From a8421cacfec5798f600549508545b85003c2143c Mon Sep 17 00:00:00 2001
From: Fabian Wolff <fabian.wolff@alumni.ethz.ch>
Date: Fri, 10 Sep 2021 22:33:44 +0200
Subject: [PATCH] Fix error recovery in format macro parsing

---
 compiler/rustc_builtin_macros/src/format.rs   | 31 +++++----
 .../rustc_parse/src/parser/diagnostics.rs     |  4 +-
 src/test/ui/parser/issue-88770.rs             | 11 ++++
 src/test/ui/parser/issue-88770.stderr         | 66 +++++++++++++++++++
 4 files changed, 94 insertions(+), 18 deletions(-)
 create mode 100644 src/test/ui/parser/issue-88770.rs
 create mode 100644 src/test/ui/parser/issue-88770.stderr

diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 8508b3b7ae6ed..cbed1bb850c42 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -164,23 +164,22 @@ fn parse_args<'a>(
                 p.clear_expected_tokens();
             }
 
-            // `Parser::expect` tries to recover using the
-            // `Parser::unexpected_try_recover` function. This function is able
-            // to recover if the expected token is a closing delimiter.
-            //
-            // As `,` is not a closing delimiter, it will always return an `Err`
-            // variant.
-            let mut err = p.expect(&token::Comma).unwrap_err();
-
-            match token::TokenKind::Comma.similar_tokens() {
-                Some(tks) if tks.contains(&p.token.kind) => {
-                    // If a similar token is found, then it may be a typo. We
-                    // consider it as a comma, and continue parsing.
-                    err.emit();
-                    p.bump();
+            match p.expect(&token::Comma) {
+                Err(mut err) => {
+                    match token::TokenKind::Comma.similar_tokens() {
+                        Some(tks) if tks.contains(&p.token.kind) => {
+                            // If a similar token is found, then it may be a typo. We
+                            // consider it as a comma, and continue parsing.
+                            err.emit();
+                            p.bump();
+                        }
+                        // Otherwise stop the parsing and return the error.
+                        _ => return Err(err),
+                    }
+                }
+                Ok(recovered) => {
+                    assert!(recovered);
                 }
-                // Otherwise stop the parsing and return the error.
-                _ => return Err(err),
             }
         }
         first = false;
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 94ca70d3f9578..c2db5a027054c 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -277,7 +277,7 @@ impl<'a> Parser<'a> {
                 self.struct_span_err(sp, &msg)
                     .span_suggestion_short(sp, "change this to `;`", ";".to_string(), appl)
                     .emit();
-                return Ok(false);
+                return Ok(true);
             } else if self.look_ahead(0, |t| {
                 t == &token::CloseDelim(token::Brace)
                     || (
@@ -295,7 +295,7 @@ impl<'a> Parser<'a> {
                     .span_label(self.token.span, "unexpected token")
                     .span_suggestion_short(sp, "add `;` here", ";".to_string(), appl)
                     .emit();
-                return Ok(false);
+                return Ok(true);
             }
         }
 
diff --git a/src/test/ui/parser/issue-88770.rs b/src/test/ui/parser/issue-88770.rs
new file mode 100644
index 0000000000000..bf89033f560e9
--- /dev/null
+++ b/src/test/ui/parser/issue-88770.rs
@@ -0,0 +1,11 @@
+// Regression test for the ICE described in #88770.
+
+// error-pattern:this file contains an unclosed delimiter
+// error-pattern:expected one of
+// error-pattern:missing `in` in `for` loop
+// error-pattern:expected `;`, found `e`
+
+fn m(){print!("",(c for&g
+u
+e
+e
diff --git a/src/test/ui/parser/issue-88770.stderr b/src/test/ui/parser/issue-88770.stderr
new file mode 100644
index 0000000000000..c7e24155d1692
--- /dev/null
+++ b/src/test/ui/parser/issue-88770.stderr
@@ -0,0 +1,66 @@
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-88770.rs:11:3
+   |
+LL | fn m(){print!("",(c for&g
+   |       -      -   - unclosed delimiter
+   |       |      |
+   |       |      unclosed delimiter
+   |       unclosed delimiter
+...
+LL | e
+   |   ^
+
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-88770.rs:11:3
+   |
+LL | fn m(){print!("",(c for&g
+   |       -      -   - unclosed delimiter
+   |       |      |
+   |       |      unclosed delimiter
+   |       unclosed delimiter
+...
+LL | e
+   |   ^
+
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-88770.rs:11:3
+   |
+LL | fn m(){print!("",(c for&g
+   |       -      -   - unclosed delimiter
+   |       |      |
+   |       |      unclosed delimiter
+   |       unclosed delimiter
+...
+LL | e
+   |   ^
+
+error: missing `in` in `for` loop
+  --> $DIR/issue-88770.rs:8:26
+   |
+LL |   fn m(){print!("",(c for&g
+   |  __________________________^
+LL | | u
+   | |_ help: try adding `in` here
+
+error: expected one of `!`, `)`, `,`, `.`, `::`, `?`, `{`, or an operator, found keyword `for`
+  --> $DIR/issue-88770.rs:8:21
+   |
+LL | fn m(){print!("",(c for&g
+   |                     ^^^ expected one of 8 possible tokens
+
+error: expected `;`, found `e`
+  --> $DIR/issue-88770.rs:10:2
+   |
+LL | e
+   |  ^ help: add `;` here
+LL | e
+   | - unexpected token
+
+error: expected one of `!`, `,`, `.`, `::`, `?`, `{`, or an operator, found `)`
+  --> $DIR/issue-88770.rs:11:3
+   |
+LL | e
+   |   ^ expected one of 7 possible tokens
+
+error: aborting due to 7 previous errors
+