refactor(common): Simplify StringInput implementation (#9071)

Author: kdy1

crates/swc_common/src/input.rs

@@ -9,7 +9,6 @@ pub type SourceFileInput<'a> = StringInput<'a>;
 /// Implementation of [Input].
 #[derive(Clone)]
 pub struct StringInput<'a> {
-    start_pos_of_iter: BytePos,
     last_pos: BytePos,
     /// Current cursor
     iter: str::CharIndices<'a>,
@@ -31,7 +30,6 @@ impl<'a> StringInput<'a> {
         assert!(start <= end);
 
         StringInput {
-            start_pos_of_iter: start,
             last_pos: start,
             orig: src,
             iter: src.char_indices(),
@@ -82,8 +80,8 @@ impl<'a> Input for StringInput<'a> {
 
     #[inline]
     unsafe fn bump(&mut self) {
-        if let Some((i, c)) = self.iter.next() {
-            self.last_pos = self.start_pos_of_iter + BytePos((i + c.len_utf8()) as u32);
+        if let Some((_, c)) = self.iter.next() {
+            self.last_pos = self.last_pos + BytePos((c.len_utf8()) as u32);
         } else {
             unsafe {
                 debug_unreachable!("bump should not be called when cur() == None");
@@ -131,7 +129,6 @@ impl<'a> Input for StringInput<'a> {
 
         self.iter = unsafe { s.get_unchecked(end_idx..) }.char_indices();
         self.last_pos = end;
-        self.start_pos_of_iter = end;
 
         ret
     }
@@ -155,7 +152,6 @@ impl<'a> Input for StringInput<'a> {
         let ret = unsafe { s.get_unchecked(..last) };
 
         self.last_pos = self.last_pos + BytePos(last as _);
-        self.start_pos_of_iter = self.last_pos;
         self.iter = unsafe { s.get_unchecked(last..) }.char_indices();
 
         ret
@@ -181,7 +177,6 @@ impl<'a> Input for StringInput<'a> {
         debug_assert!(last <= s.len());
 
         self.last_pos = self.last_pos + BytePos(last as _);
-        self.start_pos_of_iter = self.last_pos;
         self.iter = unsafe { s.get_unchecked(last..) }.char_indices();
 
         Some(self.last_pos)
@@ -195,7 +190,6 @@ impl<'a> Input for StringInput<'a> {
         debug_assert!(idx <= orig.len());
         let s = unsafe { orig.get_unchecked(idx..) };
         self.iter = s.char_indices();
-        self.start_pos_of_iter = to;
         self.last_pos = to;
     }
 
@@ -217,15 +211,8 @@ impl<'a> Input for StringInput<'a> {
     #[inline]
     fn eat_byte(&mut self, c: u8) -> bool {
         if self.is_byte(c) {
-            if let Some((i, _)) = self.iter.next() {
-                self.last_pos = self.start_pos_of_iter + BytePos((i + 1) as u32);
-            } else {
-                unsafe {
-                    debug_unreachable!(
-                        "We can't enter here as we already checked the state using `is_byte`"
-                    )
-                }
-            }
+            self.iter.next();
+            self.last_pos = self.last_pos + BytePos(1_u32);
             true
         } else {
             false
@@ -340,13 +327,11 @@ mod tests {
         with_test_sess("foo/d", |mut i| {
             assert_eq!(unsafe { i.slice(BytePos(1), BytePos(2)) }, "f");
             assert_eq!(i.last_pos, BytePos(2));
-            assert_eq!(i.start_pos_of_iter, BytePos(2));
             assert_eq!(i.cur(), Some('o'));
 
             assert_eq!(unsafe { i.slice(BytePos(2), BytePos(4)) }, "oo");
             assert_eq!(unsafe { i.slice(BytePos(1), BytePos(4)) }, "foo");
             assert_eq!(i.last_pos, BytePos(4));
-            assert_eq!(i.start_pos_of_iter, BytePos(4));
             assert_eq!(i.cur(), Some('/'));
         });
     }
@@ -356,13 +341,11 @@ mod tests {
         with_test_sess("load", |mut i| {
             assert_eq!(unsafe { i.slice(BytePos(1), BytePos(3)) }, "lo");
             assert_eq!(i.last_pos, BytePos(3));
-            assert_eq!(i.start_pos_of_iter, BytePos(3));
             assert_eq!(i.cur(), Some('a'));
             unsafe { i.reset_to(BytePos(1)) };
 
             assert_eq!(i.cur(), Some('l'));
             assert_eq!(i.last_pos, BytePos(1));
-            assert_eq!(i.start_pos_of_iter, BytePos(1));
         });
     }
 
@@ -371,12 +354,10 @@ mod tests {
         with_test_sess("foo/d", |mut i| {
             assert_eq!(i.cur_pos(), BytePos(1));
             assert_eq!(i.last_pos, BytePos(1));
-            assert_eq!(i.start_pos_of_iter, BytePos(1));
             assert_eq!(i.uncons_while(|c| c.is_alphabetic()), "foo");
 
             // assert_eq!(i.cur_pos(), BytePos(4));
             assert_eq!(i.last_pos, BytePos(4));
-            assert_eq!(i.start_pos_of_iter, BytePos(4));
             assert_eq!(i.cur(), Some('/'));
 
             unsafe {
@@ -398,10 +379,8 @@ mod tests {
         with_test_sess("foo/d", |mut i| {
             assert_eq!(i.cur_pos(), BytePos(1));
             assert_eq!(i.last_pos, BytePos(1));
-            assert_eq!(i.start_pos_of_iter, BytePos(1));
 
             assert_eq!(i.find(|c| c == '/'), Some(BytePos(5)));
-            assert_eq!(i.start_pos_of_iter, BytePos(5));
             assert_eq!(i.last_pos, BytePos(5));
             assert_eq!(i.cur(), Some('d'));
         });

crates/swc_ecma_parser/src/lexer/mod.rs

@@ -25,6 +25,7 @@ use crate::{
 };
 
 mod comments_buffer;
+#[deprecated = "Directly use swc_common::input instead"]
 pub mod input;
 mod jsx;
 mod number;