From 1cc42ea6750affbef2bca699bde30ac321e15939 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Fri, 24 May 2019 19:30:25 -0700
Subject: [PATCH] Add support for suggesting as_ref to Result accesses

---
 src/librustc_mir/borrow_check/move_errors.rs   | 10 ++++++++--
 .../ui/suggestions/option-content-move.fixed   | 18 ++++++++++++++++++
 src/test/ui/suggestions/option-content-move.rs | 18 ++++++++++++++++++
 .../ui/suggestions/option-content-move.stderr  | 11 ++++++++++-
 4 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/src/librustc_mir/borrow_check/move_errors.rs b/src/librustc_mir/borrow_check/move_errors.rs
index 19ad92a8275f..f060e1931829 100644
--- a/src/librustc_mir/borrow_check/move_errors.rs
+++ b/src/librustc_mir/borrow_check/move_errors.rs
@@ -319,10 +319,16 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
                         original_path.ty(self.mir, self.infcx.tcx).ty,
                     );
                     let snippet = self.infcx.tcx.sess.source_map().span_to_snippet(span).unwrap();
-                    if orig_path_ty.starts_with("std::option::Option") {
+                    let is_option = orig_path_ty.starts_with("std::option::Option");
+                    let is_result = orig_path_ty.starts_with("std::result::Result");
+                    if  is_option || is_result {
                         err.span_suggestion(
                             span,
-                            "consider borrowing the `Option`'s content",
+                            &format!("consider borrowing the `{}`'s content", if is_option {
+                                "Option"
+                            } else {
+                                "Result"
+                            }),
                             format!("{}.as_ref()", snippet),
                             Applicability::MaybeIncorrect,
                         );
diff --git a/src/test/ui/suggestions/option-content-move.fixed b/src/test/ui/suggestions/option-content-move.fixed
index 7113de9f4148..f163cd104ffa 100644
--- a/src/test/ui/suggestions/option-content-move.fixed
+++ b/src/test/ui/suggestions/option-content-move.fixed
@@ -18,4 +18,22 @@ impl LipogramCorpora {
     }
 }
 
+pub struct LipogramCorpora2 {
+    selections: Vec<(char, Result<String, String>)>,
+}
+
+impl LipogramCorpora2 {
+    pub fn validate_all(&mut self) -> Result<(), char> {
+        for selection in &self.selections {
+            if selection.1.is_ok() {
+                if selection.1.as_ref().unwrap().contains(selection.0) {
+                //~^ ERROR cannot move out of borrowed content
+                    return Err(selection.0);
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
 fn main() {}
diff --git a/src/test/ui/suggestions/option-content-move.rs b/src/test/ui/suggestions/option-content-move.rs
index 5a38376ffa60..350486a802d3 100644
--- a/src/test/ui/suggestions/option-content-move.rs
+++ b/src/test/ui/suggestions/option-content-move.rs
@@ -18,4 +18,22 @@ impl LipogramCorpora {
     }
 }
 
+pub struct LipogramCorpora2 {
+    selections: Vec<(char, Result<String, String>)>,
+}
+
+impl LipogramCorpora2 {
+    pub fn validate_all(&mut self) -> Result<(), char> {
+        for selection in &self.selections {
+            if selection.1.is_ok() {
+                if selection.1.unwrap().contains(selection.0) {
+                //~^ ERROR cannot move out of borrowed content
+                    return Err(selection.0);
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
 fn main() {}
diff --git a/src/test/ui/suggestions/option-content-move.stderr b/src/test/ui/suggestions/option-content-move.stderr
index 7f019c3b5b92..0a325ac54eaf 100644
--- a/src/test/ui/suggestions/option-content-move.stderr
+++ b/src/test/ui/suggestions/option-content-move.stderr
@@ -7,6 +7,15 @@ LL |                 if selection.1.unwrap().contains(selection.0) {
    |                    cannot move out of borrowed content
    |                    help: consider borrowing the `Option`'s content: `selection.1.as_ref()`
 
-error: aborting due to previous error
+error[E0507]: cannot move out of borrowed content
+  --> $DIR/option-content-move.rs:29:20
+   |
+LL |                 if selection.1.unwrap().contains(selection.0) {
+   |                    ^^^^^^^^^^^
+   |                    |
+   |                    cannot move out of borrowed content
+   |                    help: consider borrowing the `Result`'s content: `selection.1.as_ref()`
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0507`.