Simplify RvalueCandidateType.

There is no difference between the Patternand Borrow cases. Reduce it to
a simple struct.

Author: m-ou-se

compiler/rustc_hir_analysis/src/check/region.rs

@@ -623,10 +623,7 @@ fn resolve_local<'tcx>(
             if is_binding_pat(pat) {
                 visitor.scope_tree.record_rvalue_candidate(
                     expr.hir_id,
-                    RvalueCandidateType::Pattern {
-                        target: expr.hir_id.local_id,
-                        lifetime: blk_scope,
-                    },
+                    RvalueCandidate { target: expr.hir_id.local_id, lifetime: blk_scope },
                 );
             }
         }
@@ -731,10 +728,7 @@ fn resolve_local<'tcx>(
                 record_rvalue_scope_if_borrow_expr(visitor, subexpr, blk_id);
                 visitor.scope_tree.record_rvalue_candidate(
                     subexpr.hir_id,
-                    RvalueCandidateType::Borrow {
-                        target: subexpr.hir_id.local_id,
-                        lifetime: blk_id,
-                    },
+                    RvalueCandidate { target: subexpr.hir_id.local_id, lifetime: blk_id },
                 );
             }
             hir::ExprKind::Struct(_, fields, _) => {

compiler/rustc_hir_typeck/src/rvalue_scopes.rs

@@ -2,7 +2,7 @@ use hir::Node;
 use hir::def_id::DefId;
 use rustc_hir as hir;
 use rustc_middle::bug;
-use rustc_middle::middle::region::{RvalueCandidateType, Scope, ScopeTree};
+use rustc_middle::middle::region::{RvalueCandidate, Scope, ScopeTree};
 use rustc_middle::ty::RvalueScopes;
 use tracing::debug;
 
@@ -55,15 +55,11 @@ fn record_rvalue_scope_rec(
 fn record_rvalue_scope(
     rvalue_scopes: &mut RvalueScopes,
     expr: &hir::Expr<'_>,
-    candidate: &RvalueCandidateType,
+    candidate: &RvalueCandidate,
 ) {
     debug!("resolve_rvalue_scope(expr={expr:?}, candidate={candidate:?})");
-    match candidate {
-        RvalueCandidateType::Borrow { lifetime, .. }
-        | RvalueCandidateType::Pattern { lifetime, .. } => {
-            record_rvalue_scope_rec(rvalue_scopes, expr, *lifetime)
-        } // FIXME(@dingxiangfei2009): handle the candidates in the function call arguments
-    }
+    record_rvalue_scope_rec(rvalue_scopes, expr, candidate.lifetime)
+    // FIXME(@dingxiangfei2009): handle the candidates in the function call arguments
 }
 
 pub(crate) fn resolve_rvalue_scopes<'a, 'tcx>(

compiler/rustc_middle/src/middle/region.rs

@@ -224,7 +224,7 @@ pub struct ScopeTree {
     /// and not the enclosing *statement*. Expressions that are not present in this
     /// table are not rvalue candidates. The set of rvalue candidates is computed
     /// during type check based on a traversal of the AST.
-    pub rvalue_candidates: HirIdMap<RvalueCandidateType>,
+    pub rvalue_candidates: HirIdMap<RvalueCandidate>,
 
     /// Backwards incompatible scoping that will be introduced in future editions.
     /// This information is used later for linting to identify locals and
@@ -308,15 +308,14 @@ pub struct ScopeTree {
     pub yield_in_scope: UnordMap<Scope, Vec<YieldData>>,
 }
 
-/// Identifies the reason that a given expression is an rvalue candidate
-/// (see the `rvalue_candidates` field for more information what rvalue
-/// candidates in general). In constants, the `lifetime` field is None
-/// to indicate that certain expressions escape into 'static and
-/// should have no local cleanup scope.
+/// See the `rvalue_candidates` field for more information on rvalue
+/// candidates in general.
+/// The `lifetime` field is None to indicate that certain expressions escape
+/// into 'static and should have no local cleanup scope.
 #[derive(Debug, Copy, Clone, HashStable)]
-pub enum RvalueCandidateType {
-    Borrow { target: hir::ItemLocalId, lifetime: Option<Scope> },
-    Pattern { target: hir::ItemLocalId, lifetime: Option<Scope> },
+pub struct RvalueCandidate {
+    pub target: hir::ItemLocalId,
+    pub lifetime: Option<Scope>,
 }
 
 #[derive(Debug, Copy, Clone, HashStable)]
@@ -344,16 +343,12 @@ impl ScopeTree {
         self.var_map.insert(var, lifetime);
     }
 
-    pub fn record_rvalue_candidate(&mut self, var: HirId, candidate_type: RvalueCandidateType) {
-        debug!("record_rvalue_candidate(var={var:?}, type={candidate_type:?})");
-        match &candidate_type {
-            RvalueCandidateType::Borrow { lifetime: Some(lifetime), .. }
-            | RvalueCandidateType::Pattern { lifetime: Some(lifetime), .. } => {
-                assert!(var.local_id != lifetime.local_id)
-            }
-            _ => {}
+    pub fn record_rvalue_candidate(&mut self, var: HirId, candidate: RvalueCandidate) {
+        debug!("record_rvalue_candidate(var={var:?}, candidate={candidate:?})");
+        if let Some(lifetime) = &candidate.lifetime {
+            assert!(var.local_id != lifetime.local_id)
         }
-        self.rvalue_candidates.insert(var, candidate_type);
+        self.rvalue_candidates.insert(var, candidate);
     }
 
     /// Returns the narrowest scope that encloses `id`, if any.