Bug 19520 – assert(TypeExp is TypeExp): compiles with empty structs

https://github.com/dlang/dmd/pull/8945 introduced a funny little test. --- struct Foo { alias MyInt = int; } assert(attribs[0] is Foo); // TypeExp is TypeExp. --- This errors in gdc's codegen, because we build the back-end expression before checking the type, but it succeeds with dmd because it checks the type and doesn't evaluate the expression as it's empty. We can easily break dmd though... --- struct Empty { } struct WithSym { int i; } void test() { // error: cannot interpret Empty at compile time static assert(Empty is Empty); // error: cannot interpret WithSym at compile time static assert(WithSym is WithSym); // This compiles !!! assert(Empty is Empty); // error: type WithSym is not an expression assert(WithSym is WithSym); } --- It's quite clear that either all should succeed, or the third test should fail. I don't think its outside the scope of CTFE to evaluate `assert(type is type)` as either true or false, so that should be addressed.

> I don't think its outside the scope of CTFE to evaluate `assert(type is type)` as either true or false, so that should be addressed. Actually, I change my mind, it should be an error.

Commits pushed to master at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/a7a3ee088d0dd5f4d47141ea00edf3d900ecbe46 Fix Issue 19520 - assert(TypeExp is TypeExp): compiles with empty structs https://github.com/dlang/dmd/commit/7b6a0f1254f0e0102afcf6c3b7e4c8699bbfd2b3 Merge pull request #9153 from ibuclaw/issue19520 Fix Issue 19520 - assert(TypeExp is TypeExp): compiles with empty structs