From ef6851cdb285d18e54b9770b455b595565572462 Mon Sep 17 00:00:00 2001
From: David Wood <david@davidtw.co>
Date: Thu, 30 Aug 2018 18:14:54 +0200
Subject: [PATCH] Added InitLocation to encode Location or Local depending on
 source of Init

---
 src/librustc_mir/borrow_check/mod.rs          |  4 +++-
 .../borrow_check/mutability_errors.rs         |  1 +
 .../dataflow/move_paths/builder.rs            |  7 +++---
 src/librustc_mir/dataflow/move_paths/mod.rs   | 24 ++++++++++++++++---
 4 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs
index 16d34082642b..b06a1e0e19f6 100644
--- a/src/librustc_mir/borrow_check/mod.rs
+++ b/src/librustc_mir/borrow_check/mod.rs
@@ -1601,7 +1601,9 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         if let Some(&init_index) = first_init_index {
             // And, if so, report an error.
             let init = &self.move_data.inits[init_index];
-            self.report_illegal_reassignment(context, place_span, init.span, place_span.0);
+            self.report_illegal_reassignment(
+                context, place_span, init.span(&self.mir), place_span.0
+            );
         }
     }
 
diff --git a/src/librustc_mir/borrow_check/mutability_errors.rs b/src/librustc_mir/borrow_check/mutability_errors.rs
index f96ef909c0df..645cce8dd793 100644
--- a/src/librustc_mir/borrow_check/mutability_errors.rs
+++ b/src/librustc_mir/borrow_check/mutability_errors.rs
@@ -16,6 +16,7 @@ use rustc::ty::{self, TyCtxt};
 use rustc_data_structures::indexed_vec::Idx;
 use syntax_pos::Span;
 
+use dataflow::move_paths::InitLocation;
 use borrow_check::MirBorrowckCtxt;
 use util::borrowck_errors::{BorrowckErrors, Origin};
 use util::collect_writes::FindAssignments;
diff --git a/src/librustc_mir/dataflow/move_paths/builder.rs b/src/librustc_mir/dataflow/move_paths/builder.rs
index 2148363c7971..0162bb84b94b 100644
--- a/src/librustc_mir/dataflow/move_paths/builder.rs
+++ b/src/librustc_mir/dataflow/move_paths/builder.rs
@@ -20,7 +20,7 @@ use std::mem;
 use super::abs_domain::Lift;
 
 use super::{LocationMap, MoveData, MovePath, MovePathLookup, MovePathIndex, MoveOut, MoveOutIndex};
-use super::{MoveError, InitIndex, Init, LookupResult, InitKind};
+use super::{MoveError, InitIndex, Init, InitLocation, LookupResult, InitKind};
 use super::IllegalMoveOriginKind::*;
 
 struct MoveDataBuilder<'a, 'gcx: 'tcx, 'tcx: 'a> {
@@ -237,10 +237,9 @@ impl<'a, 'gcx, 'tcx> MoveDataBuilder<'a, 'gcx, 'tcx> {
     fn gather_args(&mut self) {
         for arg in self.mir.args_iter() {
             let path = self.data.rev_lookup.locals[arg];
-            let span = self.mir.local_decls[arg].source_info.span;
 
             let init = self.data.inits.push(Init {
-                path, span, kind: InitKind::Deep
+                path, kind: InitKind::Deep, location: InitLocation::Argument(arg),
             });
 
             debug!("gather_args: adding init {:?} of {:?} for argument {:?}",
@@ -428,7 +427,7 @@ impl<'b, 'a, 'gcx, 'tcx> Gatherer<'b, 'a, 'gcx, 'tcx> {
 
         if let LookupResult::Exact(path) = self.builder.data.rev_lookup.find(place) {
             let init = self.builder.data.inits.push(Init {
-                span: self.builder.mir.source_info(self.loc).span,
+                location: InitLocation::Statement(self.loc),
                 path,
                 kind,
             });
diff --git a/src/librustc_mir/dataflow/move_paths/mod.rs b/src/librustc_mir/dataflow/move_paths/mod.rs
index 7b4cbdf7131b..8728afc228fc 100644
--- a/src/librustc_mir/dataflow/move_paths/mod.rs
+++ b/src/librustc_mir/dataflow/move_paths/mod.rs
@@ -196,12 +196,21 @@ impl fmt::Debug for MoveOut {
 pub struct Init {
     /// path being initialized
     pub path: MovePathIndex,
-    /// span of initialization
-    pub span: Span,
+    /// location of initialization
+    pub location: InitLocation,
     /// Extra information about this initialization
     pub kind: InitKind,
 }
 
+
+/// Initializations can be from an argument or from a statement. Arguments
+/// do not have locations, in those cases the `Local` is kept..
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum InitLocation {
+    Argument(Local),
+    Statement(Location),
+}
+
 /// Additional information about the initialization.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum InitKind {
@@ -215,7 +224,16 @@ pub enum InitKind {
 
 impl fmt::Debug for Init {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{:?}@{:?} ({:?})", self.path, self.span, self.kind)
+        write!(fmt, "{:?}@{:?} ({:?})", self.path, self.location, self.kind)
+    }
+}
+
+impl Init {
+    crate fn span<'gcx>(&self, mir: &Mir<'gcx>) -> Span {
+        match self.location {
+            InitLocation::Argument(local) => mir.local_decls[local].source_info.span,
+            InitLocation::Statement(location) => mir.source_info(location).span,
+        }
     }
 }