Bug 4366 – ICE(mtype.c) constrained template pure function with array/pointer parameter

DMD aborts with assertion failure in Type::check() if a constrained templated pure function has a named parameter of array or pointer type. Compiling the following causes dmd to abort (2.045 and r556): -------------------- void foo(T)(T a, T[] b) pure if (1) { } alias foo!(int) K; -------------------- % dmd -o- -c test Assertion failed: (tn->mod & MODimmutable || tn->mod & MODconst), function check, file mtype.c, line 871. -------------------- GDB backtrace: ... #3 0x283a2ef6 in __assert () from /lib/libc.so.7 #4 0x080fa0fe in Type::check () #5 0x080fa23f in Type::fixTo () #6 0x081001b7 in Type::constOf () #7 0x08136150 in TemplateDeclaration::makeParamNamesVisibleInConstraint () #8 0x08136415 in TemplateDeclaration::matchWithInstance () #9 0x08138cac in TemplateInstance::findBestMatch () #10 0x08139c67 in TemplateInstance::semantic () #11 0x0813a190 in TemplateInstance::semantic () #12 0x081005d3 in TypeInstance::resolve () ... The assertion does not fail in the following cases: -------------------- void bar(T)(T a, T[] b) pure { } // no constraint void dee(T)(T a, T[] ) pure if (1) { } // array parameter is unnamed void mew(T)(T a, T[] b) if (1) { } // impure alias bar!(int) L; // okay alias dee!(int) M; // okay alias mew!(int) N; // okay --------------------

The ICE occurs during the call in these lines in template.c, makeParamNamesVisibleInConstraint(). if (fd->type && fd->isPure()) vtype = vtype->addMod(MODconst); Removing those lines allows the code to compile, and the DMD test suite still passes. So why are they there? I wrote the makeParamNamesVisibleInConstraint() function, but I just copied those lines from func.c, where interestingly they don't cause any problems. Still need to work out what the difference is.

*** This issue has been marked as a duplicate of issue 4434 ***