Rollup merge of rust-lang#66264 - guanqun:fix-mbe-missing-close-delim, r=estebank

fix an ICE in macro's diagnostic message

This has two small fixes:
1. for the left brace, we don't need `<space>{`, simply `{` is enough.
2. for the right brace, it tries to peel off one character even when the close delim is missing. Without this fix, it would crash in some cases. (as shown in the new test case)

r? @estebank

Author: JohnTitor

src/librustc_parse/parser/item.rs

@@ -1742,14 +1742,25 @@ impl<'a> Parser<'a> {
     }
 
     fn report_invalid_macro_expansion_item(&self) {
+        let has_close_delim = self.sess.source_map()
+            .span_to_snippet(self.prev_span)
+            .map(|s| s.ends_with(")") || s.ends_with("]"))
+            .unwrap_or(false);
+        let right_brace_span = if has_close_delim {
+            // it's safe to peel off one character only when it has the close delim
+            self.prev_span.with_lo(self.prev_span.hi() - BytePos(1))
+        } else {
+            self.sess.source_map().next_point(self.prev_span)
+        };
+
         self.struct_span_err(
             self.prev_span,
             "macros that expand to items must be delimited with braces or followed by a semicolon",
         ).multipart_suggestion(
             "change the delimiters to curly braces",
             vec![
-                (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
-                (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
+                (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), "{".to_string()),
+                (right_brace_span, '}'.to_string()),
             ],
             Applicability::MaybeIncorrect,
         ).span_suggestion(

src/test/ui/parser/macros-no-semicolon-items.stderr

@@ -6,8 +6,8 @@ LL | macro_rules! foo()
    |
 help: change the delimiters to curly braces
    |
-LL | macro_rules! foo {}
-   |                  ^^
+LL | macro_rules! foo{}
+   |                 ^^
 help: add a semicolon
    |
 LL | macro_rules! foo();
@@ -26,7 +26,7 @@ LL | | )
    |
 help: change the delimiters to curly braces
    |
-LL | bar! {
+LL | bar!{
 LL |     blah
 LL |     blah
 LL |     blah

src/test/ui/parser/mbe_missing_right_paren.rs

@@ -0,0 +1,3 @@
+// ignore-tidy-trailing-newlines
+// error-pattern: aborting due to 3 previous errors
+macro_rules! abc(ؼ

src/test/ui/parser/mbe_missing_right_paren.stderr

@@ -0,0 +1,31 @@
+error: this file contains an un-closed delimiter
+  --> $DIR/mbe_missing_right_paren.rs:3:19
+   |
+LL | macro_rules! abc(ؼ
+   |                 - ^
+   |                 |
+   |                 un-closed delimiter
+
+error: macros that expand to items must be delimited with braces or followed by a semicolon
+  --> $DIR/mbe_missing_right_paren.rs:3:17
+   |
+LL | macro_rules! abc(ؼ
+   |                 ^^
+   |
+help: change the delimiters to curly braces
+   |
+LL | macro_rules! abc{ؼ}
+   |                 ^ ^
+help: add a semicolon
+   |
+LL | macro_rules! abc(ؼ;
+   |                   ^
+
+error: unexpected end of macro invocation
+  --> $DIR/mbe_missing_right_paren.rs:3:1
+   |
+LL | macro_rules! abc(ؼ
+   | ^^^^^^^^^^^^^^^^^^ missing tokens in macro arguments
+
+error: aborting due to 3 previous errors
+