From ad7fb5d0fcbd620d67fceb0bdd0bd949e548cb9e Mon Sep 17 00:00:00 2001
From: Jakub Doka <jakub.doka2@gmail.com>
Date: Mon, 11 Nov 2024 22:34:42 +0100
Subject: [PATCH] adding errors for useless type hints

---
 lang/README.md  |  6 +++---
 lang/src/son.rs | 12 +++++++++---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/lang/README.md b/lang/README.md
index 50c0c55..2442126 100644
--- a/lang/README.md
+++ b/lang/README.md
@@ -646,7 +646,7 @@ main := fn(): int {
 				i -= 1
 			}
 			//   b g r
-			put_pixel(.(x, y), .(@as(u8, @intcast(i)), @as(u8, @intcast(i)), @as(u8, @intcast(i)), 255))
+			put_pixel(.(x, y), .(@intcast(i), @intcast(i), @intcast(i), 255))
 		}
 	}
 
@@ -1030,7 +1030,7 @@ main := fn(): uint {
 ```hb
 Color := struct {r: u8, g: u8, b: u8, a: u8}
 white := Color.(255, 255, 255, 255)
-u32_to_color := fn(v: u32): Color return @as(Color, @bitcast(u32_to_u32(@bitcast(v))))
+u32_to_color := fn(v: u32): Color return @bitcast(u32_to_u32(@bitcast(v)))
 u32_to_u32 := fn(v: u32): u32 return v
 main := fn(): uint {
 	return u32_to_color(@bitcast(white)).r
@@ -1399,7 +1399,7 @@ main := fn(): uint {
 	}
 	n = 1
 	loop if n >= 10 break else {
-		*(@as(^[u8; 1024], @bitcast(&back_buffer)) + n) = *@as(^[u8; 1024], @bitcast(&back_buffer))
+		*(@as(^[u8; 1024], @bitcast(&back_buffer)) + n) = *@bitcast(&back_buffer)
 		n += 1
 	}
 	return back_buffer[1024 * 2]
diff --git a/lang/src/son.rs b/lang/src/son.rs
index 52ba57a..1d1d7bc 100644
--- a/lang/src/son.rs
+++ b/lang/src/son.rs
@@ -3168,10 +3168,16 @@ impl<'a> Codegen<'a> {
                     self.tys,
                 ))
             }
-            Expr::Directive { name: "as", args: [ty, expr], .. } => {
+            Expr::Directive { name: "as", args: [ty, expr], pos } => {
                 let ty = self.ty(ty);
-                let ctx = Ctx::default().with_ty(ty);
-                let mut val = self.raw_expr_ctx(expr, ctx)?;
+                let mut val = self.raw_expr_ctx(expr, Ctx::default().with_ty(ty))?;
+
+                if let Some(ity) = ctx.ty
+                    && ity.try_upcast(ty) == Some(ty)
+                    && val.ty == ity
+                {
+                    self.report(pos, "the type is known at this point, remove the hint");
+                }
                 self.strip_var(&mut val);
                 self.assert_ty(expr.pos(), &mut val, ty, "hinted expr");
                 Some(val)