invalid trunc should throw

[rurban]

errortests/trunc.rn fails with a var (and also a constant)

variable should add a runtime truncation check:

%2 = trunc i64 %1 to i16, !dbg !208
; missing %1 vs %2 check

constant may throw directly at compile-time:

println "%x16" % <u16>0xdeadbeef =>
%1 = trunc i64 3735928559 to i16, !dbg !205

diff --git llvm/genllvm.c llvm/genllvm.c
index a9fff61..245cb0d 100644
--- llvm/genllvm.c
+++ llvm/genllvm.c
@@ -1490,6 +1490,8 @@ static llElement resizeSmallInteger(llElement element, uint32 newWidth, bool isS
   char *operation;
   if (newWidth < oldWidth) {
     operation = "trunc";
+    //TODO if constant throw error if truncation looses info.
+    //     else if not constant add code to check at run-time.
   } else {
     deDatatypeType type = deDatatypeGetType(oldDatatype);
     if (type == DE_TYPE_INT) {

See also: https://cwe.mitre.org/data/definitions/197.html