Crash with protected constructor and generic intermediate class

[zsilbi]

Error:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x100 pc=0x7917cb]

goroutine 85 [running]:
github.com/microsoft/typescript-go/internal/checker.(*Checker).getBaseTypes(0xc001035908, 0xc000f8a9a0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:18245 +0x2b
github.com/microsoft/typescript-go/internal/checker.(*Checker).typeHasProtectedAccessibleBase(0xc001035908, 0xc00019e8c0, 0xc0001da05f?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:8363 +0x25
github.com/microsoft/typescript-go/internal/checker.(*Checker).typeHasProtectedAccessibleBase(0xc001035908, 0xc00019e8c0, 0xc000f1b8e8?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:8389 +0xc5
github.com/microsoft/typescript-go/internal/checker.(*Checker).isConstructorAccessible(0xc001035908, 0xc000150af0, 0x1?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:8347 +0x225
github.com/microsoft/typescript-go/internal/checker.(*Checker).resolveNewExpression(0xc001035908, 0xc000150af0, 0x0, 0x0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:8287 +0x145
github.com/microsoft/typescript-go/internal/checker.(*Checker).resolveSignature(0xc001035f18?, 0xd10b60?, 0xc000150af0?, 0x7fbe4e?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:8143 +0x3a
github.com/microsoft/typescript-go/internal/checker.(*Checker).getResolvedSignature(0xc001035908, 0xc000150af0, 0x0, 0x0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:8113 +0xd8
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkCallExpression(0xc001035908, 0xc000150af0, 0x0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:8008 +0x4f
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkExpressionWorker(0xc001035908, 0x7f5890?, 0x1035908?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:7392 +0x325
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkExpressionEx(0xc001035908, 0xc000150af0, 0x0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:7178 +0x52
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkExpression(...)
        github.com/microsoft/typescript-go/internal/checker/checker.go:7171
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkExpressionStatement(0xc001035908, 0xc000173900)
        github.com/microsoft/typescript-go/internal/checker/checker.go:6951 +0x46
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElementWorker(0xc001035908, 0xc000173900)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2231 +0x29e
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElement(0xc001035908, 0x0?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2157 +0x4e
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElements(0xc001035908, {0xc0001349c8, 0x1, 0x598da7?})
        github.com/microsoft/typescript-go/internal/checker/checker.go:2148 +0x2d
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkBlock(0xc001035908, 0xc0001dc060)
        github.com/microsoft/typescript-go/internal/checker/checker.go:3590 +0xfc
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElementWorker(0xc001035908, 0xc0001dc060)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2227 +0x365
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElement(0xc001035908, 0xc0004eb0e8?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2157 +0x4e
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkFunctionOrMethodDeclaration(0xc001035908, 0xc0001252c0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:3258 +0x131
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkMethodDeclaration(0xc001035908, 0xc0001252c0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2623 +0x11b
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElementWorker(0xc001035908, 0xc0001252c0)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2183 +0xd9
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElement(0xc001035908, 0x46fc59?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2157 +0x4e
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElements(0xc001035908, {0xc0001349d0, 0x1, 0xc001035908?})
        github.com/microsoft/typescript-go/internal/checker/checker.go:2148 +0x2d
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkClassDeclaration(0xc001035908, 0xc00019c360)
        github.com/microsoft/typescript-go/internal/checker/checker.go:4075 +0x133
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElementWorker(0xc001035908, 0xc00019c360)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2263 +0x347
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElement(0xc001035908, 0xc0016044b0?)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2157 +0x4e
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceElements(0xc001035908, {0xc0001349d8, 0x3, 0xc00002cb10?})
        github.com/microsoft/typescript-go/internal/checker/checker.go:2148 +0x2d
github.com/microsoft/typescript-go/internal/checker.(*Checker).checkSourceFile(0xc001035908, {0xd0b760, 0x126a380}, 0xc0001818c8)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2120 +0x11c
github.com/microsoft/typescript-go/internal/checker.(*Checker).CheckSourceFile(0xc001035908, {0xd0b760, 0x126a380}, 0xc0001818c8)
        github.com/microsoft/typescript-go/internal/checker/checker.go:2109 +0x5c
github.com/microsoft/typescript-go/internal/compiler.(*Program).CheckSourceFiles.func1-range1(0x1?)
        github.com/microsoft/typescript-go/internal/compiler/program.go:273 +0x3e
github.com/microsoft/typescript-go/internal/compiler.(*checkerPool).Files.func1(0xc001604480)
        github.com/microsoft/typescript-go/internal/compiler/checkerpool.go:82 +0x88
github.com/microsoft/typescript-go/internal/compiler.(*Program).CheckSourceFiles.func1()
        github.com/microsoft/typescript-go/internal/compiler/program.go:272 +0xdb
github.com/microsoft/typescript-go/internal/core.(*parallelWorkGroup).Queue.func1()
        github.com/microsoft/typescript-go/internal/core/workgroup.go:39 +0x50
created by github.com/microsoft/typescript-go/internal/core.(*parallelWorkGroup).Queue in goroutine 1
        github.com/microsoft/typescript-go/internal/core/workgroup.go:37 +0x85

Reproduction:

class C {
  protected constructor() {}
}

class B<T = any> extends C {}

class A extends B {
  f() {
    new A();
  }
}

Repository: https://github.com/zsilbi/tsgo-repro

[jakebailey]

This one's pretty funky. #1296 did correctly find the crashing code and "fix" the bug, but there's a deeper problem here that actually exists in the old codebase too. getBaseTypes (and many class-based functions related to it) says it only accepts InterfaceType. Yet, we call the functions on TypeReference and AnonymousType, which then drops a bunch of random props on the wrong types.

It's possible that #1296 is sufficient to fix the problem, since it's not clear to me that getBaseTypes would even have worked. But, maybe we should just fix the issue in general and make these functions work on the other types?

In the old code, I probably would have just unioned up the types and added the missing props, but in the new code, we can't just drop random props onto things. We could move this info to ObjectType, but that would increase the size of all of the ObjectTypes instances when it's only a couple of them.

@ahejlsberg curious what you think on this one.

An easy way to check these out in Strada is to drop this at the top of getBaseTypes:

Debug.assert(getObjectFlags(type) & ObjectFlags.ClassOrInterface, "type must be class or interface, got " + Debug.formatObjectFlags(getObjectFlags(type)));