Move rvalue checking to MIR

Fixes #41139.

Author: arielb1

src/librustc_driver/driver.rs

@@ -35,7 +35,7 @@ use rustc_typeck as typeck;
 use rustc_privacy;
 use rustc_plugin::registry::Registry;
 use rustc_plugin as plugin;
-use rustc_passes::{ast_validation, no_asm, loops, consts, rvalues,
+use rustc_passes::{ast_validation, no_asm, loops, consts,
                    static_recursion, hir_stats, mir_stats};
 use rustc_const_eval::check_match;
 use super::Compilation;
@@ -957,10 +957,6 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
              "liveness checking",
              || middle::liveness::check_crate(tcx));
 
-        time(time_passes,
-             "rvalue checking",
-             || rvalues::check_crate(tcx));
-
         time(time_passes,
              "MIR dump",
              || mir::mir_map::build_mir_for_crate(tcx));
@@ -976,8 +972,8 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
             // in stage 4 below.
             passes.push_hook(box mir::transform::dump_mir::DumpMir);
             passes.push_pass(box mir::transform::simplify::SimplifyCfg::new("initial"));
-            passes.push_pass(box mir::transform::qualify_consts::QualifyAndPromoteConstants);
             passes.push_pass(box mir::transform::type_check::TypeckMir);
+            passes.push_pass(box mir::transform::qualify_consts::QualifyAndPromoteConstants);
             passes.push_pass(
                 box mir::transform::simplify_branches::SimplifyBranches::new("initial"));
             passes.push_pass(box mir::transform::simplify::SimplifyCfg::new("qualify-consts"));

src/librustc_mir/diagnostics.rs

@@ -244,6 +244,39 @@ let baz: bool = { (&FOO as *const i32) == (&BAR as *const i32) };
 ```
 "##,
 
+E0161: r##"
+A value was moved. However, its size was not known at compile time, and only
+values of a known size can be moved.
+
+Erroneous code example:
+
+```compile_fail
+#![feature(box_syntax)]
+
+fn main() {
+    let array: &[isize] = &[1, 2, 3];
+    let _x: Box<[isize]> = box *array;
+    // error: cannot move a value of type [isize]: the size of [isize] cannot
+    //        be statically determined
+}
+```
+
+In Rust, you can only move a value when its size is known at compile time.
+
+To work around this restriction, consider "hiding" the value behind a reference:
+either `&x` or `&mut x`. Since a reference has a fixed size, this lets you move
+it around as usual. Example:
+
+```
+#![feature(box_syntax)]
+
+fn main() {
+    let array: &[isize] = &[1, 2, 3];
+    let _x: Box<&[isize]> = box array; // ok!
+}
+```
+"##,
+
 E0396: r##"
 The value behind a raw pointer can't be determined at compile-time
 (or even link-time), which means it can't be used in a constant

src/librustc_mir/transform/type_check.rs

@@ -24,6 +24,7 @@ use std::fmt;
 use syntax::ast;
 use syntax_pos::{Span, DUMMY_SP};
 
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::indexed_vec::Idx;
 
 fn mirbug(tcx: TyCtxt, span: Span, msg: &str) {
@@ -87,6 +88,11 @@ impl<'a, 'b, 'gcx, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'gcx, 'tcx> {
         self.sanitize_type(rvalue, rval_ty);
     }
 
+    fn visit_local_decl(&mut self, local_decl: &LocalDecl<'tcx>) {
+        self.super_local_decl(local_decl);
+        self.sanitize_type(local_decl, local_decl.ty);
+    }
+
     fn visit_mir(&mut self, mir: &Mir<'tcx>) {
         self.sanitize_type(&"return type", mir.return_ty);
         for local_decl in &mir.local_decls {
@@ -317,6 +323,7 @@ pub struct TypeChecker<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     fulfillment_cx: traits::FulfillmentContext<'tcx>,
     last_span: Span,
     body_id: ast::NodeId,
+    reported_errors: FxHashSet<(Ty<'tcx>, Span)>,
 }
 
 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
@@ -326,6 +333,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
             fulfillment_cx: traits::FulfillmentContext::new(),
             last_span: DUMMY_SP,
             body_id: body_id,
+            reported_errors: FxHashSet(),
         }
     }
 
@@ -641,9 +649,39 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
         }
     }
 
-    fn typeck_mir(&mut self, mir: &Mir<'tcx>) {
+    fn check_local(&mut self, mir: &Mir<'gcx>, local: Local, local_decl: &LocalDecl<'gcx>) {
+        match mir.local_kind(local) {
+            LocalKind::ReturnPointer | LocalKind::Arg => {
+                // return values of normal functions are required to be
+                // sized by typeck, but return values of ADT constructors are
+                // not because we don't include a `Self: Sized` bounds on them.
+                //
+                // Unbound parts of arguments were never required to be Sized
+                // - maybe we should make that a warning.
+                return
+            }
+            LocalKind::Var | LocalKind::Temp => {}
+        }
+
+        let span = local_decl.source_info.span;
+        let ty = local_decl.ty;
+        if !ty.is_sized(self.tcx().global_tcx(), self.infcx.param_env(), span) {
+            if let None = self.reported_errors.replace((ty, span)) {
+                span_err!(self.tcx().sess, span, E0161,
+                          "cannot move a value of type {0}: the size of {0} \
+                           cannot be statically determined", ty);
+            }
+        }
+    }
+
+    fn typeck_mir(&mut self, mir: &Mir<'gcx>) {
         self.last_span = mir.span;
         debug!("run_on_mir: {:?}", mir.span);
+
+        for (local, local_decl) in mir.local_decls.iter_enumerated() {
+            self.check_local(mir, local, local_decl);
+        }
+
         for block in mir.basic_blocks() {
             for stmt in &block.statements {
                 if stmt.source_info.span != DUMMY_SP {
@@ -698,16 +736,18 @@ impl TypeckMir {
 impl<'tcx> MirPass<'tcx> for TypeckMir {
     fn run_pass<'a>(&mut self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                     src: MirSource, mir: &mut Mir<'tcx>) {
-        debug!("run_pass: {}", tcx.node_path_str(src.item_id()));
+        let item_id = src.item_id();
+        let def_id = tcx.hir.local_def_id(item_id);
+        debug!("run_pass: {}", tcx.item_path_str(def_id));
 
         if tcx.sess.err_count() > 0 {
             // compiling a broken program can obviously result in a
             // broken MIR, so try not to report duplicate errors.
             return;
         }
-        let param_env = ty::ParameterEnvironment::for_item(tcx, src.item_id());
+        let param_env = ty::ParameterEnvironment::for_item(tcx, item_id);
         tcx.infer_ctxt(param_env, Reveal::UserFacing).enter(|infcx| {
-            let mut checker = TypeChecker::new(&infcx, src.item_id());
+            let mut checker = TypeChecker::new(&infcx, item_id);
             {
                 let mut verifier = TypeVerifier::new(&mut checker, mir);
                 verifier.visit_mir(mir);

src/librustc_passes/diagnostics.rs

@@ -82,39 +82,6 @@ extern {
 ```
 "##,
 
-E0161: r##"
-A value was moved. However, its size was not known at compile time, and only
-values of a known size can be moved.
-
-Erroneous code example:
-
-```compile_fail
-#![feature(box_syntax)]
-
-fn main() {
-    let array: &[isize] = &[1, 2, 3];
-    let _x: Box<[isize]> = box *array;
-    // error: cannot move a value of type [isize]: the size of [isize] cannot
-    //        be statically determined
-}
-```
-
-In Rust, you can only move a value when its size is known at compile time.
-
-To work around this restriction, consider "hiding" the value behind a reference:
-either `&x` or `&mut x`. Since a reference has a fixed size, this lets you move
-it around as usual. Example:
-
-```
-#![feature(box_syntax)]
-
-fn main() {
-    let array: &[isize] = &[1, 2, 3];
-    let _x: Box<&[isize]> = box array; // ok!
-}
-```
-"##,
-
 E0265: r##"
 This error indicates that a static or constant references itself.
 All statics and constants need to resolve to a value in an acyclic manner.

src/librustc_passes/lib.rs

@@ -47,5 +47,4 @@ pub mod hir_stats;
 pub mod loops;
 pub mod mir_stats;
 pub mod no_asm;
-pub mod rvalues;
 pub mod static_recursion;

src/librustc_passes/rvalues.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+trait Trait {}
+
+fn get_function<'a>() -> &'a Fn() -> Trait { panic!("") }
+
+fn main() {
+    let t : &Trait = &get_function()();
+    //~^ ERROR cannot move a value of type Trait + 'static
+}