestedTypeDeclInModule(FileUnit *thisFile, ModuleDecl *extensionModule,
return nullptr;
}

/// Look for nested types in all files of \p extensionModule.
static TypeDecl *
findNestedTypeDeclInModule(ModuleDecl *extensionModule,
Identifier name, NominalTypeDecl *parent) {
return findNestedTypeDeclInModule(nullptr, extensionModule, name, parent);
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This makes me nervous since we can now set up a cross-ref that causes resolution to re-enter itself - especially through a name lookup. This was the cause of a ton of circular lookup problems in the SDK when we were refactoring the clang importer. Lazy member loading no longer has re-entrancy guards in it to catch this too...

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Wouldn't a circular issue be detected in the frontend invocations before reaching merge-modules?
But regardless, it looks to me that this particular code-path follows the strict xref path components, so it's going to reach the end of the lookup by definition.

}

Expected<Decl *>
ModuleFile::resolveCrossReference(ModuleID MID, uint32_t pathLen) {
using namespace decls_block;
Expand Down Expand Up @@ -1502,10 +1510,11 @@ ModuleFile::resolveCrossReference(ModuleID MID, uint32_t pathLen) {
extensionModule = baseType->getModuleContext();

// Fault in extensions, then ask every file in the module.
// We include the current file in the search because the cross reference
// may involve a nested type of this file.
(void)baseType->getExtensions();
auto *nestedType =
findNestedTypeDeclInModule(getFile(), extensionModule,
memberName, baseType);
findNestedTypeDeclInModule(extensionModule, memberName, baseType);

// For clang module units, also search tables in the overlays.
if (!nestedType) {
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
public class MyCls {
public static func doIt(_: Inner1.Inner2) {}

public struct Inner1 {}
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
public extension MyCls.Inner1 {
struct Inner2 {}
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
{
"./f1.swift": {
"swift-dependencies": "./f1.swiftdeps",
"swiftmodule": "./f1~partial.swiftmodule"
},
"./f2.swift": {
"swift-dependencies": "./f2.swiftdeps",
"swiftmodule": "./f2~partial.swiftmodule"
},
"": {
"swift-dependencies": "./main~buildrecord.swiftdeps"
}
}
9 changes: 9 additions & 0 deletions validation-test/Serialization/crash-nested-extension.swift
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
// RUN: %empty-directory(%t)
// RUN: cp -r %S/Inputs/crash-nested-extension/* %t
// RUN: cd %t
// RUN: %swiftc_driver -output-file-map %t/output.json -incremental ./f1.swift ./f2.swift -module-name MyMod -j1 -disable-batch-mode -emit-module -emit-module-path MyMod.swiftmodule -v

// RUN: %empty-directory(%t)
// RUN: cp -r %S/Inputs/crash-nested-extension/* %t
// RUN: cd %t
// RUN: %swiftc_driver -output-file-map %t/output.json -incremental -Xfrontend -experimental-skip-all-function-bodies -Xfrontend -experimental-allow-module-with-compiler-errors ./f1.swift ./f2.swift -module-name MyMod -j1 -disable-batch-mode -emit-module -emit-module-path MyMod.swiftmodule -v