compiler: fix int casting to use the source signedness

Previously, when casting an integer to a bigger integer, the destination
signedness was used. This is problematic when casting a negative int16
to uint32, for example, because it would cause zero-extension.

compiler/compiler.go

@@ -2559,7 +2559,7 @@ func (c *Compiler) parseConvert(typeFrom, typeTo types.Type, value llvm.Value, p
 			// Conversion between two integers.
 			if sizeFrom > sizeTo {
 				return c.builder.CreateTrunc(value, llvmTypeTo, ""), nil
-			} else if typeTo.Info()&types.IsUnsigned != 0 { // if unsigned
+			} else if typeFrom.Info()&types.IsUnsigned != 0 { // if unsigned
 				return c.builder.CreateZExt(value, llvmTypeTo, ""), nil
 			} else { // if signed
 				return c.builder.CreateSExt(value, llvmTypeTo, ""), nil

src/runtime/print.go

@@ -39,7 +39,7 @@ func printuint16(n uint16) {
 	printuint32(uint32(n))
 }
 
-func printint16(n uint16) {
+func printint16(n int16) {
 	printint32(int32(n))
 }