feat(es/typescript): Improve fast TS strip (#9167)

bindings/binding_typescript_wasm/__tests__/__snapshots__/transform.js.snap

@@ -2,9 +2,18 @@
 
 exports[`transform in strip-only mode should remove declare enum 1`] = `"                   "`;
 
-exports[`transform in strip-only mode should remove declare enum 2`] = `"                                                          "`;
+exports[`transform in strip-only mode should remove declare enum 2`] = `
+"                  
+                     
+                 "
+`;
 
-exports[`transform in strip-only mode should remove declare enum 3`] = `"                                                                                          "`;
+exports[`transform in strip-only mode should remove declare enum 3`] = `
+"                  
+                          
+                      
+                     "
+`;
 
 exports[`transform in strip-only mode should strip complex expressions 1`] = `
 "const foo = {

crates/swc_fast_ts_strip/src/lib.rs

@@ -168,22 +168,28 @@ impl TsStrip {
         &self.src[(span.lo.0 - 1) as usize..(span.hi.0 - 1) as usize]
     }
 
-    fn get_next_token(&self, pos: BytePos) -> &TokenAndSpan {
+    fn get_next_token_index(&self, pos: BytePos) -> usize {
         let index = self.tokens.binary_search_by_key(&pos, |t| t.span.lo);
-        let index = match index {
+        match index {
             Ok(index) => index,
             Err(index) => index,
-        };
-        &self.tokens[index]
+        }
     }
 
-    fn get_prev_token(&self, pos: BytePos) -> &TokenAndSpan {
+    fn get_next_token(&self, pos: BytePos) -> &TokenAndSpan {
+        &self.tokens[self.get_next_token_index(pos)]
+    }
+
+    fn get_prev_token_index(&self, pos: BytePos) -> usize {
         let index = self.tokens.binary_search_by_key(&pos, |t| t.span.lo);
-        let index = match index {
+        match index {
             Ok(index) => index,
             Err(index) => index - 1,
-        };
-        &self.tokens[index]
+        }
+    }
+
+    fn get_prev_token(&self, pos: BytePos) -> &TokenAndSpan {
+        &self.tokens[self.get_prev_token_index(pos)]
     }
 }
 
@@ -218,7 +224,7 @@ impl Visit for TsStrip {
                 //     1;
                 // ```
 
-                self.add_overwrite(ret.span_hi(), b')');
+                self.add_overwrite(ret.span_hi() - BytePos(1), b')');
             }
         }
 
@@ -264,6 +270,10 @@ impl Visit for TsStrip {
         if !n.implements.is_empty() {
             let implements =
                 self.get_prev_token(n.implements.first().unwrap().span_lo() - BytePos(1));
+            debug_assert_eq!(
+                implements.token,
+                Token::Word(Word::Ident(IdentLike::Known(KnownIdent::Implements)))
+            );
 
             let last = n.implements.last().unwrap();
             let span = span(implements.span.lo, last.span.hi);
@@ -279,13 +289,14 @@ impl Visit for TsStrip {
             return;
         }
 
-        let key_span = n.key.span_hi();
-        let method_pos = n.function.span_lo();
+        let key_pos = n.key.span_lo();
+        let mut pos = n.span_lo();
+        let mut index = self.get_next_token_index(pos);
 
-        let mut pos = method_pos;
-        while pos < key_span {
-            let TokenAndSpan { token, span, .. } = self.get_next_token(pos);
+        while pos < key_pos {
+            let TokenAndSpan { token, span, .. } = &self.tokens[index];
             pos = span.hi;
+            index += 1;
             match token {
                 Token::Word(Word::Ident(IdentLike::Known(
                     KnownIdent::Public | KnownIdent::Protected | KnownIdent::Private,
@@ -308,13 +319,14 @@ impl Visit for TsStrip {
             return;
         }
 
-        let key_span = n.key.span_hi();
-        let method_pos = n.span_lo();
+        let key_pos = n.key.span_lo();
+        let mut pos = n.span_lo();
+        let mut index = self.get_next_token_index(pos);
 
-        let mut pos = method_pos;
-        while pos < key_span {
-            let TokenAndSpan { token, span, .. } = self.get_next_token(pos);
+        while pos < key_pos {
+            let TokenAndSpan { token, span, .. } = &self.tokens[index];
             pos = span.hi;
+            index += 1;
             match token {
                 Token::Word(Word::Ident(IdentLike::Known(
                     KnownIdent::Readonly

crates/swc_fast_ts_strip/tests/fixture/test-case-1.js

@@ -142,36 +142,41 @@ void 0;
 // `=>` spanning line cases:
 {
     ( 
-             )=>
+            ) =>
         1
 };
 {
     (  
-           )=>
+          ) =>
         1
 };
 {
     (
 
-             )=>
+            ) =>
         1
 };
 {
     (
 
 
-         )=>
+        ) =>
         1
 };
 {
     (
 
 
-         )=>
+        ) =>
         1
 };
 {
     (a, b, c    = []       /*comment-1*/ /*comment-2*/ 
-           )=>
+          ) =>
         1
-};
+};
+
+
+    (  
+          )=>
+        1;

crates/swc_fast_ts_strip/tests/fixture/test-case-1.ts

@@ -174,4 +174,9 @@ void 0;
     (a, b, c: D = [] as any/*comment-1*/)/*comment-2*/:
         any =>
         1
-};
+};
+
+
+    ():
+        any=>
+        1;