diff --git a/gcc/rust/typecheck/rust-casts.cc b/gcc/rust/typecheck/rust-casts.cc
index 75b2872104fd..7439debb916c 100644
--- a/gcc/rust/typecheck/rust-casts.cc
+++ b/gcc/rust/typecheck/rust-casts.cc
@@ -300,11 +300,33 @@ TypeCastRules::check_ptr_ptr_cast ()
 void
 TypeCastRules::emit_cast_error () const
 {
-  // error[E0604]
   rich_location r (line_table, locus);
   r.add_range (from.get_locus ());
   r.add_range (to.get_locus ());
-  rust_error_at (r, ErrorCode::E0054, "invalid cast %<%s%> to %<%s%>",
+  ErrorCode error_code;
+  std::string error_msg;
+  switch (to.get_ty ()->get_kind ())
+    {
+    case TyTy::TypeKind::BOOL:
+      error_msg = "cannot cast %qs as %qs";
+      error_code = ErrorCode::E0054;
+      break;
+    case TyTy::TypeKind::CHAR:
+      error_msg
+	+= "cannot cast %qs as %qs, only %<u8%> can be cast as %<char%>";
+      error_code = ErrorCode::E0604;
+      break;
+    case TyTy::TypeKind::SLICE:
+      error_msg = "cast to unsized type: %qs as %qs";
+      error_code = ErrorCode::E0620;
+      break;
+
+    default:
+      error_msg = "casting %qs as %qs is invalid";
+      error_code = ErrorCode::E0606;
+      break;
+    }
+  rust_error_at (r, error_code, error_msg.c_str (),
 		 from.get_ty ()->get_name ().c_str (),
 		 to.get_ty ()->get_name ().c_str ());
 }
diff --git a/gcc/testsuite/rust/compile/all-cast.rs b/gcc/testsuite/rust/compile/all-cast.rs
new file mode 100644
index 000000000000..fa24373a6779
--- /dev/null
+++ b/gcc/testsuite/rust/compile/all-cast.rs
@@ -0,0 +1,11 @@
+fn main() {
+    let x = 5;
+    let x_is_nonzero = x as bool; // { dg-error "cannot cast .<integer>. as .bool." }
+
+    0u32 as char; // { dg-error "cannot cast .u32. as .char., only .u8. can be cast as .char." }
+
+    let x = &[1_usize, 2] as [usize]; // { dg-error "cast to unsized type: .& .usize:CAPACITY.. as ..usize.." }
+
+    let a = &0u8; // Here, `x` is a `&u8`.
+    let y: u32 = a as u32; // { dg-error "casting .& u8. as .u32. is invalid" }
+}
diff --git a/gcc/testsuite/rust/compile/bad_as_bool_char.rs b/gcc/testsuite/rust/compile/bad_as_bool_char.rs
index 9652915fe117..1828d2256f29 100644
--- a/gcc/testsuite/rust/compile/bad_as_bool_char.rs
+++ b/gcc/testsuite/rust/compile/bad_as_bool_char.rs
@@ -2,17 +2,17 @@ pub fn main ()
 {
   let t = true;
   let f = false;
-  let fone = t as f32;   // { dg-error "invalid cast" }
-  let fzero = f as f64;  // { dg-error "invalid cast" }
+  let fone = t as f32;   // { dg-error "casting .bool. as .f32. is invalid" }
+  let fzero = f as f64;  // { dg-error "casting .bool. as .f64. is invalid" }
 
-  let nb = 0u8 as bool;  // { dg-error "invalid cast .u8. to .bool. \\\[E0054\\\]" }
-  let nc = true as char; // { dg-error "invalid cast" }
+  let nb = 0u8 as bool;  // { dg-error "cannot cast .u8. as .bool." }
+  let nc = true as char; // { dg-error "cannot cast .bool. as .char., only .u8. can be cast as .char." }
 
   let a = 'a';
   let b = 'b';
-  let fa = a as f32;     // { dg-error "invalid cast" }
-  let bb = b as bool;    // { dg-error "invalid cast .char. to .bool. \\\[E0054\\\]" }
+  let fa = a as f32;     // { dg-error "casting .char. as .f32. is invalid" }
+  let bb = b as bool;    // { dg-error "cannot cast .char. as .bool." }
 
   let t32: u32 = 33;
-  let ab = t32 as char;  // { dg-error "invalid cast" }
+  let ab = t32 as char;  // { dg-error "cannot cast .u32. as .char., only .u8. can be cast as .char." }
 }
diff --git a/gcc/testsuite/rust/compile/cast1.rs b/gcc/testsuite/rust/compile/cast1.rs
index 74c4b1eaac4c..0472d582db84 100644
--- a/gcc/testsuite/rust/compile/cast1.rs
+++ b/gcc/testsuite/rust/compile/cast1.rs
@@ -1,5 +1,5 @@
 fn main() {
     let a: i32 = 123;
     let b = a as char;
-    // { dg-error "invalid cast .i32. to .char." "" { target *-*-* } .-1 }
+    // { dg-error "cannot cast .i32. as .char., only .u8. can be cast as .char." "" { target *-*-* } .-1 }
 }
diff --git a/gcc/testsuite/rust/compile/cast4.rs b/gcc/testsuite/rust/compile/cast4.rs
index ab00010e35b1..22ac0c5acf7e 100644
--- a/gcc/testsuite/rust/compile/cast4.rs
+++ b/gcc/testsuite/rust/compile/cast4.rs
@@ -1,5 +1,5 @@
 fn main() {
     let a: i32 = 123;
     let u = a as bool;
-    // { dg-error "invalid cast .i32. to .bool." "" { target *-*-* } .-1 }
+    // { dg-error "cannot cast .i32. as .bool." "" { target *-*-* } .-1 }
 }
diff --git a/gcc/testsuite/rust/compile/cast5.rs b/gcc/testsuite/rust/compile/cast5.rs
index ecc10c1490a6..2e340dd4fe4b 100644
--- a/gcc/testsuite/rust/compile/cast5.rs
+++ b/gcc/testsuite/rust/compile/cast5.rs
@@ -1,11 +1,11 @@
 fn main() {
     const A: char = 0x1F888 as char;
-    // { dg-error "invalid cast .<integer>. to .char." "" { target *-*-* } .-1 }
+    // { dg-error "cannot cast .<integer>. as .char., only .u8. can be cast as .char." "" { target *-*-* } .-1 }
     const B: char = 129160 as char;
-    // { dg-error "invalid cast .<integer>. to .char." "" { target *-*-* } .-1 }
+    // { dg-error "cannot cast .<integer>. as .char., only .u8. can be cast as .char." "" { target *-*-* } .-1 }
     const C: i32 = 42;
     const D: char = C as char;
-    // { dg-error "invalid cast .i32. to .char." "" { target *-*-* } .-1 }
+    // { dg-error "cannot cast .i32. as .char., only .u8. can be cast as .char." "" { target *-*-* } .-1 }
     const E: char = '\u{01F888}';
     const F: u8 = 42; 
     const G: char= F as char;