From 0959f0f912c1029f0dfd3de431786433211a1f2d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Tue, 26 Jan 2021 11:24:43 -0800
Subject: [PATCH] Tweak suggestion for missing field in patterns

Account for parser recovered struct and tuple patterns to avoid invalid
suggestion.

Follow up to #81103.
---
 compiler/rustc_typeck/src/check/pat.rs        | 25 ++++++-------------
 .../struct_destructure_fail.stderr            |  8 +++---
 src/test/ui/error-codes/E0027.stderr          | 12 ++++-----
 .../structs/struct-pat-derived-error.stderr   |  4 +--
 4 files changed, 19 insertions(+), 30 deletions(-)

diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs
index 79234f076acd1..1c1f7f7886fcd 100644
--- a/compiler/rustc_typeck/src/check/pat.rs
+++ b/compiler/rustc_typeck/src/check/pat.rs
@@ -1525,24 +1525,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 _ => return err,
             },
             [.., field] => {
-                // if last field has a trailing comma, use the comma
-                // as the span to avoid trailing comma in ultimate
-                // suggestion (Issue #78511)
-                let tail = field.span.shrink_to_hi().until(pat.span.shrink_to_hi());
-                let tail_through_comma = self.tcx.sess.source_map().span_through_char(tail, ',');
-                let sp = if tail_through_comma == tail {
-                    field.span.shrink_to_hi()
-                } else {
-                    tail_through_comma
-                };
-                (
-                    match pat.kind {
-                        PatKind::Struct(_, [_, ..], _) => ", ",
-                        _ => "",
-                    },
-                    "",
-                    sp,
-                )
+                // Account for last field having a trailing comma or parse recovery at the tail of
+                // the pattern to avoid invalid suggestion (#78511).
+                let tail = field.span.shrink_to_hi().with_hi(pat.span.hi());
+                match &pat.kind {
+                    PatKind::Struct(..) => (", ", " }", tail),
+                    _ => return err,
+                }
             }
         };
         err.span_suggestion(
diff --git a/src/test/ui/destructuring-assignment/struct_destructure_fail.stderr b/src/test/ui/destructuring-assignment/struct_destructure_fail.stderr
index c0955ef8b065a..8a83e145ea2d0 100644
--- a/src/test/ui/destructuring-assignment/struct_destructure_fail.stderr
+++ b/src/test/ui/destructuring-assignment/struct_destructure_fail.stderr
@@ -32,12 +32,12 @@ LL |     Struct { a, _ } = Struct { a: 1, b: 2 };
    |
 help: include the missing field in the pattern
    |
-LL |     Struct { a, b _ } = Struct { a: 1, b: 2 };
-   |               ^^^
+LL |     Struct { a, b } = Struct { a: 1, b: 2 };
+   |               ^^^^^
 help: if you don't care about this missing field, you can explicitly ignore it
    |
-LL |     Struct { a, .. _ } = Struct { a: 1, b: 2 };
-   |               ^^^^
+LL |     Struct { a, .. } = Struct { a: 1, b: 2 };
+   |               ^^^^^^
 
 error: aborting due to 5 previous errors
 
diff --git a/src/test/ui/error-codes/E0027.stderr b/src/test/ui/error-codes/E0027.stderr
index 694bbc358fee2..a3dd6910be4a5 100644
--- a/src/test/ui/error-codes/E0027.stderr
+++ b/src/test/ui/error-codes/E0027.stderr
@@ -7,11 +7,11 @@ LL |         Dog { age: x } => {}
 help: include the missing field in the pattern
    |
 LL |         Dog { age: x, name } => {}
-   |                     ^^^^^^
+   |                     ^^^^^^^^
 help: if you don't care about this missing field, you can explicitly ignore it
    |
 LL |         Dog { age: x, .. } => {}
-   |                     ^^^^
+   |                     ^^^^^^
 
 error[E0027]: pattern does not mention field `age`
   --> $DIR/E0027.rs:15:9
@@ -22,11 +22,11 @@ LL |         Dog { name: x, } => {}
 help: include the missing field in the pattern
    |
 LL |         Dog { name: x, age } => {}
-   |                      ^^^^^
+   |                      ^^^^^^^
 help: if you don't care about this missing field, you can explicitly ignore it
    |
 LL |         Dog { name: x, .. } => {}
-   |                      ^^^^
+   |                      ^^^^^^
 
 error[E0027]: pattern does not mention field `age`
   --> $DIR/E0027.rs:19:9
@@ -37,11 +37,11 @@ LL |         Dog { name: x  , } => {}
 help: include the missing field in the pattern
    |
 LL |         Dog { name: x, age } => {}
-   |                      ^^^^^
+   |                      ^^^^^^^
 help: if you don't care about this missing field, you can explicitly ignore it
    |
 LL |         Dog { name: x, .. } => {}
-   |                      ^^^^
+   |                      ^^^^^^
 
 error[E0027]: pattern does not mention fields `name`, `age`
   --> $DIR/E0027.rs:22:9
diff --git a/src/test/ui/structs/struct-pat-derived-error.stderr b/src/test/ui/structs/struct-pat-derived-error.stderr
index 921d060faa38b..c1a95636d34cb 100644
--- a/src/test/ui/structs/struct-pat-derived-error.stderr
+++ b/src/test/ui/structs/struct-pat-derived-error.stderr
@@ -19,11 +19,11 @@ LL |         let A { x, y } = self.d;
 help: include the missing fields in the pattern
    |
 LL |         let A { x, y, b, c } = self.d;
-   |                     ^^^^^^
+   |                     ^^^^^^^^
 help: if you don't care about these missing fields, you can explicitly ignore them
    |
 LL |         let A { x, y, .. } = self.d;
-   |                     ^^^^
+   |                     ^^^^^^
 
 error: aborting due to 3 previous errors