Add the Decode module

crates/compiler/builtins/roc/Decode.roc

@@ -0,0 +1,77 @@
+interface Decode
+    exposes [
+        DecodeError,
+        DecodeResult,
+        Decoder,
+        Decoding,
+        DecoderFormatting,
+        decoder,
+        u8,
+        u16,
+        u32,
+        u64,
+        u128,
+        i8,
+        i16,
+        i32,
+        i64,
+        i128,
+        f32,
+        f64,
+        dec,
+        bool,
+        string,
+        list,
+        custom,
+        decodeWith,
+        fromBytesPartial,
+        fromBytes,
+    ]
+    imports []
+
+DecodeError : [TooShort]
+
+DecodeResult val : { result : Result val DecodeError, rest : List U8 }
+
+Decoder val fmt := List U8, fmt -> DecodeResult val | fmt has DecoderFormatting
+
+Decoding has
+    decoder : Decoder val fmt | val has Decoding, fmt has DecoderFormatting
+
+DecoderFormatting has
+    u8 : Decoder U8 fmt | fmt has DecoderFormatting
+    u16 : Decoder U16 fmt | fmt has DecoderFormatting
+    u32 : Decoder U32 fmt | fmt has DecoderFormatting
+    u64 : Decoder U64 fmt | fmt has DecoderFormatting
+    u128 : Decoder U128 fmt | fmt has DecoderFormatting
+    i8 : Decoder I8 fmt | fmt has DecoderFormatting
+    i16 : Decoder I16 fmt | fmt has DecoderFormatting
+    i32 : Decoder I32 fmt | fmt has DecoderFormatting
+    i64 : Decoder I64 fmt | fmt has DecoderFormatting
+    i128 : Decoder I128 fmt | fmt has DecoderFormatting
+    f32 : Decoder F32 fmt | fmt has DecoderFormatting
+    f64 : Decoder F64 fmt | fmt has DecoderFormatting
+    dec : Decoder Dec fmt | fmt has DecoderFormatting
+    bool : Decoder Bool fmt | fmt has DecoderFormatting
+    string : Decoder Str fmt | fmt has DecoderFormatting
+    list : Decoder elem fmt -> Decoder (List elem) fmt | fmt has DecoderFormatting
+
+custom : (List U8, fmt -> DecodeResult val) -> Decoder val fmt | fmt has DecoderFormatting
+custom = \decode -> @Decoder decode
+
+decodeWith : List U8, Decoder val fmt, fmt -> DecodeResult val | fmt has DecoderFormatting
+decodeWith = \bytes, @Decoder decode, fmt -> decode bytes fmt
+
+fromBytesPartial : List U8, fmt -> DecodeResult val | val has Decoding, fmt has DecoderFormatting
+fromBytesPartial = \bytes, fmt -> decodeWith bytes decoder fmt
+
+fromBytes : List U8, fmt -> Result val [Leftover (List U8)]DecodeError | val has Decoding, fmt has DecoderFormatting
+fromBytes = \bytes, fmt ->
+    { result, rest } = fromBytesPartial bytes fmt
+
+    if List.isEmpty rest then
+        when result is
+            Ok val -> Ok val
+            Err TooShort -> Err TooShort
+    else
+        Err (Leftover rest)