3 files changed, 359 insertions, 123 deletions

diff --git a/crates/libsyntax2/src/lib.rs b/crates/libsyntax2/src/lib.rs
index e761fa358..eb271762e 100644
--- a/crates/libsyntax2/src/lib.rs
+++ b/crates/libsyntax2/src/lib.rs
@@ -27,6 +27,10 @@ extern crate parking_lot;
 extern crate smol_str;
 extern crate text_unit;
 
+#[cfg(test)]
+#[macro_use]
+extern crate test_utils;
+
 pub mod algo;
 pub mod ast;
 mod lexer;
@@ -35,6 +39,7 @@ mod token_set;
 mod parser_api;
 mod grammar;
 mod parser_impl;
+mod reparsing;
 
 mod syntax_kinds;
 mod yellow;
@@ -49,12 +54,11 @@ pub use {
     lexer::{tokenize, Token},
     syntax_kinds::SyntaxKind,
     yellow::{SyntaxNode, SyntaxNodeRef, OwnedRoot, RefRoot, TreeRoot, SyntaxError},
+    reparsing::AtomEdit,
 };
 
 use {
-    SyntaxKind::*,
     yellow::{GreenNode, SyntaxRoot},
-    parser_api::Parser,
 };
 
 #[derive(Clone, Debug, Hash)]
@@ -82,25 +86,11 @@ impl File {
         self.incremental_reparse(edit).unwrap_or_else(|| self.full_reparse(edit))
     }
     pub fn incremental_reparse(&self, edit: &AtomEdit) -> Option<File> {
-        let (node, reparser) = find_reparsable_node(self.syntax(), edit.delete)?;
-        let text = replace_range(
-            node.text().to_string(),
-            edit.delete - node.range().start(),
-            &edit.insert,
-        );
-        let tokens = tokenize(&text);
-        if !is_balanced(&tokens) {
-            return None;
-        }
-        let (green, new_errors) = parser_impl::parse_with::<yellow::GreenBuilder>(
-            &text, &tokens, reparser,
-        );
-        let green_root = node.replace_with(green);
-        let errors = merge_errors(self.errors(), new_errors, node, edit);
-        Some(File::new(green_root, errors))
+        reparsing::incremental_reparse(self.syntax(), edit, self.errors())
+            .map(|(green_node, errors)| File::new(green_node, errors))
     }
     fn full_reparse(&self, edit: &AtomEdit) -> File {
-        let text = replace_range(self.syntax().text().to_string(), edit.delete, &edit.insert);
+        let text = text_utils::replace_range(self.syntax().text().to_string(), edit.delete, &edit.insert);
         File::parse(&text)
     }
     pub fn ast(&self) -> ast::Root {
@@ -113,107 +103,3 @@ impl File {
         self.syntax().root.syntax_root().errors.clone()
     }
 }
-
-#[derive(Debug, Clone)]
-pub struct AtomEdit {
-    pub delete: TextRange,
-    pub insert: String,
-}
-
-impl AtomEdit {
-    pub fn replace(range: TextRange, replace_with: String) -> AtomEdit {
-        AtomEdit { delete: range, insert: replace_with }
-    }
-
-    pub fn delete(range: TextRange) -> AtomEdit {
-        AtomEdit::replace(range, String::new())
-    }
-
-    pub fn insert(offset: TextUnit, text: String) -> AtomEdit {
-        AtomEdit::replace(TextRange::offset_len(offset, 0.into()), text)
-    }
-}
-
-fn find_reparsable_node(node: SyntaxNodeRef, range: TextRange) -> Option<(SyntaxNodeRef, fn(&mut Parser))> {
-    let node = algo::find_covering_node(node, range);
-    return algo::ancestors(node)
-        .filter_map(|node| reparser(node).map(|r| (node, r)))
-        .next();
-
-    fn reparser(node: SyntaxNodeRef) -> Option<fn(&mut Parser)> {
-        let res = match node.kind() {
-            BLOCK => grammar::block,
-            NAMED_FIELD_DEF_LIST => grammar::named_field_def_list,
-            NAMED_FIELD_LIST => grammar::named_field_list,
-            ENUM_VARIANT_LIST => grammar::enum_variant_list,
-            MATCH_ARM_LIST => grammar::match_arm_list,
-            USE_TREE_LIST => grammar::use_tree_list,
-            EXTERN_ITEM_LIST => grammar::extern_item_list,
-            TOKEN_TREE if node.first_child().unwrap().kind() == L_CURLY => grammar::token_tree,
-            ITEM_LIST => {
-                let parent = node.parent().unwrap();
-                match parent.kind() {
-                    IMPL_ITEM => grammar::impl_item_list,
-                    TRAIT_DEF => grammar::trait_item_list,
-                    MODULE => grammar::mod_item_list,
-                    _ => return None,
-                }
-            },
-            _ => return None,
-        };
-        Some(res)
-    }
-}
-
-pub /*(meh)*/ fn replace_range(mut text: String, range: TextRange, replace_with: &str) -> String {
-    let start = u32::from(range.start()) as usize;
-    let end = u32::from(range.end()) as usize;
-    text.replace_range(start..end, replace_with);
-    text
-}
-
-fn is_balanced(tokens: &[Token]) -> bool {
-    if tokens.len() == 0
-       || tokens.first().unwrap().kind != L_CURLY
-       || tokens.last().unwrap().kind != R_CURLY {
-        return false
-    }
-    let mut balance = 0usize;
-    for t in tokens.iter() {
-        match t.kind {
-            L_CURLY => balance += 1,
-            R_CURLY => balance = match balance.checked_sub(1) {
-                Some(b) => b,
-                None => return false,
-            },
-            _ => (),
-        }
-    }
-    balance == 0
-}
-
-fn merge_errors(
-    old_errors: Vec<SyntaxError>,
-    new_errors: Vec<SyntaxError>,
-    old_node: SyntaxNodeRef,
-    edit: &AtomEdit,
-) -> Vec<SyntaxError> {
-    let mut res = Vec::new();
-    for e in old_errors {
-        if e.offset < old_node.range().start() {
-            res.push(e)
-        } else if e.offset > old_node.range().end() {
-            res.push(SyntaxError {
-                msg: e.msg,
-                offset: e.offset + TextUnit::of_str(&edit.insert) - edit.delete.len(),
-            })
-        }
-    }
-    for e in new_errors {
-        res.push(SyntaxError {
-            msg: e.msg,
-            offset: e.offset + old_node.range().start(),
-        })
-    }
-    res
-}
diff --git a/crates/libsyntax2/src/reparsing.rs b/crates/libsyntax2/src/reparsing.rs
new file mode 100644
index 000000000..da44913c5
--- /dev/null
+++ b/crates/libsyntax2/src/reparsing.rs
@@ -0,0 +1,343 @@
+use algo;
+use grammar;
+use lexer::{tokenize, Token};
+use text_unit::{TextRange, TextUnit};
+use yellow::{self, SyntaxNodeRef, GreenNode, SyntaxError};
+use parser_impl;
+use parser_api::Parser;
+use {
+    SyntaxKind::*,
+};
+use text_utils::replace_range;
+
+#[derive(Debug, Clone)]
+pub struct AtomEdit {
+    pub delete: TextRange,
+    pub insert: String,
+}
+
+impl AtomEdit {
+    pub fn replace(range: TextRange, replace_with: String) -> AtomEdit {
+        AtomEdit { delete: range, insert: replace_with }
+    }
+
+    pub fn delete(range: TextRange) -> AtomEdit {
+        AtomEdit::replace(range, String::new())
+    }
+
+    pub fn insert(offset: TextUnit, text: String) -> AtomEdit {
+        AtomEdit::replace(TextRange::offset_len(offset, 0.into()), text)
+    }
+}
+
+pub(crate) fn incremental_reparse(
+    node: SyntaxNodeRef,
+    edit: &AtomEdit,
+    errors: Vec<SyntaxError>,
+) -> Option<(GreenNode, Vec<SyntaxError>)> {
+    let (node, green, new_errors) =
+        reparse_leaf(node, &edit).or_else(|| reparse_block(node, &edit))?;
+    let green_root = node.replace_with(green);
+    let errors = merge_errors(errors, new_errors, node, edit);
+    Some((green_root, errors))
+}
+
+fn reparse_leaf<'node>(
+    node: SyntaxNodeRef<'node>,
+    edit: &AtomEdit,
+) -> Option<(SyntaxNodeRef<'node>, GreenNode, Vec<SyntaxError>)> {
+    let node = algo::find_covering_node(node, edit.delete);
+    match node.kind() {
+        | WHITESPACE
+        | COMMENT
+        | DOC_COMMENT
+        | IDENT
+        | STRING
+        | RAW_STRING => {
+            let text = get_text_after_edit(node, &edit);
+            let tokens = tokenize(&text);
+            let token = match tokens[..] {
+                [token] if token.kind == node.kind() => token,
+                _ => return None,
+            };
+
+            if token.kind == IDENT && is_contextual_kw(&text) {
+                return None;
+            }
+
+            let green = GreenNode::new_leaf(node.kind(), &text);
+            let new_errors = vec![];
+            Some((node, green, new_errors))
+        }
+        _ => None,
+    }
+}
+
+fn reparse_block<'node>(
+    node: SyntaxNodeRef<'node>,
+    edit: &AtomEdit,
+) -> Option<(SyntaxNodeRef<'node>, GreenNode, Vec<SyntaxError>)> {
+    let (node, reparser) = find_reparsable_node(node, edit.delete)?;
+    let text = get_text_after_edit(node, &edit);
+    let tokens = tokenize(&text);
+    if !is_balanced(&tokens) {
+        return None;
+    }
+    let (green, new_errors) =
+        parser_impl::parse_with::<yellow::GreenBuilder>(
+            &text, &tokens, reparser,
+        );
+    Some((node, green, new_errors))
+}
+
+fn get_text_after_edit(node: SyntaxNodeRef, edit: &AtomEdit) -> String {
+    replace_range(
+        node.text().to_string(),
+        edit.delete - node.range().start(),
+        &edit.insert,
+    )
+}
+
+fn is_contextual_kw(text: &str) -> bool {
+    match text {
+        | "auto"
+        | "default"
+        | "union" => true,
+        _ => false,
+    }
+}
+
+fn find_reparsable_node<'node>(
+    node: SyntaxNodeRef<'node>,
+    range: TextRange,
+) -> Option<(SyntaxNodeRef<'node>, fn(&mut Parser))> {
+    let node = algo::find_covering_node(node, range);
+    return algo::ancestors(node)
+        .filter_map(|node| reparser(node).map(|r| (node, r)))
+        .next();
+
+    fn reparser(node: SyntaxNodeRef) -> Option<fn(&mut Parser)> {
+        let res = match node.kind() {
+            BLOCK => grammar::block,
+            NAMED_FIELD_DEF_LIST => grammar::named_field_def_list,
+            NAMED_FIELD_LIST => grammar::named_field_list,
+            ENUM_VARIANT_LIST => grammar::enum_variant_list,
+            MATCH_ARM_LIST => grammar::match_arm_list,
+            USE_TREE_LIST => grammar::use_tree_list,
+            EXTERN_ITEM_LIST => grammar::extern_item_list,
+            TOKEN_TREE if node.first_child().unwrap().kind() == L_CURLY => grammar::token_tree,
+            ITEM_LIST => {
+                let parent = node.parent().unwrap();
+                match parent.kind() {
+                    IMPL_ITEM => grammar::impl_item_list,
+                    TRAIT_DEF => grammar::trait_item_list,
+                    MODULE => grammar::mod_item_list,
+                    _ => return None,
+                }
+            }
+            _ => return None,
+        };
+        Some(res)
+    }
+}
+
+fn is_balanced(tokens: &[Token]) -> bool {
+    if tokens.len() == 0
+        || tokens.first().unwrap().kind != L_CURLY
+        || tokens.last().unwrap().kind != R_CURLY {
+        return false;
+    }
+    let mut balance = 0usize;
+    for t in tokens.iter() {
+        match t.kind {
+            L_CURLY => balance += 1,
+            R_CURLY => balance = match balance.checked_sub(1) {
+                Some(b) => b,
+                None => return false,
+            },
+            _ => (),
+        }
+    }
+    balance == 0
+}
+
+fn merge_errors(
+    old_errors: Vec<SyntaxError>,
+    new_errors: Vec<SyntaxError>,
+    old_node: SyntaxNodeRef,
+    edit: &AtomEdit,
+) -> Vec<SyntaxError> {
+    let mut res = Vec::new();
+    for e in old_errors {
+        if e.offset <= old_node.range().start() {
+            res.push(e)
+        } else if e.offset >= old_node.range().end() {
+            res.push(SyntaxError {
+                msg: e.msg,
+                offset: e.offset + TextUnit::of_str(&edit.insert) - edit.delete.len(),
+            })
+        }
+    }
+    for e in new_errors {
+        res.push(SyntaxError {
+            msg: e.msg,
+            offset: e.offset + old_node.range().start(),
+        })
+    }
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{
+        super::{
+            File,
+            test_utils::extract_range,
+            text_utils::replace_range,
+            utils::dump_tree,
+        },
+        reparse_leaf, reparse_block, AtomEdit, GreenNode, SyntaxError, SyntaxNodeRef,
+    };
+
+    fn do_check<F>(
+        before: &str,
+        replace_with: &str,
+        reparser: F,
+    ) where
+        for<'a> F: Fn(
+            SyntaxNodeRef<'a>,
+            &AtomEdit,
+        ) -> Option<(SyntaxNodeRef<'a>, GreenNode, Vec<SyntaxError>)>
+    {
+        let (range, before) = extract_range(before);
+        let after = replace_range(before.clone(), range, replace_with);
+
+        let fully_reparsed = File::parse(&after);
+        let incrementally_reparsed = {
+            let f = File::parse(&before);
+            let edit = AtomEdit { delete: range, insert: replace_with.to_string() };
+            let (node, green, new_errors) =
+                reparser(f.syntax(), &edit).expect("cannot incrementally reparse");
+            let green_root = node.replace_with(green);
+            let errors = super::merge_errors(f.errors(), new_errors, node, &edit);
+            File::new(green_root, errors)
+        };
+
+        assert_eq_text!(
+            &dump_tree(fully_reparsed.syntax()),
+            &dump_tree(incrementally_reparsed.syntax()),
+        )
+    }
+
+    #[test]
+    fn reparse_block_tests() {
+        let do_check = |before, replace_to|
+            do_check(before, replace_to, reparse_block);
+
+        do_check(r"
+fn foo() {
+    let x = foo + <|>bar<|>
+}
+", "baz");
+        do_check(r"
+fn foo() {
+    let x = foo<|> + bar<|>
+}
+", "baz");
+        do_check(r"
+struct Foo {
+    f: foo<|><|>
+}
+", ",\n    g: (),");
+        do_check(r"
+fn foo {
+    let;
+    1 + 1;
+    <|>92<|>;
+}
+", "62");
+        do_check(r"
+mod foo {
+    fn <|><|>
+}
+", "bar");
+        do_check(r"
+trait Foo {
+    type <|>Foo<|>;
+}
+", "Output");
+        do_check(r"
+impl IntoIterator<Item=i32> for Foo {
+    f<|><|>
+}
+", "n next(");
+        do_check(r"
+use a::b::{foo,<|>,bar<|>};
+    ", "baz");
+        do_check(r"
+pub enum A {
+    Foo<|><|>
+}
+", "\nBar;\n");
+        do_check(r"
+foo!{a, b<|><|> d}
+", ", c[3]");
+        do_check(r"
+fn foo() {
+    vec![<|><|>]
+}
+", "123");
+        do_check(r"
+extern {
+    fn<|>;<|>
+}
+", " exit(code: c_int)");
+    }
+
+    #[test]
+    fn reparse_leaf_tests() {
+        let do_check = |before, replace_to|
+            do_check(before, replace_to, reparse_leaf);
+
+        do_check(r"<|><|>
+fn foo() -> i32 { 1 }
+", "\n\n\n   \n");
+        do_check(r"
+fn foo() -> <|><|> {}
+", "  \n");
+        do_check(r"
+fn <|>foo<|>() -> i32 { 1 }
+", "bar");
+        do_check(r"
+fn foo<|><|>foo() {  }
+", "bar");
+        do_check(r"
+fn foo /* <|><|> */ () {}
+", "some comment");
+        do_check(r"
+fn baz <|><|> () {}
+", "    \t\t\n\n");
+        do_check(r"
+fn baz <|><|> () {}
+", "    \t\t\n\n");
+        do_check(r"
+/// foo <|><|>omment
+mod { }
+", "c");
+        do_check(r#"
+fn -> &str { "Hello<|><|>" }
+"#, ", world");
+        do_check(r#"
+fn -> &str { // "Hello<|><|>"
+"#, ", world");
+        do_check(r##"
+fn -> &str { r#"Hello<|><|>"#
+"##, ", world");
+        do_check(r"
+#[derive(<|>Copy<|>)]
+enum Foo {
+
+}
+", "Clone");
+    }
+}
\ No newline at end of file
diff --git a/crates/libsyntax2/src/text_utils.rs b/crates/libsyntax2/src/text_utils.rs
index e3d73888f..58ae1e43e 100644
--- a/crates/libsyntax2/src/text_utils.rs
+++ b/crates/libsyntax2/src/text_utils.rs
@@ -17,3 +17,10 @@ pub fn intersect(r1: TextRange, r2: TextRange) -> Option<TextRange> {
         None
     }
 }
+
+pub fn replace_range(mut text: String, range: TextRange, replace_with: &str) -> String {
+    let start = u32::from(range.start()) as usize;
+    let end = u32::from(range.end()) as usize;
+    text.replace_range(start..end, replace_with);
+    text
+}
\ No newline at end of file