Expand struct layout options

docs/language.md

@@ -50,6 +50,13 @@ To type a variable as a signed integer N bits wide, use `iN`:
 
 For an unsigned integer, use a `u` prefix instead of `i`.
 
+Type aliases can be used with annotations to create integer types with specific byte orders:
+
+```
+type be16 = u16 @byte_order(BigEndian);
+type le16 = u16 @byte_order(LittleEndian);
+```
+
 ### Floats
 
 Use the type `float` for floating-point numbers.
@@ -170,6 +177,33 @@ Single-element structs do not require a trailing comma:
 let Thing thing = { 1234 };
 ```
 
+#### Structure Layout
+
+To pack a structure in Haven, use the `@layout` annotation:
+
+```
+type Point = struct @layout(packed) {
+    i32 x;
+    i32 y; /* starts at 4th byte of structure - packed layout omits any inter-field padding */
+};
+```
+
+To control the layout of a structure in Haven, use the `@offset` annotation:
+
+```
+type Point = struct {
+    i32 x @offset(8); /* starts at 8th byte of the structure */
+    i32 y @offset(4); /* starts at 4th byte of the structure */
+    i32 z; /* fills the available hole at byte 0 of the structure */
+    i32 w; /* starts at next available slot in the structure, at 12th byte */
+};
+```
+
+Fields that do not have offsets specified will fill available holes in the structure on either side of `@offset`-positioned fields.
+
+Offsets are not permitted to overlap and compile-time analysis will error if an impossible layout is requested.
+Note that adding offsets implies a packed structure layout, even without the annotation.
+
 ### Enums
 
 You may define an enum type using two forms.

src/bin/lsp/semantic_tokens.ml

@@ -205,7 +205,7 @@ let symbol_is_operator = function
   | LtEq | GtEq | LShift | RShift | Lt | Gt | Star | Caret | Plus | Minus
   | Slash | Percent | Equal | Ampersand | Pipe | Bang | Tilde | LParen | RParen
   | LBrace | RBrace | LBracket | RBracket | Comma | Dot | Semicolon | Colon
-  | Underscore ->
+  | Underscore | At ->
       true
 
 let collect_lexical_tokens (parsed : CST.parsed_program) =
@@ -219,10 +219,6 @@ let collect_lexical_tokens (parsed : CST.parsed_program) =
               (loc_of_raw_tok
                  { tok = entry.token; startp = entry.startp; endp = entry.endp })
         | Lexer.Raw.Ident _ -> acc
-        | Lexer.Raw.Directive Assert ->
-            add_token_for_loc acc ~token_type:"keyword"
-              (loc_of_raw_tok
-                 { tok = entry.token; startp = entry.startp; endp = entry.endp })
         | Lexer.Raw.Numeric_type _ | Vec_type _ | Mat_type _ | Vec_hole_type
         | Mat_hole_type | Float_type | Void_type | Str_type ->
             add_token_for_loc acc ~token_type:"type"