rustc_parse_format: introduce `peek` and `peek_ahead`

1 files changed, 36 insertions, 28 deletions

diff --git a/compiler/rustc_parse_format/src/lib.rs b/compiler/rustc_parse_format/src/lib.rs
index 9dd064aca66..358723a17ef 100644
--- a/compiler/rustc_parse_format/src/lib.rs
+++ b/compiler/rustc_parse_format/src/lib.rs
@@ -241,11 +241,11 @@ impl<'a> Iterator for Parser<'a> {
     type Item = Piece<'a>;
 
     fn next(&mut self) -> Option<Piece<'a>> {
-        if let Some(&(Range { start, end }, idx, ch)) = self.input_vec.get(self.input_vec_index) {
+        if let Some((Range { start, end }, idx, ch)) = self.peek() {
             match ch {
                 '{' => {
                     self.input_vec_index += 1;
-                    if let Some(&(_, i, '{')) = self.input_vec.get(self.input_vec_index) {
+                    if let Some((_, i, '{')) = self.peek() {
                         self.input_vec_index += 1;
                         // double open brace escape: "{{"
                         // next state after this is either end-of-input or seen-a-brace
@@ -258,7 +258,7 @@ impl<'a> Iterator for Parser<'a> {
                             if self.is_source_literal {
                                 self.arg_places.push(start..close_brace_range.end);
                             }
-                        } else if let Some(&(_, _, c)) = self.input_vec.get(self.input_vec_index) {
+                        } else if let Some((_, _, c)) = self.peek() {
                             match c {
                                 '?' => self.suggest_format_debug(),
                                 '<' | '^' | '>' => self.suggest_format_align(c),
@@ -272,7 +272,7 @@ impl<'a> Iterator for Parser<'a> {
                 }
                 '}' => {
                     self.input_vec_index += 1;
-                    if let Some(&(_, i, '}')) = self.input_vec.get(self.input_vec_index) {
+                    if let Some((_, i, '}')) = self.peek() {
                         self.input_vec_index += 1;
                         // double close brace escape: "}}"
                         // next state after this is either end-of-input or start
@@ -406,6 +406,16 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Peeks at the current position, without incrementing the pointer.
+    pub fn peek(&self) -> Option<(Range<usize>, usize, char)> {
+        self.input_vec.get(self.input_vec_index).cloned()
+    }
+
+    /// Peeks at the current position + 1, without incrementing the pointer.
+    pub fn peek_ahead(&self) -> Option<(Range<usize>, usize, char)> {
+        self.input_vec.get(self.input_vec_index + 1).cloned()
+    }
+
     /// Optionally consumes the specified character. If the character is not at
     /// the current position, then the current iterator isn't moved and `false` is
     /// returned, otherwise the character is consumed and `true` is returned.
@@ -418,10 +428,10 @@ impl<'a> Parser<'a> {
     /// returned, otherwise the character is consumed and the current position is
     /// returned.
     fn consume_pos(&mut self, ch: char) -> Option<(Range<usize>, usize)> {
-        if let Some((r, i, c)) = self.input_vec.get(self.input_vec_index) {
-            if ch == *c {
+        if let Some((r, i, c)) = self.peek() {
+            if ch == c {
                 self.input_vec_index += 1;
-                return Some((r.clone(), *i));
+                return Some((r, i));
             }
         }
         None
@@ -432,11 +442,10 @@ impl<'a> Parser<'a> {
     fn consume_closing_brace(&mut self, arg: &Argument<'_>) -> Option<Range<usize>> {
         self.ws();
 
-        let (range, description) = if let Some((r, _, c)) = self.input_vec.get(self.input_vec_index)
-        {
-            if *c == '}' {
+        let (range, description) = if let Some((r, _, c)) = self.peek() {
+            if c == '}' {
                 self.input_vec_index += 1;
-                return Some(r.clone());
+                return Some(r);
             }
             // or r.clone()?
             (r.start..r.start, format!("expected `}}`, found `{}`", c.escape_debug()))
@@ -484,10 +493,10 @@ impl<'a> Parser<'a> {
     /// Parses all of a string which is to be considered a "raw literal" in a
     /// format string. This is everything outside of the braces.
     fn string(&mut self, start: usize) -> &'a str {
-        while let Some((r, i, c)) = self.input_vec.get(self.input_vec_index) {
+        while let Some((r, i, c)) = self.peek() {
             match c {
                 '{' | '}' => {
-                    return &self.input[start..*i];
+                    return &self.input[start..i];
                 }
                 '\n' if self.is_source_literal => {
                     self.input_vec_index += 1;
@@ -540,19 +549,18 @@ impl<'a> Parser<'a> {
         if let Some(i) = self.integer() {
             Some(ArgumentIs(i.into()))
         } else {
-            match self.input_vec.get(self.input_vec_index) {
-                Some((range, _, c)) if rustc_lexer::is_id_start(*c) => {
+            match self.peek() {
+                Some((range, _, c)) if rustc_lexer::is_id_start(c) => {
                     let start = range.start;
                     let word = self.word();
 
                     // Recover from `r#ident` in format strings.
                     // FIXME: use a let chain
                     if word == "r" {
-                        if let Some((r, _, '#')) = self.input_vec.get(self.input_vec_index) {
+                        if let Some((r, _, '#')) = self.peek() {
                             if self
-                                .input_vec
-                                .get(self.input_vec_index + 1)
-                                .is_some_and(|(_, _, c)| rustc_lexer::is_id_start(*c))
+                                .peek_ahead()
+                                .is_some_and(|(_, _, c)| rustc_lexer::is_id_start(c))
                             {
                                 self.input_vec_index += 1;
                                 let prefix_end = r.end;
@@ -584,7 +592,7 @@ impl<'a> Parser<'a> {
     }
 
     fn input_vec_index2pos(&self, index: usize) -> usize {
-        if let Some(&(_, pos, _)) = self.input_vec.get(index) { pos } else { self.input.len() }
+        if let Some((_, pos, _)) = self.input_vec.get(index) { *pos } else { self.input.len() }
     }
 
     fn input_vec_index2range(&self, index: usize) -> Range<usize> {
@@ -618,11 +626,11 @@ impl<'a> Parser<'a> {
         }
 
         // fill character
-        if let Some(&(ref r, _, c)) = self.input_vec.get(self.input_vec_index) {
-            if let Some((_, _, '>' | '<' | '^')) = self.input_vec.get(self.input_vec_index + 1) {
+        if let Some((r, _, c)) = self.peek() {
+            if let Some((_, _, '>' | '<' | '^')) = self.peek_ahead() {
                 self.input_vec_index += 1;
                 spec.fill = Some(c);
-                spec.fill_span = Some(r.clone());
+                spec.fill_span = Some(r);
             }
         }
         // Alignment
@@ -701,7 +709,7 @@ impl<'a> Parser<'a> {
             }
         } else if let Some((range, _)) = self.consume_pos('?') {
             spec.ty = "?";
-            if let Some((r, _, c)) = self.input_vec.get(self.input_vec_index) {
+            if let Some((r, _, c)) = self.peek() {
                 match c {
                     '#' | 'x' | 'X' => self.errors.insert(
                         0,
@@ -788,8 +796,8 @@ impl<'a> Parser<'a> {
     /// Rust identifier, except that it can't start with `_` character.
     fn word(&mut self) -> &'a str {
         let index = self.input_vec_index;
-        match self.input_vec.get(self.input_vec_index) {
-            Some(&(ref r, i, c)) if rustc_lexer::is_id_start(c) => {
+        match self.peek() {
+            Some((ref r, i, c)) if rustc_lexer::is_id_start(c) => {
                 self.input_vec_index += 1;
                 (r.start, i)
             }
@@ -798,7 +806,7 @@ impl<'a> Parser<'a> {
             }
         };
         let (err_end, end): (usize, usize) = loop {
-            if let Some(&(ref r, i, c)) = self.input_vec.get(self.input_vec_index) {
+            if let Some((ref r, i, c)) = self.peek() {
                 if rustc_lexer::is_id_continue(c) {
                     self.input_vec_index += 1;
                 } else {
@@ -828,7 +836,7 @@ impl<'a> Parser<'a> {
         let mut found = false;
         let mut overflow = false;
         let start_index = self.input_vec_index;
-        while let Some(&(_, _, c)) = self.input_vec.get(self.input_vec_index) {
+        while let Some((_, _, c)) = self.peek() {
             if let Some(i) = c.to_digit(10) {
                 self.input_vec_index += 1;
                 let (tmp, mul_overflow) = cur.overflowing_mul(10);