Auto merge of #47837 - eddyb:going-places, r=nikomatsakis

Replace "lvalue" terminology with "place".

See #46425 for the previous PR (which only changed MIR-related code).

r? @nikomatsakis

src/librustc/middle/liveness.rs

@@ -1034,10 +1034,10 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
           }
 
           hir::ExprAssign(ref l, ref r) => {
-            // see comment on lvalues in
-            // propagate_through_lvalue_components()
-            let succ = self.write_lvalue(&l, succ, ACC_WRITE);
-            let succ = self.propagate_through_lvalue_components(&l, succ);
+            // see comment on places in
+            // propagate_through_place_components()
+            let succ = self.write_place(&l, succ, ACC_WRITE);
+            let succ = self.propagate_through_place_components(&l, succ);
             self.propagate_through_expr(&r, succ)
           }
 
@@ -1047,11 +1047,11 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                 let succ = self.propagate_through_expr(&l, succ);
                 self.propagate_through_expr(&r, succ)
             } else {
-                // see comment on lvalues in
-                // propagate_through_lvalue_components()
-                let succ = self.write_lvalue(&l, succ, ACC_WRITE|ACC_READ);
+                // see comment on places in
+                // propagate_through_place_components()
+                let succ = self.write_place(&l, succ, ACC_WRITE|ACC_READ);
                 let succ = self.propagate_through_expr(&r, succ);
-                self.propagate_through_lvalue_components(&l, succ)
+                self.propagate_through_place_components(&l, succ)
             }
           }
 
@@ -1121,14 +1121,14 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
           hir::ExprInlineAsm(ref ia, ref outputs, ref inputs) => {
             let succ = ia.outputs.iter().zip(outputs).rev().fold(succ, |succ, (o, output)| {
-                // see comment on lvalues
-                // in propagate_through_lvalue_components()
+                // see comment on places
+                // in propagate_through_place_components()
                 if o.is_indirect {
                     self.propagate_through_expr(output, succ)
                 } else {
                     let acc = if o.is_rw { ACC_WRITE|ACC_READ } else { ACC_WRITE };
-                    let succ = self.write_lvalue(output, succ, acc);
-                    self.propagate_through_lvalue_components(output, succ)
+                    let succ = self.write_place(output, succ, acc);
+                    self.propagate_through_place_components(output, succ)
                 }
             });
 
@@ -1146,11 +1146,11 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         }
     }
 
-    fn propagate_through_lvalue_components(&mut self,
+    fn propagate_through_place_components(&mut self,
                                            expr: &Expr,
                                            succ: LiveNode)
                                            -> LiveNode {
-        // # Lvalues
+        // # Places
         //
         // In general, the full flow graph structure for an
         // assignment/move/etc can be handled in one of two ways,
@@ -1160,15 +1160,15 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         //
         // The two kinds of graphs are:
         //
-        //    Tracked lvalue          Untracked lvalue
+        //    Tracked place          Untracked place
         // ----------------------++-----------------------
         //                       ||
         //         |             ||           |
         //         v             ||           v
         //     (rvalue)          ||       (rvalue)
         //         |             ||           |
         //         v             ||           v
-        // (write of lvalue)     ||   (lvalue components)
+        // (write of place)     ||   (place components)
         //         |             ||           |
         //         v             ||           v
         //      (succ)           ||        (succ)
@@ -1177,25 +1177,25 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         //
         // I will cover the two cases in turn:
         //
-        // # Tracked lvalues
+        // # Tracked places
         //
-        // A tracked lvalue is a local variable/argument `x`.  In
+        // A tracked place is a local variable/argument `x`.  In
         // these cases, the link_node where the write occurs is linked
-        // to node id of `x`.  The `write_lvalue()` routine generates
+        // to node id of `x`.  The `write_place()` routine generates
         // the contents of this node.  There are no subcomponents to
         // consider.
         //
-        // # Non-tracked lvalues
+        // # Non-tracked places
         //
-        // These are lvalues like `x[5]` or `x.f`.  In that case, we
+        // These are places like `x[5]` or `x.f`.  In that case, we
         // basically ignore the value which is written to but generate
         // reads for the components---`x` in these two examples.  The
         // components reads are generated by
-        // `propagate_through_lvalue_components()` (this fn).
+        // `propagate_through_place_components()` (this fn).
         //
-        // # Illegal lvalues
+        // # Illegal places
         //
-        // It is still possible to observe assignments to non-lvalues;
+        // It is still possible to observe assignments to non-places;
         // these errors are detected in the later pass borrowck.  We
         // just ignore such cases and treat them as reads.
 
@@ -1207,17 +1207,17 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
         }
     }
 
-    // see comment on propagate_through_lvalue()
-    fn write_lvalue(&mut self, expr: &Expr, succ: LiveNode, acc: u32)
+    // see comment on propagate_through_place()
+    fn write_place(&mut self, expr: &Expr, succ: LiveNode, acc: u32)
                     -> LiveNode {
         match expr.node {
           hir::ExprPath(hir::QPath::Resolved(_, ref path)) => {
               self.access_path(expr.id, path, succ, acc)
           }
 
-          // We do not track other lvalues, so just propagate through
+          // We do not track other places, so just propagate through
           // to their subcomponents.  Also, it may happen that
-          // non-lvalues occur here, because those are detected in the
+          // non-places occur here, because those are detected in the
           // later pass borrowck.
           _ => succ
         }
@@ -1363,14 +1363,14 @@ fn check_arm<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, arm: &'tcx hir::Arm) {
 fn check_expr<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, expr: &'tcx Expr) {
     match expr.node {
       hir::ExprAssign(ref l, _) => {
-        this.check_lvalue(&l);
+        this.check_place(&l);
 
         intravisit::walk_expr(this, expr);
       }
 
       hir::ExprAssignOp(_, ref l, _) => {
         if !this.tables.is_method_call(expr) {
-            this.check_lvalue(&l);
+            this.check_place(&l);
         }
 
         intravisit::walk_expr(this, expr);
@@ -1381,10 +1381,10 @@ fn check_expr<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, expr: &'tcx Expr) {
           this.visit_expr(input);
         }
 
-        // Output operands must be lvalues
+        // Output operands must be places
         for (o, output) in ia.outputs.iter().zip(outputs) {
           if !o.is_indirect {
-            this.check_lvalue(output);
+            this.check_place(output);
           }
           this.visit_expr(output);
         }
@@ -1409,7 +1409,7 @@ fn check_expr<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, expr: &'tcx Expr) {
 }
 
 impl<'a, 'tcx> Liveness<'a, 'tcx> {
-    fn check_lvalue(&mut self, expr: &'tcx Expr) {
+    fn check_place(&mut self, expr: &'tcx Expr) {
         match expr.node {
             hir::ExprPath(hir::QPath::Resolved(_, ref path)) => {
                 if let Def::Local(nid) = path.def {
@@ -1423,7 +1423,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                 }
             }
             _ => {
-                // For other kinds of lvalues, no checks are required,
+                // For other kinds of places, no checks are required,
                 // and any embedded expressions are actually rvalues
                 intravisit::walk_expr(self, expr);
             }

src/librustc/middle/mem_categorization.rs

@@ -26,8 +26,8 @@
 //!       | E.comp    // access to an interior component
 //!
 //! Imagine a routine ToAddr(Expr) that evaluates an expression and returns an
-//! address where the result is to be found.  If Expr is an lvalue, then this
-//! is the address of the lvalue.  If Expr is an rvalue, this is the address of
+//! address where the result is to be found.  If Expr is a place, then this
+//! is the address of the place.  If Expr is an rvalue, this is the address of
 //! some temporary spot in memory where the result is stored.
 //!
 //! Now, cat_expr() classifies the expression Expr and the address A=ToAddr(Expr)
@@ -182,7 +182,7 @@ pub struct cmt_<'tcx> {
     pub id: ast::NodeId,           // id of expr/pat producing this value
     pub span: Span,                // span of same expr/pat
     pub cat: Categorization<'tcx>, // categorization of expr
-    pub mutbl: MutabilityCategory, // mutability of expr as lvalue
+    pub mutbl: MutabilityCategory, // mutability of expr as place
     pub ty: Ty<'tcx>,              // type of the expr (*see WARNING above*)
     pub note: Note,                // Note about the provenance of this cmt
 }
@@ -517,7 +517,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                     // a bind-by-ref means that the base_ty will be the type of the ident itself,
                     // but what we want here is the type of the underlying value being borrowed.
                     // So peel off one-level, turning the &T into T.
-                    match base_ty.builtin_deref(false, ty::NoPreference) {
+                    match base_ty.builtin_deref(false) {
                         Some(t) => t.ty,
                         None => {
                             debug!("By-ref binding of non-derefable type {:?}", base_ty);
@@ -603,7 +603,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         match expr.node {
           hir::ExprUnary(hir::UnDeref, ref e_base) => {
             if self.tables.is_method_call(expr) {
-                self.cat_overloaded_lvalue(expr, e_base, false)
+                self.cat_overloaded_place(expr, e_base, false)
             } else {
                 let base_cmt = self.cat_expr(&e_base)?;
                 self.cat_deref(expr, base_cmt, false)
@@ -631,7 +631,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                 // The call to index() returns a `&T` value, which
                 // is an rvalue. That is what we will be
                 // dereferencing.
-                self.cat_overloaded_lvalue(expr, base, true)
+                self.cat_overloaded_place(expr, base, true)
             } else {
                 let base_cmt = self.cat_expr(&base)?;
                 self.cat_index(expr, base_cmt, expr_ty, InteriorOffsetKind::Index)
@@ -983,27 +983,27 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         ret
     }
 
-    fn cat_overloaded_lvalue(&self,
+    fn cat_overloaded_place(&self,
                              expr: &hir::Expr,
                              base: &hir::Expr,
                              implicit: bool)
                              -> McResult<cmt<'tcx>> {
-        debug!("cat_overloaded_lvalue: implicit={}", implicit);
+        debug!("cat_overloaded_place: implicit={}", implicit);
 
         // Reconstruct the output assuming it's a reference with the
         // same region and mutability as the receiver. This holds for
         // `Deref(Mut)::Deref(_mut)` and `Index(Mut)::index(_mut)`.
-        let lvalue_ty = self.expr_ty(expr)?;
+        let place_ty = self.expr_ty(expr)?;
         let base_ty = self.expr_ty_adjusted(base)?;
 
         let (region, mutbl) = match base_ty.sty {
             ty::TyRef(region, mt) => (region, mt.mutbl),
             _ => {
-                span_bug!(expr.span, "cat_overloaded_lvalue: base is not a reference")
+                span_bug!(expr.span, "cat_overloaded_place: base is not a reference")
             }
         };
         let ref_ty = self.tcx.mk_ref(region, ty::TypeAndMut {
-            ty: lvalue_ty,
+            ty: place_ty,
             mutbl,
         });
 
@@ -1019,7 +1019,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         debug!("cat_deref: base_cmt={:?}", base_cmt);
 
         let base_cmt_ty = base_cmt.ty;
-        let deref_ty = match base_cmt_ty.builtin_deref(true, ty::NoPreference) {
+        let deref_ty = match base_cmt_ty.builtin_deref(true) {
             Some(mt) => mt.ty,
             None => {
                 debug!("Explicit deref of non-derefable type: {:?}",
@@ -1386,7 +1386,7 @@ impl<'tcx> cmt_<'tcx> {
         }
     }
 
-    /// Returns `FreelyAliasable(_)` if this lvalue represents a freely aliasable pointer type.
+    /// Returns `FreelyAliasable(_)` if this place represents a freely aliasable pointer type.
     pub fn freely_aliasable(&self) -> Aliasability {
         // Maybe non-obvious: copied upvars can only be considered
         // non-aliasable in once closures, since any other kind can be
@@ -1453,7 +1453,7 @@ impl<'tcx> cmt_<'tcx> {
                 "static item".to_string()
             }
             Categorization::Rvalue(..) => {
-                "non-lvalue".to_string()
+                "non-place".to_string()
             }
             Categorization::Local(vid) => {
                 if tcx.hir.is_argument(vid) {

src/librustc/middle/region.rs

@@ -1112,7 +1112,7 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
     //    I mean that creating a binding into a ref-counted or managed value
     //    would still count.)
     //
-    // 3. `ET`, which matches both rvalues like `foo()` as well as lvalues
+    // 3. `ET`, which matches both rvalues like `foo()` as well as places
     //    based on rvalues like `foo().x[2].y`.
     //
     // A subexpression `<rvalue>` that appears in a let initializer
@@ -1283,7 +1283,7 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
     ///        | (ET)
     ///        | <rvalue>
     ///
-    /// Note: ET is intended to match "rvalues or lvalues based on rvalues".
+    /// Note: ET is intended to match "rvalues or places based on rvalues".
     fn record_rvalue_scope<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
                                      expr: &hir::Expr,
                                      blk_scope: Option<Scope>) {

src/librustc/mir/mod.rs

@@ -733,29 +733,29 @@ pub enum TerminatorKind<'tcx> {
     },
 
     /// Drop the Place and assign the new value over it. This ensures
-    /// that the assignment to LV occurs *even if* the destructor for
+    /// that the assignment to `P` occurs *even if* the destructor for
     /// place unwinds. Its semantics are best explained by by the
     /// elaboration:
     ///
     /// ```
     /// BB0 {
-    ///   DropAndReplace(LV <- RV, goto BB1, unwind BB2)
+    ///   DropAndReplace(P <- V, goto BB1, unwind BB2)
     /// }
     /// ```
     ///
     /// becomes
     ///
     /// ```
     /// BB0 {
-    ///   Drop(LV, goto BB1, unwind BB2)
+    ///   Drop(P, goto BB1, unwind BB2)
     /// }
     /// BB1 {
-    ///   // LV is now unitialized
-    ///   LV <- RV
+    ///   // P is now unitialized
+    ///   P <- V
     /// }
     /// BB2 {
-    ///   // LV is now unitialized -- its dtor panicked
-    ///   LV <- RV
+    ///   // P is now unitialized -- its dtor panicked
+    ///   P <- V
     /// }
     /// ```
     DropAndReplace {

src/librustc/mir/tcx.rs

@@ -52,7 +52,7 @@ impl<'a, 'gcx, 'tcx> PlaceTy<'tcx> {
         match *elem {
             ProjectionElem::Deref => {
                 let ty = self.to_ty(tcx)
-                             .builtin_deref(true, ty::LvaluePreference::NoPreference)
+                             .builtin_deref(true)
                              .unwrap_or_else(|| {
                                  bug!("deref projection of non-dereferencable ty {:?}", self)
                              })

src/librustc/ty/adjustment.rs

@@ -77,7 +77,7 @@ pub enum Adjust<'tcx> {
     /// Go from a mut raw pointer to a const raw pointer.
     MutToConstPointer,
 
-    /// Dereference once, producing an lvalue.
+    /// Dereference once, producing a place.
     Deref(Option<OverloadedDeref<'tcx>>),
 
     /// Take the address and produce either a `&` or `*` pointer.