all: remove unnecessary IError() casts

vlib/io/buffered_reader.v

@@ -38,21 +38,21 @@ pub fn new_buffered_reader(o BufferedReaderConfig) &BufferedReader {
 // read fufills the Reader interface
 pub fn (mut r BufferedReader) read(mut buf []u8) !int {
 	if r.end_of_stream {
-		return IError(Eof{})
+		return Eof{}
 	}
 	// read data out of the buffer if we dont have any
 	if r.needs_fill() {
 		if !r.fill_buffer() {
 			// end of stream
-			return IError(Eof{})
+			return Eof{}
 		}
 	}
 	read := copy(mut buf, r.buf[r.offset..r.len])
 	if read == 0 {
-		return IError(NotExpected{
+		return NotExpected{
 			cause: 'invalid copy of buffer'
 			code: -1
-		})
+		}
 	}
 	r.offset += read
 	return read

vlib/io/custom_string_reading_test.v

@@ -15,7 +15,7 @@ fn (mut s StringReader) read(mut buf []u8) !int {
 		eprintln('>>>> StringReader.read output buf.len: $buf.len')
 	}
 	if s.place > s.text.len + 1 {
-		return IError(io.Eof{})
+		return io.Eof{}
 	}
 	mut howmany := imin(buf.len, s.text.len - s.place)
 	xxx := s.text[s.place..s.place + howmany].bytes()

vlib/io/io_test.v

@@ -14,7 +14,7 @@ pub mut:
 
 fn (mut b Buf) read(mut buf []u8) !int {
 	if !(b.i < b.bytes.len) {
-		return IError(io.Eof{})
+		return io.Eof{}
 	}
 	n := copy(mut buf, b.bytes[b.i..])
 	b.i += n

vlib/io/reader_test.v

@@ -9,7 +9,7 @@ mut:
 
 fn (mut b Buf) read(mut buf []u8) !int {
 	if !(b.i < b.bytes.len) {
-		return IError(Eof{})
+		return Eof{}
 	}
 	n := copy(mut buf, b.bytes[b.i..])
 	b.i += n
@@ -46,7 +46,7 @@ mut:
 
 fn (mut s StringReader) read(mut buf []u8) !int {
 	if s.place >= s.text.len {
-		return IError(Eof{})
+		return Eof{}
 	}
 	read := copy(mut buf, s.text[s.place..].bytes())
 	s.place += read