extern for aliased template instantiation

[dlangBugzillaToGithub]

a11e99z reported this on 2019-08-22T15:08:26Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=20153

Description

I want to export non-mangled instantiated through alias template function.
it can be useful for WASM, DLLs/SharedLibs and etc.
but alias for template instatiation is ignored.
pragma mangle to alias is ignored too.

-----------------------------------
void main() {}

export:                  // EXPORTed
extern (C):              // NO MANGLE but IGNORED
public:

void fun( Char )( Char* ) { }

pragma (mangle, "func")  // IGNORED
alias func = fun!char;
pragma( msg, func.mangleof );

pragma (mangle, "funw")  // IGNORED
alias funw = fun!wchar;
pragma( msg, funw.mangleof );

------------ OUTPUT -----------------------
_D9onlineapp__T3funTaZQhUNaNbNiNfPaZv
_D9onlineapp__T3funTuZQhUNaNbNiNfPuZv


current workaround: wrap template funcs to non-template.

possible solution:
if "alias" locates in non-mangle block (extern(C) for example) then do not mangle name and check that no others entities with same name exists in current context.
OR/AND
make "pragma mangle" working for alias-es too.