Merge #3482

3482: Fix regression from #3451 r=matklad a=edwin0cheng

There is a regression from #3451 such that the following code has failed to parse in raw item collecting phase:

```rust
macro_rules! with_std { 
 	($($i:item)*) => ($(#[cfg(feature = "std")]$i)*) 
}

with_std! {
	mod macros;
	mod others;
}
```

### Rationale

We always assume the last token of an statement will not end with a whitespace, which is true. It is because in parsing phase,  we always emit `SyntaxNode` before any whitespace. Such that in various parts of RA code, we solely check the semi-colon by using `SyntaxNode::last_child_token() == ";"` . 

However, in #3451, we insert some whitespaces between puncts such that we broke above assumption. This PR fixed this bug by make sure we don't add any whitespace if it is a semicolon.


Co-authored-by: Edwin Cheng <[email protected]>

Author: bors[bot]

crates/ra_mbe/src/syntax_bridge.rs

@@ -448,7 +448,9 @@ impl<'a> TreeSink for TtTreeSink<'a> {
             Some(tt::TokenTree::Leaf(tt::Leaf::Punct(_))),
         ) = (last.token_tree(), next.token_tree())
         {
-            if curr.spacing == tt::Spacing::Alone {
+            // Note: We always assume the semi-colon would be the last token in
+            // other parts of RA such that we don't add whitespace here.
+            if curr.spacing == tt::Spacing::Alone && curr.char != ';' {
                 self.inner.token(WHITESPACE, " ".into());
                 self.text_pos += TextUnit::of_char(' ');
             }

crates/ra_mbe/src/tests.rs

@@ -1593,6 +1593,60 @@ fn test_repeat_bad_var() {
     .assert_expand_items("foo!(b0 b1);", "b0 b1");
 }
 
+#[test]
+fn test_no_space_after_semi_colon() {
+    let expanded = parse_macro(
+        r#"
+        macro_rules! with_std { ($($i:item)*) => ($(#[cfg(feature = "std")]$i)*) }
+    "#,
+    )
+    .expand_items(r#"with_std! {mod m;mod f;}"#);
+
+    let dump = format!("{:#?}", expanded);
+    assert_eq_text!(
+        dump.trim(),
+        r###"MACRO_ITEMS@[0; 52)
+  MODULE@[0; 26)
+    ATTR@[0; 21)
+      POUND@[0; 1) "#"
+      L_BRACK@[1; 2) "["
+      PATH@[2; 5)
+        PATH_SEGMENT@[2; 5)
+          NAME_REF@[2; 5)
+            IDENT@[2; 5) "cfg"
+      TOKEN_TREE@[5; 20)
+        L_PAREN@[5; 6) "("
+        IDENT@[6; 13) "feature"
+        EQ@[13; 14) "="
+        STRING@[14; 19) "\"std\""
+        R_PAREN@[19; 20) ")"
+      R_BRACK@[20; 21) "]"
+    MOD_KW@[21; 24) "mod"
+    NAME@[24; 25)
+      IDENT@[24; 25) "m"
+    SEMI@[25; 26) ";"
+  MODULE@[26; 52)
+    ATTR@[26; 47)
+      POUND@[26; 27) "#"
+      L_BRACK@[27; 28) "["
+      PATH@[28; 31)
+        PATH_SEGMENT@[28; 31)
+          NAME_REF@[28; 31)
+            IDENT@[28; 31) "cfg"
+      TOKEN_TREE@[31; 46)
+        L_PAREN@[31; 32) "("
+        IDENT@[32; 39) "feature"
+        EQ@[39; 40) "="
+        STRING@[40; 45) "\"std\""
+        R_PAREN@[45; 46) ")"
+      R_BRACK@[46; 47) "]"
+    MOD_KW@[47; 50) "mod"
+    NAME@[50; 51)
+      IDENT@[50; 51) "f"
+    SEMI@[51; 52) ";""###,
+    );
+}
+
 #[test]
 fn test_expand_bad_literal() {
     parse_macro(