Auto merge of #76598 - ad-anssi:diagnostic_errors_fix, r=estebank

Fixing memory exhaustion when formatting short code suggestion

Details can be found in issue #76597. This PR replaces substractions with `saturating_sub`'s to avoid usize wrapping leading to memory exhaustion when formatting short suggestion messages.

compiler/rustc_errors/src/emitter.rs

@@ -959,15 +959,15 @@ impl EmitterWriter {
                         '_',
                         line_offset + pos,
                         width_offset + depth,
-                        code_offset + annotation.start_col - left,
+                        (code_offset + annotation.start_col).saturating_sub(left),
                         style,
                     );
                 }
                 _ if self.teach => {
                     buffer.set_style_range(
                         line_offset,
-                        code_offset + annotation.start_col - left,
-                        code_offset + annotation.end_col - left,
+                        (code_offset + annotation.start_col).saturating_sub(left),
+                        (code_offset + annotation.end_col).saturating_sub(left),
                         style,
                         annotation.is_primary,
                     );

compiler/rustc_parse/src/parser/mod.rs

@@ -694,9 +694,13 @@ impl<'a> Parser<'a> {
                                 Ok(t) => {
                                     // Parsed successfully, therefore most probably the code only
                                     // misses a separator.
+                                    let mut exp_span = self.sess.source_map().next_point(sp);
+                                    if self.sess.source_map().is_multiline(exp_span) {
+                                        exp_span = sp;
+                                    }
                                     expect_err
                                         .span_suggestion_short(
-                                            self.sess.source_map().next_point(sp),
+                                            exp_span,
                                             &format!("missing `{}`", token_str),
                                             token_str,
                                             Applicability::MaybeIncorrect,

src/test/ui/issue-76597.fixed

@@ -0,0 +1,11 @@
+// run-rustfix
+
+#![allow(dead_code)]
+#![allow(unused_variables)]
+fn f(
+                                     x: u8,
+                                     y: u8,
+) {}
+//~^^ ERROR: expected one of `!`, `(`, `)`, `+`, `,`, `::`, or `<`, found `y`
+
+fn main() {}

src/test/ui/issue-76597.rs

@@ -0,0 +1,11 @@
+// run-rustfix
+
+#![allow(dead_code)]
+#![allow(unused_variables)]
+fn f(
+                                     x: u8
+                                     y: u8,
+) {}
+//~^^ ERROR: expected one of `!`, `(`, `)`, `+`, `,`, `::`, or `<`, found `y`
+
+fn main() {}

src/test/ui/issue-76597.stderr

@@ -0,0 +1,13 @@
+error: expected one of `!`, `(`, `)`, `+`, `,`, `::`, or `<`, found `y`
+  --> $DIR/issue-76597.rs:7:38
+   |
+LL | ...                   x: u8
+   |                            -
+   |                            |
+   |                            expected one of 7 possible tokens
+   |                            help: missing `,`
+LL | ...                   y: u8,
+   |                       ^ unexpected token
+
+error: aborting due to previous error
+