3 files changed, 136 insertions, 2 deletions

diff --git a/crates/ra_hir_expand/src/quote.rs b/crates/ra_hir_expand/src/quote.rs
index 3fd4233da..219bc2097 100644
--- a/crates/ra_hir_expand/src/quote.rs
+++ b/crates/ra_hir_expand/src/quote.rs
@@ -232,7 +232,7 @@ mod tests {
         let quoted = quote!(#a);
         assert_eq!(quoted.to_string(), "hello");
         let t = format!("{:?}", quoted);
-        assert_eq!(t, "Subtree { delimiter: None, token_trees: [Leaf(Ident(Ident { text: \"hello\", id: TokenId(4294967295) }))] }");
+        assert_eq!(t, "SUBTREE $\n  IDENT   hello 4294967295");
     }
 
     #[test]
diff --git a/crates/ra_mbe/src/tests.rs b/crates/ra_mbe/src/tests.rs
index 254318e23..1ef6f6eed 100644
--- a/crates/ra_mbe/src/tests.rs
+++ b/crates/ra_mbe/src/tests.rs
@@ -142,6 +142,79 @@ macro_rules! impl_froms {
 }
 
 #[test]
+fn test_convert_tt2() {
+    parse_macro(
+        r#"
+macro_rules! impl_froms {
+    ($e:ident: $($v:ident),*) => {
+        $(
+            impl From<$v> for $e {
+                fn from(it: $v) -> $e {
+                    $e::$v(it)
+                }
+            }
+        )*
+    }
+}
+"#,
+    )
+    .assert_expand(
+        "impl_froms!(TokenTree: Leaf, Subtree);",
+        r#"
+SUBTREE $
+  IDENT   impl 20
+  IDENT   From 21
+  PUNCH   < [joint] 22
+  IDENT   Leaf 53
+  PUNCH   > [alone] 25
+  IDENT   for 26
+  IDENT   TokenTree 51
+  SUBTREE {} 29
+    IDENT   fn 30
+    IDENT   from 31
+    SUBTREE () 32
+      IDENT   it 33
+      PUNCH   : [alone] 34
+      IDENT   Leaf 53
+    PUNCH   - [joint] 37
+    PUNCH   > [alone] 38
+    IDENT   TokenTree 51
+    SUBTREE {} 41
+      IDENT   TokenTree 51
+      PUNCH   : [joint] 44
+      PUNCH   : [joint] 45
+      IDENT   Leaf 53
+      SUBTREE () 48
+        IDENT   it 49
+  IDENT   impl 20
+  IDENT   From 21
+  PUNCH   < [joint] 22
+  IDENT   Subtree 55
+  PUNCH   > [alone] 25
+  IDENT   for 26
+  IDENT   TokenTree 51
+  SUBTREE {} 29
+    IDENT   fn 30
+    IDENT   from 31
+    SUBTREE () 32
+      IDENT   it 33
+      PUNCH   : [alone] 34
+      IDENT   Subtree 55
+    PUNCH   - [joint] 37
+    PUNCH   > [alone] 38
+    IDENT   TokenTree 51
+    SUBTREE {} 41
+      IDENT   TokenTree 51
+      PUNCH   : [joint] 44
+      PUNCH   : [joint] 45
+      IDENT   Subtree 55
+      SUBTREE () 48
+        IDENT   it 49
+"#,
+    );
+}
+
+#[test]
 fn test_expr_order() {
     let expanded = parse_macro(
         r#"
@@ -1479,6 +1552,12 @@ impl MacroFixture {
         assert_eq!(expansion.to_string(), expected);
     }
 
+    fn assert_expand(&self, invocation: &str, expected: &str) {
+        let expansion = self.expand_tt(invocation);
+        let actual = format!("{:?}", expansion);
+        test_utils::assert_eq_text!(&actual.trim(), &expected.trim());
+    }
+
     fn assert_expand_items(&self, invocation: &str, expected: &str) -> &MacroFixture {
         self.assert_expansion(FragmentKind::Items, invocation, expected);
         self
diff --git a/crates/ra_tt/src/lib.rs b/crates/ra_tt/src/lib.rs
index bd484aa30..5248e026c 100644
--- a/crates/ra_tt/src/lib.rs
+++ b/crates/ra_tt/src/lib.rs
@@ -57,7 +57,7 @@ pub enum Leaf {
 }
 impl_froms!(Leaf: Literal, Punct, Ident);
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash, Default)]
+#[derive(Clone, PartialEq, Eq, Hash, Default)]
 pub struct Subtree {
     pub delimiter: Option<Delimiter>,
     pub token_trees: Vec<TokenTree>,
@@ -101,6 +101,61 @@ pub struct Ident {
     pub id: TokenId,
 }
 
+fn print_debug_subtree(f: &mut fmt::Formatter<'_>, subtree: &Subtree, level: usize) -> fmt::Result {
+    let align = std::iter::repeat("  ").take(level).collect::<String>();
+
+    let aux = match subtree.delimiter.map(|it| (it.kind, it.id.0)) {
+        None => "$".to_string(),
+        Some((DelimiterKind::Parenthesis, id)) => format!("() {}", id),
+        Some((DelimiterKind::Brace, id)) => format!("{{}} {}", id),
+        Some((DelimiterKind::Bracket, id)) => format!("[] {}", id),
+    };
+
+    if subtree.token_trees.is_empty() {
+        write!(f, "{}SUBTREE {}", align, aux)?;
+    } else {
+        writeln!(f, "{}SUBTREE {}", align, aux)?;
+        for (idx, child) in subtree.token_trees.iter().enumerate() {
+            print_debug_token(f, child, level + 1)?;
+            if idx != subtree.token_trees.len() - 1 {
+                writeln!(f, "")?;
+            }
+        }
+    }
+
+    Ok(())
+}
+
+fn print_debug_token(f: &mut fmt::Formatter<'_>, tkn: &TokenTree, level: usize) -> fmt::Result {
+    let align = std::iter::repeat("  ").take(level).collect::<String>();
+
+    match tkn {
+        TokenTree::Leaf(leaf) => match leaf {
+            Leaf::Literal(lit) => write!(f, "{}LITERAL {} {}", align, lit.text, lit.id.0)?,
+            Leaf::Punct(punct) => write!(
+                f,
+                "{}PUNCH   {} [{}] {}",
+                align,
+                punct.char,
+                if punct.spacing == Spacing::Alone { "alone" } else { "joint" },
+                punct.id.0
+            )?,
+            Leaf::Ident(ident) => write!(f, "{}IDENT   {} {}", align, ident.text, ident.id.0)?,
+        },
+        TokenTree::Subtree(subtree) => {
+            print_debug_subtree(f, subtree, level)?;
+        }
+    }
+
+    Ok(())
+}
+
+impl Debug for Subtree {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        print_debug_subtree(f, self, 0)
+    }
+}
+
 impl fmt::Display for TokenTree {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {