From 1e578b11445c390eb36d1f3e97f3a27ab3667d0a Mon Sep 17 00:00:00 2001
From: Turiiya <34311583+ttytm@users.noreply.github.com>
Date: Sun, 29 Oct 2023 13:25:15 +0100
Subject: [PATCH] checker: extend byte deprecation warnings to return types
 (#19668)

---
 vlib/builtin/string.v       | 6 ++----
 vlib/json/json_primitives.v | 4 ++--
 vlib/v/checker/fn.v         | 3 +++
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 59298546fd28f8..71f2d4622fd372 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -1735,15 +1735,13 @@ pub fn (s string) str() string {
 
 // at returns the byte at index `idx`.
 // Example: assert 'ABC'.at(1) == u8(`B`)
-fn (s string) at(idx int) byte {
+fn (s string) at(idx int) u8 {
 	$if !no_bounds_checking {
 		if idx < 0 || idx >= s.len {
 			panic('string index out of range: ${idx} / ${s.len}')
 		}
 	}
-	unsafe {
-		return s.str[idx]
-	}
+	return unsafe { s.str[idx] }
 }
 
 // version of `at()` that is used in `a[i] or {`
diff --git a/vlib/json/json_primitives.v b/vlib/json/json_primitives.v
index a2b18af4a940c7..64b5e877888a0e 100644
--- a/vlib/json/json_primitives.v
+++ b/vlib/json/json_primitives.v
@@ -86,8 +86,8 @@ fn decode_i64(root &C.cJSON) i64 {
 
 // TODO: remove when `byte` is removed
 [markused]
-fn decode_byte(root &C.cJSON) byte {
-	return byte(decode_u8(root))
+fn decode_byte(root &C.cJSON) u8 {
+	return decode_u8(root)
 }
 
 [markused]
diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index c6ca201bdbcdbf..43382eb949dc6a 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -126,6 +126,9 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 				c.table.find_or_register_array_fixed(parent_sym.info.elem_type, parent_sym.info.size,
 					parent_sym.info.size_expr, true)
 			}
+			if return_sym.name == 'byte' {
+				c.warn('byte is deprecated, use u8 instead', node.return_type_pos)
+			}
 		}
 		final_return_sym := c.table.final_sym(node.return_type)
 		if final_return_sym.info is ast.MultiReturn {