From 8e32dade71ad57978786537ec41c13222fd14611 Mon Sep 17 00:00:00 2001
From: bohan <bohan-zhang@foxmail.com>
Date: Sun, 30 Jul 2023 15:49:33 +0800
Subject: [PATCH] parser: more friendly hints for handling `async move` in the
 2015 edition

---
 compiler/rustc_parse/messages.ftl              |  2 ++
 compiler/rustc_parse/src/errors.rs             |  7 +++++++
 compiler/rustc_parse/src/parser/diagnostics.rs | 15 +++++++++++----
 tests/ui/parser/issues/issue-114219.rs         |  4 ++++
 tests/ui/parser/issues/issue-114219.stderr     |  8 ++++++++
 5 files changed, 32 insertions(+), 4 deletions(-)
 create mode 100644 tests/ui/parser/issues/issue-114219.rs
 create mode 100644 tests/ui/parser/issues/issue-114219.stderr

diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 83d96ad8e76..aec27060fed 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -23,6 +23,8 @@ parse_async_block_in_2015 = `async` blocks are only allowed in Rust 2018 or late
 parse_async_fn_in_2015 = `async fn` is not permitted in Rust 2015
     .label = to use `async fn`, switch to Rust 2018 or later
 
+parse_async_move_block_in_2015 = `async move` blocks are only allowed in Rust 2018 or later
+
 parse_async_move_order_incorrect = the order of `move` and `async` is incorrect
     .suggestion = try switching the order
 
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 06c09960727..8ac30a6a5fe 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -1434,6 +1434,13 @@ pub(crate) struct AsyncBlockIn2015 {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_async_move_block_in_2015)]
+pub(crate) struct AsyncMoveBlockIn2015 {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(parse_self_argument_pointer)]
 pub(crate) struct SelfArgumentPointer {
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index e6de51a673c..6156ebec230 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -4,10 +4,11 @@
     TokenExpectType, TokenType,
 };
 use crate::errors::{
-    AmbiguousPlus, AttributeOnParamType, BadQPathStage2, BadTypePlus, BadTypePlusSub, ColonAsSemi,
-    ComparisonOperatorsCannotBeChained, ComparisonOperatorsCannotBeChainedSugg,
-    ConstGenericWithoutBraces, ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything,
-    DocCommentOnParamType, DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
+    AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, BadQPathStage2, BadTypePlus,
+    BadTypePlusSub, ColonAsSemi, ComparisonOperatorsCannotBeChained,
+    ComparisonOperatorsCannotBeChainedSugg, ConstGenericWithoutBraces,
+    ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything, DocCommentOnParamType,
+    DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
     GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg,
     HelpIdentifierStartsWithNumber, InInTypo, IncorrectAwait, IncorrectSemicolon,
     IncorrectUseOfAwait, ParenthesesInForHead, ParenthesesInForHeadSugg,
@@ -573,6 +574,12 @@ fn is_ident_eq_keyword(found: &TokenKind, expected: &TokenType) -> bool {
             return Err(self.sess.create_err(UseEqInstead { span: self.token.span }));
         }
 
+        if self.token.is_keyword(kw::Move) && self.prev_token.is_keyword(kw::Async) {
+            // The 2015 edition is in use because parsing of `async move` has failed.
+            let span = self.prev_token.span.to(self.token.span);
+            return Err(self.sess.create_err(AsyncMoveBlockIn2015 { span }));
+        }
+
         let expect = tokens_to_string(&expected);
         let actual = super::token_descr(&self.token);
         let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
diff --git a/tests/ui/parser/issues/issue-114219.rs b/tests/ui/parser/issues/issue-114219.rs
new file mode 100644
index 00000000000..332258b628c
--- /dev/null
+++ b/tests/ui/parser/issues/issue-114219.rs
@@ -0,0 +1,4 @@
+fn main() {
+    async move {};
+    //~^ ERROR `async move` blocks are only allowed in Rust 2018 or later
+}
diff --git a/tests/ui/parser/issues/issue-114219.stderr b/tests/ui/parser/issues/issue-114219.stderr
new file mode 100644
index 00000000000..90dcdc42775
--- /dev/null
+++ b/tests/ui/parser/issues/issue-114219.stderr
@@ -0,0 +1,8 @@
+error: `async move` blocks are only allowed in Rust 2018 or later
+  --> $DIR/issue-114219.rs:2:5
+   |
+LL |     async move {};
+   |     ^^^^^^^^^^
+
+error: aborting due to previous error
+