[Issue 20153] New: extern for aliased template instantiation

[d-bugmail at puremagic.com]

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

          Issue ID: 20153
           Summary: extern for aliased template instantiation
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: black80 at bk.ru

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.

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