From 2cc7782cfd85a2c4dc2fa566fae4d4e356976471 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 23 Jun 2023 19:18:18 +0000
Subject: [PATCH] Add suggestion for bad block fragment error

---
 compiler/rustc_parse/messages.ftl             |  1 +
 compiler/rustc_parse/src/errors.rs            | 11 +++++++++++
 compiler/rustc_parse/src/parser/expr.rs       |  4 ++++
 tests/ui/parser/bad-interpolated-block.stderr | 12 ++++++++++++
 tests/ui/parser/labeled-no-colon-expr.stderr  |  4 ++++
 5 files changed, 32 insertions(+)

diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 35eec2c8e1b17..9787d98c1a49a 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -353,6 +353,7 @@ parse_int_literal_too_large = integer literal is too large
 
 parse_invalid_block_macro_segment = cannot use a `block` macro fragment here
     .label = the `block` fragment is within this context
+    .suggestion = wrap this in another block
 
 parse_invalid_char_in_escape = {parse_invalid_char_in_escape_msg}: `{$ch}`
     .label = {parse_invalid_char_in_escape_msg}
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 84494eab855c4..96e1c0e3c6d9e 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -333,6 +333,17 @@ pub(crate) struct InvalidBlockMacroSegment {
     pub span: Span,
     #[label]
     pub context: Span,
+    #[subdiagnostic]
+    pub wrap: WrapInExplicitBlock,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(parse_suggestion, applicability = "machine-applicable")]
+pub(crate) struct WrapInExplicitBlock {
+    #[suggestion_part(code = "{{ ")]
+    pub lo: Span,
+    #[suggestion_part(code = " }}")]
+    pub hi: Span,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 88c6cc1ae7072..1b3d4e301a92a 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -2186,6 +2186,10 @@ impl<'a> Parser<'a> {
             self.sess.emit_err(errors::InvalidBlockMacroSegment {
                 span: self.token.span,
                 context: lo.to(self.token.span),
+                wrap: errors::WrapInExplicitBlock {
+                    lo: self.token.span.shrink_to_lo(),
+                    hi: self.token.span.shrink_to_hi(),
+                },
             });
         }
 
diff --git a/tests/ui/parser/bad-interpolated-block.stderr b/tests/ui/parser/bad-interpolated-block.stderr
index 2a0999afdfaf8..651036c51c948 100644
--- a/tests/ui/parser/bad-interpolated-block.stderr
+++ b/tests/ui/parser/bad-interpolated-block.stderr
@@ -10,6 +10,10 @@ LL |     m!({});
    |     ------ in this macro invocation
    |
    = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: wrap this in another block
+   |
+LL |         'lab: { $b };
+   |               +    +
 
 error: cannot use a `block` macro fragment here
   --> $DIR/bad-interpolated-block.rs:6:16
@@ -23,6 +27,10 @@ LL |     m!({});
    |     ------ in this macro invocation
    |
    = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: wrap this in another block
+   |
+LL |         unsafe { $b };
+   |                +    +
 
 error: cannot use a `block` macro fragment here
   --> $DIR/bad-interpolated-block.rs:7:23
@@ -34,6 +42,10 @@ LL |     m!({});
    |     ------ in this macro invocation
    |
    = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: wrap this in another block
+   |
+LL |         |x: u8| -> () { $b };
+   |                       +    +
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/parser/labeled-no-colon-expr.stderr b/tests/ui/parser/labeled-no-colon-expr.stderr
index 62288fe152da3..4d61d9c14034c 100644
--- a/tests/ui/parser/labeled-no-colon-expr.stderr
+++ b/tests/ui/parser/labeled-no-colon-expr.stderr
@@ -77,6 +77,10 @@ LL |     m!({});
    |     ------ in this macro invocation
    |
    = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: wrap this in another block
+   |
+LL |             'l5 { $b };
+   |                 +    +
 
 error: labeled expression must be followed by `:`
   --> $DIR/labeled-no-colon-expr.rs:14:8