diff --git a/lang/src/ast.asm b/lang/src/ast.asm
index 0015bc1..b8974f7 100644
--- a/lang/src/ast.asm
+++ b/lang/src/ast.asm
@@ -82,6 +82,7 @@ global ast_walk_for_each
 ;;   kind: u8,
 ;;   data: *const (),
 ;;   extra: usize,
+;;   span: u64,
 ;; }
 ;;
 ;; struct AstArgument {
@@ -101,6 +102,7 @@ global ast_walk_for_each
 parse_func:
     push rbp
     mov rbp, rsp
+    sub rsp, 8                  ; span
     push rdi
 
     ; start-structs
@@ -114,17 +116,21 @@ parse_func:
     ; }
     ; end-structs
 
-    sub rsp, 56
-    ; name: *const u8 [0..8]
-    ; name_len: usize [8..16]
-    ; args_ptr: *const u64 [16..24]
-    ; args_len: usize [24..32]
-    ; return_type: Type [32..48]
-    ; body: u64 [48..56]
+    ; span: u64 [64..72]
     ; ast: *mut Ast [56..64]
+    ; body: u64 [48..56]
+    ; return_type: Type [32..48]
+    ; args_len: usize [24..32]
+    ; args_ptr: *const u64 [16..24]
+    ; name_len: usize [8..16]
+    ; name: *const u8 [0..8]
+    sub rsp, 56
     mov qword [rsp + 16], 8         ; <*u64>::dangling()
     mov qword [rsp + 24], 0         ; args_len
 
+    call tokeniser_get_cursor
+    mov [rsp + 64], rax             ; span
+
     mov dil, TOKEN_FN
     call unwrap_token
     mov dil, TOKEN_IDENT
@@ -161,9 +167,11 @@ parse_func:
     mov rdx, 56                 ; size_of::<AstFunction>
     call memcpy
 
-    mov byte [rsp], AST_FUNCTION    ; kind
-    mov [rsp + 8], rdi              ; data
-    mov qword [rsp + 16], 0         ; extra
+    mov byte [rsp], AST_FUNCTION    ; AstNode.kind
+    mov [rsp + 8], rdi              ; AstNode.data
+    mov qword [rsp + 16], 0         ; AstNode.extra
+    mov rdi, [rsp + 64]             ; span
+    mov [rsp + 24], rdi             ; AstNode.span
     mov rdi, [rsp + 56]             ; Ast
     lea rsi, [rsp]                  ; &AstNode
     call vec_push
@@ -172,6 +180,7 @@ parse_func:
     dec rax
     add rsp, 56
     pop rdi
+    add rsp, 8
     pop rbp
     ret
     
@@ -189,6 +198,7 @@ parse_func:
 parse_args:
     push rbp
     mov rbp, rsp
+    ; span: u64 [80..88]
     ; vec:      [40..80]
     ; argument: AstArgument { [8..40]
     ;   name: *const u8 [8..16]
@@ -196,7 +206,7 @@ parse_args:
     ;   arg_type: Type [24..40]
     ; }
     ; ast       [0..8]
-    sub rsp, 80
+    sub rsp, 88
     mov [rsp], rdi              ; Ast
 
     lea rdi, [rsp + 40]         ; vec
@@ -210,6 +220,10 @@ parse_args:
     call expect_token
     test rax, rax
     jnz .done_args
+
+    call tokeniser_get_cursor
+    mov [rsp + 80], rax         ; span
+
     mov dil, TOKEN_IDENT
     call unwrap_token
     mov [rsp + 8], rax          ; AstArgument.name
@@ -232,6 +246,8 @@ parse_args:
     mov qword [rsp + 8], AST_ARG      ; AstNode.kind
     mov [rsp + 16], rdi               ; AstNode.data
     mov qword [rsp + 24], 0           ; AstNode.extra
+    mov rdi, [rsp + 80]               ; span
+    mov [rsp + 32], rdi               ; AstNode.span
 
     mov rdi, [rsp]              ; Ast
     lea rsi, [rsp + 8]          ; &AstNode
@@ -256,7 +272,7 @@ parse_args:
 .done_args:
     mov rax, [rsp + 40]   ; args_ptr
     mov rdx, [rsp + 48]   ; args_len
-    add rsp, 80
+    add rsp, 88
     pop rbp
     ret
 
@@ -317,7 +333,7 @@ parse_number:
 parse_primary_expr:
     push rbp
     mov rbp, rsp
-    sub rsp, 32
+    sub rsp, 40
     mov [rsp], rdi         ; Ast
 
     ; start-structs
@@ -328,6 +344,9 @@ parse_primary_expr:
     ; }
     ; end-structs
 
+    call tokeniser_get_cursor
+    mov [rsp + 32], rax         ; span
+
     mov dil, TOKEN_NUMBER
     call expect_token
     test rax, rax
@@ -357,6 +376,7 @@ parse_primary_expr:
     mov qword [rsp + 8], AST_VAR_REF ; AstNode.kind
     mov [rsp + 16], rdi              ; AstNode.data
     mov qword [rsp + 24], 0          ; AstNode.extra
+    ; mov [rsp + 32], span           ; AstNode.span
     mov rdi, [rsp]                   ; Ast
     lea rsi, [rsp + 8]               ; &AstNode
     call vec_push
@@ -370,9 +390,10 @@ parse_primary_expr:
     mov rsi, rdx         ; lexeme len
     call parse_number
     mov rdi, [rsp]                 ; Ast
-    mov byte [rsp + 8], AST_NUMBER ; kind
-    mov [rsp + 16], rax            ; data
-    mov qword [rsp + 24], 0        ; extra
+    mov byte [rsp + 8], AST_NUMBER ; AstNode.kind
+    mov [rsp + 16], rax            ; AstNode.data
+    mov qword [rsp + 24], 0        ; AstNode.extra
+    ; mov [rsp + 32], [rsp + 32]   ; AstNode.span
     lea rsi, [rsp + 8]             ; &AstNode
     call vec_push
     mov rdi, [rsp]              ; Ast
@@ -388,7 +409,7 @@ parse_primary_expr:
     call unwrap_token
     mov rax, [rsp + 8]          ; expr
 .epilogue:
-    add rsp, 32
+    add rsp, 40
     pop rbp
     ret
 .panic:
@@ -412,6 +433,8 @@ parse_binary_expr:
     ; end-structs
 
     sub rsp, 64
+    ; span: u64 [56..64]
+    ; AstNode [32..64]
     ; lexeme: Lexeme [32..56]
     ; right: u64 [24..32]
     ; right_placeness: u8 [20..21]
@@ -426,8 +449,11 @@ parse_binary_expr:
     mov byte [rsp + 17], sil ; upper_precedence
     mov byte [rsp + 16], 0
 
+    call tokeniser_get_cursor
+    mov [rsp + 56], rax         ; span
+
     call parse_prefix_expr
-    mov [rsp + 8], rax           ; left
+    mov [rsp + 8], rax          ; left
     mov [rsp + 19], dl          ; left_placeness
 
 .loop:
@@ -510,6 +536,7 @@ parse_binary_expr:
     mov byte [rsp + 32], AST_BINARY_OP ; AstNode.kind
     mov [rsp + 40], rax                ; AstNode.data
     mov qword [rsp + 48], 0            ; AstNode.extra
+    ; mov [rsp + 56], [rsp + 56]       ; AstNode.span
     mov rdi, [rsp]                  ; Ast
     lea rsi, [rsp + 32]             ; &AstNode
     call vec_push
@@ -547,10 +574,13 @@ parse_statement:
     push rbp
     mov rbp, rsp
 
-    ; Ast     [24..32]
-    ; AstNode [0..24]
-    sub rsp, 32
-    mov [rsp + 24], rdi         ; Ast
+    ; AstNode [8..40]
+    ; Ast [0..8]
+    sub rsp, 40
+    mov [rsp], rdi              ; Ast
+
+    call tokeniser_get_cursor
+    mov [rsp + 32], rax         ; AstNode.span
 
     mov dil, TOKEN_RETURN
     call expect_token
@@ -563,21 +593,21 @@ parse_statement:
     jmp .panic
 
 .let:
-    mov rdi, [rsp + 24]         ; Ast
+    mov rdi, [rsp]              ; Ast
     call ast_parse_let
     mov [rsp], rax              ; statement
     jmp .semi
 
 .return:
-    mov rdi, [rsp + 24]         ; Ast
+    mov rdi, [rsp]              ; Ast
     call parse_expr
-    mov byte [rsp], AST_RETURN_STATEMENT ; kind
-    mov [rsp + 8], rax                   ; data
-    mov qword [rsp + 16], 0              ; extra
-    mov rdi, [rsp + 24]                  ; Ast
-    lea rsi, [rsp]                       ; &AstNode
+    mov byte [rsp + 8], AST_RETURN_STATEMENT ; AstNode.kind
+    mov [rsp + 16], rax                      ; AstNode.data
+    mov qword [rsp + 24], 0                  ; AstNode.extra
+    mov rdi, [rsp]                           ; Ast
+    lea rsi, [rsp]                           ; &AstNode
     call vec_push
-    mov rdi, [rsp + 24]         ; Ast
+    mov rdi, [rsp]              ; Ast
     mov rax, [rdi + 8]          ; Ast.nodes.len()
     dec rax
     mov [rsp], rax
@@ -586,7 +616,7 @@ parse_statement:
     mov dil, TOKEN_SEMI
     call unwrap_token
     mov rax, [rsp]              ; expression
-    add rsp, 32
+    add rsp, 40
     pop rbp
     ret
 .panic:
@@ -598,12 +628,16 @@ parse_block:
     push rbp
     mov rbp, rsp
 
+    ; span: u64             [64..72]
     ; Ast: *mut Ast              [56..64]
     ; statements: Vec<Statement> [8..56]
     ; statement: u64             [0..8]
-    sub rsp, 64
+    sub rsp, 72
     mov [rsp + 56], rdi         ; Ast
 
+    call tokeniser_get_cursor
+    mov [rsp + 64], rax         ; span
+
     mov dil, TOKEN_LBRACE
     call unwrap_token
 
@@ -632,13 +666,15 @@ parse_block:
     jmp .loop
 .done:
     mov rdi, [rsp + 56]         ; Ast
-    mov qword [rsp], AST_BLOCK  ; kind
+    mov qword [rsp], AST_BLOCK  ; AstNode.kind
+    mov rsi, [rsp + 64]         ; span
+    mov [rsp + 24], rsi         ; AstNode.span
     lea rsi, [rsp]              ; &AstNode
     call vec_push
     mov rdi, [rsp + 56]         ; Ast
-    mov rax, [rdi + 8]         ; Ast.nodes.len()
+    mov rax, [rdi + 8]          ; Ast.nodes.len()
     dec rax
-    add rsp, 64
+    add rsp, 72
     pop rbp
     ret
     
@@ -707,11 +743,14 @@ parse_prefix_expr:
     push rbp
     mov rbp, rsp
 
+    ; AstNode [8..40]
     ; ast [0..8]
-    sub rsp, 32
-
+    sub rsp, 40
     mov [rsp], rdi              ; Ast
 
+    call tokeniser_get_cursor
+    mov [rsp + 32], rax         ; AstNode.span
+
     mov dil, TOKEN_STAR
     call expect_token
     test rax, rax
@@ -751,10 +790,10 @@ parse_prefix_expr:
     ; mov rdx, rdx              ; placeness
     call ast_value_to_place
     mov qword [rsp + 8], AST_ADDRESS_OF ; AstNode.kind
-    mov [rsp + 16], rax                ; AstNode.data
-    mov qword [rsp + 24], 0            ; AstNode.extra
-    mov rdi, [rsp]                     ; Ast
-    lea rsi, [rsp + 8]                 ; &AstNode
+    mov [rsp + 16], rax                 ; AstNode.data
+    mov qword [rsp + 24], 0             ; AstNode.extra
+    mov rdi, [rsp]                      ; Ast
+    lea rsi, [rsp + 8]                  ; &AstNode
     call vec_push
     mov rdi, [rsp]              ; Ast
     mov rax, [rdi + 8]          ; Ast.nodes.len()
@@ -763,7 +802,7 @@ parse_prefix_expr:
     jmp .done
 
 .done:
-    add rsp, 32
+    add rsp, 40
     pop rbp
     ret
 
@@ -773,13 +812,17 @@ parse_assignment_expr:
     push rbp
     mov rbp, rsp
 
+    ; span: u64 [32..40]
     ; source [24..32]
     ; dest [16..24]
     ; dest_placeness [8..9]
     ; ast [0..8]
-    sub rsp, 32
+    sub rsp, 40
     mov [rsp], rdi              ; Ast
 
+    call tokeniser_get_cursor
+    mov [rsp + 32], rax         ; span
+
     mov rdi, [rsp]              ; Ast
     call parse_binary_expr
     mov [rsp + 16], rax         ; dest
@@ -796,7 +839,7 @@ parse_assignment_expr:
     mov rsi, [rsp + 16]         ; dest
     movzx rdx, byte [rsp + 8]   ; placeness
     call ast_value_to_place
-    mov [rsp + 16], rax         ; source
+    mov [rsp + 16], rax         ; dest
 
     mov rdi, [rsp]              ; Ast
     call parse_expr
@@ -820,7 +863,7 @@ parse_assignment_expr:
 .done:
     mov rax, [rsp + 16]         ; dest
     movzx rdx, byte [rsp + 8]   ; placeness
-    add rsp, 32
+    add rsp, 40
     pop rbp
     ret
 
@@ -843,12 +886,16 @@ ast_parse_let:
     ; }
     ; end-structs
 
-    ; AstNode [8..32]
+    ; span: u64 [40..48]
+    ; AstNode [8..40]
     ; AstVarDecl [8..40]
     ; Ast [0..8]
     sub rsp, 48
     mov [rsp], rdi              ; Ast
 
+    call tokeniser_get_cursor
+    mov [rsp + 40], rax         ; span
+
     ; skipped in parse_statement 
     ; mov dil, TOKEN_LET
     ; call unwrap_token
@@ -875,11 +922,13 @@ ast_parse_let:
     call memcpy
 
     mov qword [rsp + 8], AST_VAR_DECL ; AstNode.kind
-    mov [rsp + 16], rdi                ; AstNode.data
-    mov qword [rsp + 24], 0            ; AstNode.extra
+    mov [rsp + 16], rdi               ; AstNode.data
+    mov qword [rsp + 24], 0           ; AstNode.extra
+    mov rdi, [rsp + 40]               ; span
+    mov [rsp + 32], rdi               ; AstNode.span
 
     mov rdi, [rsp]              ; Ast
-    lea rsi, [rsp + 8]         ; &AstNode
+    lea rsi, [rsp + 8]          ; &AstNode
     call vec_push
     ; variable is already a place
 
@@ -924,17 +973,26 @@ ast_value_to_place:
     mov rax, rsi
     je .done
     ; create new AST node
-    sub rsp, 32
-    mov [rsp], rdi
-    mov byte [rsp + 8], AST_VALUE_TO_PLACE ; kind
-    mov [rsp + 16], rsi                    ; data
-    mov qword [rsp + 24], 0                ; extra
+    sub rsp, 40
+    mov [rsp], rdi              ; Ast
+    mov [rsp + 8], rsi          ; node_index
+
+    ; load original node's span
+    call vec_get
+    mov rdi, [rax + 24]         ; AstNode.span
+    mov [rsp + 32], rdi         ; AstNode.span
+
+    mov rsi, [rsp + 8]                     ; node_index
+    mov byte [rsp + 8], AST_VALUE_TO_PLACE ; AstNode.kind
+    mov [rsp + 16], rsi                    ; AstNode.data
+    mov qword [rsp + 24], 0                ; AstNode.extra
     lea rsi, [rsp + 8]                     ; &AstNode
+    mov rdi, [rsp]                         ; Ast
     call vec_push
-    mov rdi, [rsp]                 ; Ast
-    mov rax, [rdi + 8]            ; Ast.nodes.len()
+    mov rdi, [rsp]              ; Ast
+    mov rax, [rdi + 8]          ; Ast.nodes.len()
     dec rax
-    add rsp, 32
+    add rsp, 40
 .done:
     pop rbp
     ret
@@ -951,17 +1009,26 @@ ast_place_to_value:
     mov rax, rsi
     je .done
     ; create new AST node
-    sub rsp, 32
-    mov [rsp], rdi
-    mov byte [rsp + 8], AST_PLACE_TO_VALUE ; kind
-    mov [rsp + 16], rsi                    ; data
-    mov qword [rsp + 24], 0                ; extra
+    sub rsp, 40
+    mov [rsp], rdi              ; Ast
+    mov [rsp + 8], rsi          ; node_index
+
+    ; load original node's span
+    call vec_get
+    mov rdi, [rax + 24]         ; AstNode.span
+    mov [rsp + 32], rdi         ; AstNode.span
+
+    mov rsi, [rsp + 8]                     ; node_index
+    mov byte [rsp + 8], AST_PLACE_TO_VALUE ; AstNode.kind
+    mov [rsp + 16], rsi                    ; AstNode.data
+    mov qword [rsp + 24], 0                ; AstNode.extra
     lea rsi, [rsp + 8]                     ; &AstNode
+    mov rdi, [rsp]                         ; Ast
     call vec_push
-    mov rdi, [rsp]                 ; Ast
-    mov rax, [rdi + 8]            ; Ast.nodes.len()
+    mov rdi, [rsp]              ; Ast
+    mov rax, [rdi + 8]          ; Ast.nodes.len()
     dec rax
-    add rsp, 32
+    add rsp, 40
 .done:
     pop rbp
     ret
@@ -1164,19 +1231,17 @@ ast_build_symtable_for_each:
     mov byte [rsp + 32], SYM_KEY_SCOPE ; SymKey.kind
     mov rdx, [rsp + 16]            ; index
     mov qword [rsp + 40], rdx      ; SymKey.scope_index
-    mov qword [rsp + 48], 0        ; SymKey.span
+    mov rdx, [rax + 24]            ; AstNode.span
+    mov qword [rsp + 48], rdx      ; SymKey.span
     mov qword [rsp + 56], 1        ; SymKey.ident
     mov qword [rsp + 64], 0        ; SymKey.ident_len
 
-    ; mov rbx, [rax + 16]         ; AstNode.data
-    ; mov rdx, [rbx + 8]          ; Func.name
-    ; mov rcx, [rbx + 16]         ; Func.name_len
     mov rbx, [rax + 8]          ; AstNode.data
     mov rdx, [rbx + 0]          ; Func.name
     mov rcx, [rbx + 8]          ; Func.name_len
 
-    mov qword [rsp + 72], rdx   ; SymEntry.index
-    mov qword [rsp + 80], rcx   ; SymEntry.extra
+    mov [rsp + 72], rdx   ; SymEntry.index
+    mov [rsp + 80], rcx   ; SymEntry.extra
 
     mov rdi, [rsp + 8]          ; *Ctx
     lea rdi, [rdi + 40]         ; Ctx.symtable
@@ -1196,8 +1261,8 @@ ast_build_symtable_for_each:
     ; insert variable entry
     mov byte [rsp + 32], SYM_KEY_VAR ; SymKey.kind
 
-    ; TODO: set span correctly
-    mov qword [rsp + 48], 0     ; SymKey.span
+    mov rdx, [rax + 24]         ; AstNode.span
+    mov qword [rsp + 48], rdx   ; SymKey.span
 
     mov rbx, [rsp + 24]         ; AstNode.data
     mov rbx, [rbx + 8]          ; AstNode.data
@@ -1232,8 +1297,8 @@ ast_build_symtable_for_each:
     ; insert variable entry
     mov byte [rsp + 32], SYM_KEY_ARG ; SymKey.kind
 
-    ; TODO: set span correctly
-    mov qword [rsp + 48], 0     ; SymKey.span
+    mov rdx, [rax + 24]         ; AstNode.span
+    mov qword [rsp + 48], rdx   ; SymKey.span
 
     mov rbx, [rsp + 24]         ; *AstNode
     mov rbx, [rbx + 8]          ; AstNode.data
diff --git a/lang/tests/ast.rs b/lang/tests/ast.rs
index deaded3..0b42a40 100644
--- a/lang/tests/ast.rs
+++ b/lang/tests/ast.rs
@@ -48,7 +48,7 @@ fn main() {
         };
     }
 
-    // print_ast(b"3 + 4", |ast| unsafe { parse_expr(ast) });
+    print_ast(b"3 + 4", |ast| unsafe { parse_expr(ast) });
     // print_ast(b"fn main() -> void { return 1 + 2; }", |ast| unsafe {
     //     parse_func(ast)
     // });
diff --git a/lang/tests/shared/defs.rs b/lang/tests/shared/defs.rs
index 8688eb5..fdc9b4e 100644
--- a/lang/tests/shared/defs.rs
+++ b/lang/tests/shared/defs.rs
@@ -106,6 +106,7 @@ pub struct AstNode {
     pub kind: u8,
     pub data: *const (),
     pub extra: usize,
+    pub span: u64,
 }
 
 #[repr(C)]