Added safe implicit conversion of uint8 to int16..int64, uint16 to int32..int64 etc.

Added two new tests for unsigned conversions and comparisons between signed numbers.

tests/misc/tunsignedcomp.nim

@@ -0,0 +1,134 @@
+discard """
+  output: ''''''
+"""
+
+# All operations involving uint64 are commented out
+# as they're not yet supported.
+# All other operations are handled by implicit conversions from uints to ints
+# uint64 could be supported but would need special implementation of the operators
+
+# unsigned < signed
+assert 10'u8 < 20'i8
+assert 10'u8 < 20'i16
+assert 10'u8 < 20'i32
+assert 10'u8 < 20'i64
+
+assert 10'u16 < 20'i8
+assert 10'u16 < 20'i16
+assert 10'u16 < 20'i32
+assert 10'u16 < 20'i64
+
+assert 10'u32 < 20'i8
+assert 10'u32 < 20'i16
+assert 10'u32 < 20'i32
+assert 10'u32 < 20'i64
+
+# assert 10'u64 < 20'i8
+# assert 10'u64 < 20'i16
+# assert 10'u64 < 20'i32
+# assert 10'u64 < 20'i64
+
+# signed < unsigned
+assert 10'i8 < 20'u8
+assert 10'i8 < 20'u16
+assert 10'i8 < 20'u32
+# assert 10'i8 < 20'u64
+
+assert 10'i16 < 20'u8
+assert 10'i16 < 20'u16
+assert 10'i16 < 20'u32
+# assert 10'i16 < 20'u64
+
+assert 10'i32 < 20'u8
+assert 10'i32 < 20'u16
+assert 10'i32 < 20'u32
+# assert 10'i32 < 20'u64
+
+assert 10'i64 < 20'u8
+assert 10'i64 < 20'u16
+assert 10'i64 < 20'u32
+# assert 10'i64 < 20'u64
+
+# unsigned <= signed
+assert 10'u8 <= 20'i8
+assert 10'u8 <= 20'i16
+assert 10'u8 <= 20'i32
+assert 10'u8 <= 20'i64
+
+assert 10'u16 <= 20'i8
+assert 10'u16 <= 20'i16
+assert 10'u16 <= 20'i32
+assert 10'u16 <= 20'i64
+
+assert 10'u32 <= 20'i8
+assert 10'u32 <= 20'i16
+assert 10'u32 <= 20'i32
+assert 10'u32 <= 20'i64
+
+# assert 10'u64 <= 20'i8
+# assert 10'u64 <= 20'i16
+# assert 10'u64 <= 20'i32
+# assert 10'u64 <= 20'i64
+
+# signed <= unsigned
+assert 10'i8 <= 20'u8
+assert 10'i8 <= 20'u16
+assert 10'i8 <= 20'u32
+# assert 10'i8 <= 20'u64
+
+assert 10'i16 <= 20'u8
+assert 10'i16 <= 20'u16
+assert 10'i16 <= 20'u32
+# assert 10'i16 <= 20'u64
+
+assert 10'i32 <= 20'u8
+assert 10'i32 <= 20'u16
+assert 10'i32 <= 20'u32
+# assert 10'i32 <= 20'u64
+
+assert 10'i64 <= 20'u8
+assert 10'i64 <= 20'u16
+assert 10'i64 <= 20'u32
+# assert 10'i64 <= 20'u64
+
+# signed == unsigned
+assert 10'i8 == 10'u8
+assert 10'i8 == 10'u16
+assert 10'i8 == 10'u32
+# assert 10'i8 == 10'u64
+
+assert 10'i16 == 10'u8
+assert 10'i16 == 10'u16
+assert 10'i16 == 10'u32
+# assert 10'i16 == 10'u64
+
+assert 10'i32 == 10'u8
+assert 10'i32 == 10'u16
+assert 10'i32 == 10'u32
+# assert 10'i32 == 10'u64
+
+assert 10'i64 == 10'u8
+assert 10'i64 == 10'u16
+assert 10'i64 == 10'u32
+# assert 10'i64 == 10'u64
+
+# unsigned == signed
+assert 10'u8 == 10'i8
+assert 10'u8 == 10'i16
+assert 10'u8 == 10'i32
+# assert 10'u8 == 10'i64
+
+assert 10'u16 == 10'i8
+assert 10'u16 == 10'i16
+assert 10'u16 == 10'i32
+# assert 10'u16 == 10'i64
+
+assert 10'u32 == 10'i8
+assert 10'u32 == 10'i16
+assert 10'u32 == 10'i32
+# assert 10'u32 == 10'i64
+
+# assert 10'u64 == 10'i8
+# assert 10'u64 == 10'i16
+# assert 10'u64 == 10'i32
+# assert 10'u64 == 10'i64