feat: error message for unknown global variables

src/Ir.zig

@@ -166,16 +166,24 @@ pub const Inst = struct {
         declaration,
         decl_knot,
         decl_var,
+        /// Uses the `str_tok` union field.
         decl_ref,
         alloc,
         load,
         store,
+        /// Uses the `bin` union field.
         add,
+        /// Uses the `bin` union field.
         sub,
+        /// Uses the `bin` union field.
         mul,
+        /// Uses the `bin` union field.
         div,
+        /// Uses the `bin` union field.
         mod,
+        /// Uses the `un` union field.
         neg,
+        /// Uses the `un` union field.
         not,
         cmp_eq,
         cmp_neq,
@@ -183,8 +191,10 @@ pub const Inst = struct {
         cmp_gte,
         cmp_lt,
         cmp_lte,
-        integer,
-        string,
+        /// Uses the `int` union field.
+        int,
+        /// Uses the `str` union field.
+        str,
         block,
         condbr,
         @"break",
@@ -212,17 +222,22 @@ pub const Inst = struct {
             lhs: Ref,
             rhs: Ref,
         },
-        integer: struct {
-            value: u64,
-        },
-        string: struct {
+        int: u64,
+        str: struct {
             /// Offset into `string_bytes`.
             start: NullTerminatedString,
+            /// Number of bytes in the string.
+            len: u32,
 
-            pub fn get(self: @This(), ir: Ir) []const u8 {
-                return nullTerminatedString(ir, self.start);
+            pub fn get(self: @This(), code: Ir) []const u8 {
+                return code.string_bytes[@intFromEnum(self.start)..][0..self.len];
             }
         },
+        str_tok: struct {
+            /// Offset into `string_bytes`.
+            start: NullTerminatedString,
+            src_offset: u32,
+        },
     };
 
     pub const Declaration = struct {