From e4c71f1fd8caf703dde7edb75b3cd33585aadddc Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sun, 14 Apr 2024 09:21:38 -0400
Subject: [PATCH] Fix value suggestion for array in generic context

---
 compiler/rustc_trait_selection/src/lib.rs      |  1 +
 .../src/traits/error_reporting/suggestions.rs  |  8 +++-----
 tests/ui/consts/value-suggestion-ice-123906.rs |  8 ++++++++
 .../consts/value-suggestion-ice-123906.stderr  | 18 ++++++++++++++++++
 4 files changed, 30 insertions(+), 5 deletions(-)
 create mode 100644 tests/ui/consts/value-suggestion-ice-123906.rs
 create mode 100644 tests/ui/consts/value-suggestion-ice-123906.stderr

diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index b5fb710e4cc..057d00aeae8 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -22,6 +22,7 @@
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
 #![feature(extract_if)]
+#![feature(if_let_guard)]
 #![feature(let_chains)]
 #![feature(option_take_if)]
 #![feature(never_type)]
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 6ae7cbf717b..36fb5c8a6f7 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -4583,11 +4583,9 @@ fn ty_kind_suggestion(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> Opt
                     format!("&{}{ty}", mutability.prefix_str())
                 }
             }
-            ty::Array(ty, len) => format!(
-                "[{}; {}]",
-                self.ty_kind_suggestion(param_env, *ty)?,
-                len.eval_target_usize(tcx, ty::ParamEnv::reveal_all()),
-            ),
+            ty::Array(ty, len) if let Some(len) = len.try_eval_target_usize(tcx, param_env) => {
+                format!("[{}; {}]", self.ty_kind_suggestion(param_env, *ty)?, len)
+            }
             ty::Tuple(tys) => format!(
                 "({})",
                 tys.iter()
diff --git a/tests/ui/consts/value-suggestion-ice-123906.rs b/tests/ui/consts/value-suggestion-ice-123906.rs
new file mode 100644
index 00000000000..531bbc15852
--- /dev/null
+++ b/tests/ui/consts/value-suggestion-ice-123906.rs
@@ -0,0 +1,8 @@
+fn as_chunks<const N: usize>() -> [u8; N] {
+    loop {
+        break;
+        //~^ ERROR mismatched types
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/consts/value-suggestion-ice-123906.stderr b/tests/ui/consts/value-suggestion-ice-123906.stderr
new file mode 100644
index 00000000000..8e2c316400d
--- /dev/null
+++ b/tests/ui/consts/value-suggestion-ice-123906.stderr
@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+  --> $DIR/value-suggestion-ice-123906.rs:3:9
+   |
+LL | fn as_chunks<const N: usize>() -> [u8; N] {
+   |                                   ------- expected `[u8; ]` because of this return type
+LL |     loop {
+   |     ---- this loop is expected to be of type `[u8; N]`
+LL |         break;
+   |         ^^^^^ expected `[u8; N]`, found `()`
+   |
+help: give the `break` a value of the expected type
+   |
+LL |         break value;
+   |               +++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.