From ca56739366e5183d68eaec1a2a9ee6429fd4002f Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 23 Nov 2023 06:47:02 +0000
Subject: [PATCH] Remove 3 more unused ObligationCauseCodes

---
 compiler/rustc_middle/src/traits/mod.rs                  | 9 ---------
 .../src/traits/error_reporting/suggestions.rs            | 5 -----
 .../src/traits/error_reporting/type_err_ctxt_ext.rs      | 1 -
 3 files changed, 15 deletions(-)

diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 6cc4803c910..853eea1a609 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -370,9 +370,6 @@ pub enum ObligationCauseCode<'tcx> {
         origin_expr: bool,
     },
 
-    /// Constants in patterns must have `Structural` type.
-    ConstPatternStructural,
-
     /// Computing common supertype in an if expression
     IfExpression(Box<IfExpressionCause<'tcx>>),
 
@@ -405,9 +402,6 @@ pub enum ObligationCauseCode<'tcx> {
     /// `return` with an expression
     ReturnValue(hir::HirId),
 
-    /// Return type of this function
-    ReturnType,
-
     /// Opaque return type of this function
     OpaqueReturnType(Option<(Ty<'tcx>, Span)>),
 
@@ -417,9 +411,6 @@ pub enum ObligationCauseCode<'tcx> {
     /// #[feature(trivial_bounds)] is not enabled
     TrivialBound,
 
-    /// If `X` is the concrete type of an opaque type `impl Y`, then `X` must implement `Y`
-    OpaqueType,
-
     AwaitableExpr(hir::HirId),
 
     ForLoopIterator,
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 47eaca90d1b..f73e6f144df 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -2592,11 +2592,9 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             | ObligationCauseCode::MethodReceiver
             | ObligationCauseCode::ReturnNoExpression
             | ObligationCauseCode::UnifyReceiver(..)
-            | ObligationCauseCode::OpaqueType
             | ObligationCauseCode::MiscObligation
             | ObligationCauseCode::WellFormed(..)
             | ObligationCauseCode::MatchImpl(..)
-            | ObligationCauseCode::ReturnType
             | ObligationCauseCode::ReturnValue(_)
             | ObligationCauseCode::BlockTailExpression(..)
             | ObligationCauseCode::AwaitableExpr(_)
@@ -2974,9 +2972,6 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     "all values live across `{what}` must have a statically known size"
                 ));
             }
-            ObligationCauseCode::ConstPatternStructural => {
-                err.note("constants used for pattern-matching must derive `PartialEq` and `Eq`");
-            }
             ObligationCauseCode::SharedStatic => {
                 err.note("shared static variables must have a type that implements `Sync`");
             }
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 5c28fec3960..5718ab3b966 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -1448,7 +1448,6 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         | ObligationCauseCode::ExprItemObligation(..)
                         | ObligationCauseCode::ExprBindingObligation(..)
                         | ObligationCauseCode::Coercion { .. }
-                        | ObligationCauseCode::OpaqueType
                 );
 
                 // constrain inference variables a bit more to nested obligations from normalize so