Introduce VarBindingIntroduction.

Author: cjgillot

compiler/rustc_middle/src/mir/mod.rs

@@ -884,8 +884,9 @@ pub struct VarBindingForm<'tcx> {
     pub opt_match_place: Option<(Option<Place<'tcx>>, Span)>,
     /// The span of the pattern in which this variable was bound.
     pub pat_span: Span,
-    /// For each introduction place, record here the span and whether this was a shorthand pattern.
-    pub introductions: Vec<(Span, /* is_shorthand */ bool)>,
+    /// A binding can be introduced multiple times, with or patterns:
+    /// `Foo::A { x } | Foo::B { z: x }`. This stores information for each of those introductions.
+    pub introductions: Vec<VarBindingIntroduction>,
 }
 
 #[derive(Clone, Debug, TyEncodable, TyDecodable)]
@@ -898,6 +899,14 @@ pub enum BindingForm<'tcx> {
     RefForGuard,
 }
 
+#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
+pub struct VarBindingIntroduction {
+    /// Where this additional introduction happened.
+    pub span: Span,
+    /// Is that introduction a shorthand struct pattern, i.e. `Foo { x }`.
+    pub is_shorthand: bool,
+}
+
 mod binding_form_impl {
     use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
     use rustc_query_system::ich::StableHashingContext;

compiler/rustc_middle/src/thir.rs

@@ -798,6 +798,7 @@ pub enum PatKind<'tcx> {
         /// (The same binding can occur multiple times in different branches of
         /// an or-pattern, but only one of them will be primary.)
         is_primary: bool,
+        /// Is this binding a shorthand struct pattern, i.e. `Foo { a }`?
         is_shorthand: bool,
     },
 

compiler/rustc_mir_build/src/builder/matches/mod.rs

@@ -817,7 +817,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
         let local_info = self.local_decls[local_id].local_info.as_mut().unwrap_crate_local();
         if let LocalInfo::User(BindingForm::Var(var_info)) = &mut **local_info {
-            var_info.introductions.push((span, is_shorthand));
+            var_info.introductions.push(VarBindingIntroduction { span, is_shorthand });
         }
         Place::from(local_id)
     }

compiler/rustc_mir_build/src/builder/mod.rs

@@ -1068,7 +1068,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                                 opt_ty_info: param.ty_span,
                                 opt_match_place: Some((None, span)),
                                 pat_span: span,
-                                introductions: vec![(span, false)],
+                                introductions: vec![VarBindingIntroduction {
+                                    span,
+                                    is_shorthand: false,
+                                }],
                             }))
                         };
                     self.var_indices.insert(var, LocalsForNode::One(local));