String Switch Lowering

[timotheecour]

On Saturday, 27 January 2018 at 10:38:46 UTC, Kagamin wrote:
> dmd

see also this horrendous stacktrace when calling getopt with a 
bad argument:

full stacktrace:

https://gist.github.com/timotheecour/d6b623bd3d223f5d958cd86adffd7807

just 1 line of this stacktrace:

```
28  dscanner                            0x000000010d59f428 @safe 
void std.getopt.getoptImpl!(std.getopt.config, immutable(char)[], 
bool*, immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], immutable(char)[]*, immutable(char)[], 
immutable(char)[]*, immutable(char)[], bool*, immutable(char)[], 
immutable(char)[][]*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*).getoptImpl(ref immutable(char)[][], ref 
std.getopt.configuration, ref std.getopt.GetoptResult, ref 
std.getopt.GetOptException, void[][immutable(char)[]], 
void[][immutable(char)[]], std.getopt.config, immutable(char)[], 
bool*, immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], immutable(char)[]*, immutable(char)[], 
immutable(char)[]*, immutable(char)[], bool*, immutable(char)[], 
immutable(char)[][]*, immutable(char)[], bool*, 
immutable(char)[], bool*, immutable(char)[], bool*, 
immutable(char)[], bool*) + 460
```

https://dlang.org/blog/2017/12/20/ds-newfangled-name-mangling/ 
doesn't seem to help in cases like that