Don't allocate when traversing children

src/yellow/syntax.rs

@@ -11,8 +11,8 @@ impl TreeRoot for Arc<SyntaxRoot> {}
 impl<'a> TreeRoot for &'a SyntaxRoot {}
 
 #[derive(Clone, Copy)]
-pub struct SyntaxNode<ROOT: TreeRoot = Arc<SyntaxRoot>> {
-    pub(crate) root: ROOT,
+pub struct SyntaxNode<R: TreeRoot = Arc<SyntaxRoot>> {
+    pub(crate) root: R,
     // Guaranteed to not dangle, because `root` holds a
     // strong reference to red's ancestor
     red: ptr::NonNull<RedNode>,
@@ -52,7 +52,7 @@ pub(crate) fn new_owned(root: SyntaxRoot) -> Self {
     }
 }
 
-impl<ROOT: TreeRoot> SyntaxNode<ROOT> {
+impl<R: TreeRoot> SyntaxNode<R> {
     pub fn borrow<'a>(&'a self) -> SyntaxNode<&'a SyntaxRoot> {
         SyntaxNode {
             root: &*self.root,
@@ -73,20 +73,18 @@ pub fn text(&self) -> String {
         self.red().green().text()
     }
 
-    pub fn children(&self) -> Vec<SyntaxNode<ROOT>> {
+    pub fn children<'a>(&'a self) -> impl Iterator<Item=SyntaxNode<R>> + 'a {
         let red = self.red();
         let n_children = red.n_children();
-        let mut res = Vec::with_capacity(n_children);
-        for i in 0..n_children {
-            res.push(SyntaxNode {
+        (0..n_children).map(move |i| {
+            SyntaxNode {
                 root: self.root.clone(),
                 red: red.nth_child(i),
-            });
             }
-        res
+        })
     }
 
-    pub fn parent(&self) -> Option<SyntaxNode<ROOT>> {
+    pub fn parent(&self) -> Option<SyntaxNode<R>> {
         let parent = self.red().parent()?;
         Some(SyntaxNode {
             root: self.root.clone(),
@@ -99,7 +97,7 @@ fn red(&self) -> &RedNode {
     }
 }
 
-impl<ROOT: TreeRoot> fmt::Debug for SyntaxNode<ROOT> {
+impl<R: TreeRoot> fmt::Debug for SyntaxNode<R> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         write!(fmt, "{:?}@{:?}", self.kind(), self.range())?;
         if has_short_text(self.kind()) {

tests/data/parser/inline/0041_type_param_bounds.rs

@@ -0,0 +1 @@
+struct S<T: 'a + ?Sized + (Copy)>;

tests/data/parser/inline/0041_type_param_bounds.txt

@@ -0,0 +1,33 @@
+FILE@[0; 35)
+  STRUCT_ITEM@[0; 35)
+    STRUCT_KW@[0; 6)
+    NAME@[6; 8)
+      WHITESPACE@[6; 7)
+      IDENT@[7; 8) "S"
+    TYPE_PARAM_LIST@[8; 33)
+      L_ANGLE@[8; 9)
+      TYPE_PARAM@[9; 32)
+        IDENT@[9; 10) "T"
+        COLON@[10; 11)
+        WHITESPACE@[11; 12)
+        LIFETIME@[12; 14) "'a"
+        WHITESPACE@[14; 15)
+        PLUS@[15; 16)
+        WHITESPACE@[16; 17)
+        QUESTION@[17; 18)
+        PATH@[18; 24)
+          PATH_SEGMENT@[18; 24)
+            NAME_REF@[18; 24)
+              IDENT@[18; 23) "Sized"
+              WHITESPACE@[23; 24)
+        PLUS@[24; 25)
+        WHITESPACE@[25; 26)
+        L_PAREN@[26; 27)
+        PATH@[27; 31)
+          PATH_SEGMENT@[27; 31)
+            NAME_REF@[27; 31)
+              IDENT@[27; 31) "Copy"
+        R_PAREN@[31; 32)
+      R_ANGLE@[32; 33)
+    SEMI@[33; 34)
+    WHITESPACE@[34; 35)

tests/data/parser/inline/0042_type_param_default.rs

@@ -0,0 +1 @@
+struct S<T = i32>;

tests/data/parser/inline/0042_type_param_default.txt

@@ -0,0 +1,21 @@
+FILE@[0; 19)
+  STRUCT_ITEM@[0; 19)
+    STRUCT_KW@[0; 6)
+    NAME@[6; 8)
+      WHITESPACE@[6; 7)
+      IDENT@[7; 8) "S"
+    TYPE_PARAM_LIST@[8; 17)
+      L_ANGLE@[8; 9)
+      TYPE_PARAM@[9; 16)
+        IDENT@[9; 10) "T"
+        WHITESPACE@[10; 11)
+        EQ@[11; 12)
+        PATH_TYPE@[12; 16)
+          PATH@[12; 16)
+            PATH_SEGMENT@[12; 16)
+              NAME_REF@[12; 16)
+                WHITESPACE@[12; 13)
+                IDENT@[13; 16) "i32"
+      R_ANGLE@[16; 17)
+    SEMI@[17; 18)
+    WHITESPACE@[18; 19)