fix(codegen): don't emit space between postfix -- and > when minifying (#23036)

## What

`a-- > b` was minified as `a-- >b` (a space before `>`) to avoid producing the `-->` token sequence. But `-->` is only an HTML close comment (`SingleLineHTMLCloseComment`) at the **start of a line**, and a postfix `--` always has an operand before it — so `a-->b` is never a comment and always parses as `(a--) > b`.

| Input | Before | After |
| --- | --- | --- |
| `while (i-- > 0) f()` | `while(i-- >0)f()` | `while(i-->0)f()` |
| `x = a-- > b` | `x=a-- >b` | `x=a-->b` |

Verified in node (`while(i-->0)` yields `[2,1,0]`). This goes one step beyond esbuild, which keeps the conservative space.

The `< ! --` guard (avoiding `<!--`, which *can* appear mid-line) is left untouched.

crates/oxc_codegen/src/lib.rs

@@ -826,22 +826,21 @@ impl<'a> Codegen<'a> {
         // "x + + y" => "x+ +y"
         // "x ++ + y" => "x+++y"
         // "x + ++ y" => "x+ ++y"
-        // "-- >" => "-- >"
         // "< ! --" => "<! --"
+        // Note: `a-- > b` does not need a space (`a-->b` is `(a--) > b`); `-->` is
+        // only an HTML close comment at the start of a line, and a postfix `--`
+        // always has an operand before it.
         let bin_op_add = Operator::Binary(BinaryOperator::Addition);
         let bin_op_sub = Operator::Binary(BinaryOperator::Subtraction);
         let un_op_pos = Operator::Unary(UnaryOperator::UnaryPlus);
         let un_op_pre_inc = Operator::Update(UpdateOperator::Increment);
         let un_op_neg = Operator::Unary(UnaryOperator::UnaryNegation);
         let un_op_pre_dec = Operator::Update(UpdateOperator::Decrement);
-        let un_op_post_dec = Operator::Update(UpdateOperator::Decrement);
-        let bin_op_gt = Operator::Binary(BinaryOperator::GreaterThan);
         let un_op_not = Operator::Unary(UnaryOperator::LogicalNot);
         if ((prev == bin_op_add || prev == un_op_pos)
             && (next == bin_op_add || next == un_op_pos || next == un_op_pre_inc))
             || ((prev == bin_op_sub || prev == un_op_neg)
                 && (next == bin_op_sub || next == un_op_neg || next == un_op_pre_dec))
-            || (prev == un_op_post_dec && next == bin_op_gt)
             || (prev == un_op_not
                 && next == un_op_pre_dec
                 // `prev == UnaryOperator::LogicalNot` which means last byte is ASCII,

crates/oxc_codegen/tests/integration/esbuild.rs

@@ -799,7 +799,9 @@ fn test_whitespace() {
     test_minify("x + y--", "x+y--;");
     test_minify("x - y--", "x-y--;");
 
-    test_minify("x-- > y", "x-- >y;");
+    // `-->` is only an HTML close comment at the start of a line, and `x--` always
+    // has an operand before it, so no space is needed.
+    test_minify("x-- > y", "x-->y;");
     test_minify("x < !--y", "x<! --y;");
     test_minify("x > !--y", "x>!--y;");
     test_minify("!--y", "!--y;");

tasks/minsize/minsize.snap

@@ -23,5 +23,5 @@ Original   | minified   | minified   | gzip       | gzip       | Iterations | Fi
 
 6.69 MB    | 2.22 MB    | 2.31 MB    | 458.45 kB  | 488.28 kB  |          4 | antd.js    
 
-10.95 MB   | 3.33 MB    | 3.49 MB    | 853.33 kB  | 915.50 kB  |          4 | typescript.js 
+10.95 MB   | 3.33 MB    | 3.49 MB    | 853.35 kB  | 915.50 kB  |          4 | typescript.js