Fix tt::Punct's spacing calculation

crates/mbe/src/syntax_bridge/tests.rs

@@ -0,0 +1,93 @@
+use std::collections::HashMap;
+
+use syntax::{ast, AstNode};
+use test_utils::extract_annotations;
+use tt::{
+    buffer::{TokenBuffer, TokenTreeRef},
+    Leaf, Punct, Spacing,
+};
+
+use super::syntax_node_to_token_tree;
+
+fn check_punct_spacing(fixture: &str) {
+    let source_file = ast::SourceFile::parse(fixture).ok().unwrap();
+    let (subtree, token_map) = syntax_node_to_token_tree(source_file.syntax());
+    let mut annotations: HashMap<_, _> = extract_annotations(fixture)
+        .into_iter()
+        .map(|(range, annotation)| {
+            let token = token_map.token_by_range(range).expect("no token found");
+            let spacing = match annotation.as_str() {
+                "Alone" => Spacing::Alone,
+                "Joint" => Spacing::Joint,
+                a => panic!("unknown annotation: {}", a),
+            };
+            (token, spacing)
+        })
+        .collect();
+
+    let buf = TokenBuffer::from_subtree(&subtree);
+    let mut cursor = buf.begin();
+    while !cursor.eof() {
+        while let Some(token_tree) = cursor.token_tree() {
+            if let TokenTreeRef::Leaf(Leaf::Punct(Punct { spacing, id, .. }), _) = token_tree {
+                if let Some(expected) = annotations.remove(&id) {
+                    assert_eq!(expected, *spacing);
+                }
+            }
+            cursor = cursor.bump_subtree();
+        }
+        cursor = cursor.bump();
+    }
+
+    assert!(annotations.is_empty(), "unchecked annotations: {:?}", annotations);
+}
+
+#[test]
+fn punct_spacing() {
+    check_punct_spacing(
+        r#"
+fn main() {
+    0+0;
+   //^ Alone
+    0+(0);
+   //^ Alone
+    0<=0;
+   //^ Joint
+   // ^ Alone
+    0<=(0);
+   // ^ Alone
+    a=0;
+   //^ Alone
+    a=(0);
+   //^ Alone
+    a+=0;
+   //^ Joint
+   // ^ Alone
+    a+=(0);
+   // ^ Alone
+    a&&b;
+   //^ Joint
+   // ^ Alone
+    a&&(b);
+   // ^ Alone
+    foo::bar;
+   //  ^ Joint
+   //   ^ Alone
+    use foo::{bar,baz,};
+   //       ^ Alone
+   //            ^ Alone
+   //                ^ Alone
+    struct Struct<'a> {};
+   //            ^ Joint
+   //             ^ Joint
+    Struct::<0>;
+   //       ^ Alone
+    Struct::<{0}>;
+   //       ^ Alone
+    ;;
+  //^ Joint
+  // ^ Alone
+}
+        "#,
+    );
+}