7 files changed, 73 insertions, 10 deletions

diff --git a/crates/ra_analysis/src/descriptors/mod.rs b/crates/ra_analysis/src/descriptors/mod.rs
index 873eb47e4..0220f7d5d 100644
--- a/crates/ra_analysis/src/descriptors/mod.rs
+++ b/crates/ra_analysis/src/descriptors/mod.rs
@@ -2,7 +2,6 @@ pub(crate) mod module;
 
 use ra_syntax::{
     ast::{self, AstNode, NameOwner},
-    text_utils::is_subrange,
 };
 
 #[derive(Debug, Clone)]
@@ -23,7 +22,7 @@ impl FnDescriptor {
             let label: String = node
                 .syntax()
                 .children()
-                .filter(|child| !is_subrange(body_range, child.range()))
+                .filter(|child| !child.range().is_subrange(&body_range))
                 .map(|node| node.text().to_string())
                 .collect();
             label
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index a67cac21e..363c72c0b 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -12,6 +12,7 @@ mod descriptors;
 mod imp;
 mod symbol_index;
 mod completion;
+mod syntax_ptr;
 
 use std::{
     fmt,
diff --git a/crates/ra_analysis/src/syntax_ptr.rs b/crates/ra_analysis/src/syntax_ptr.rs
new file mode 100644
index 000000000..863ad2672
--- /dev/null
+++ b/crates/ra_analysis/src/syntax_ptr.rs
@@ -0,0 +1,67 @@
+use ra_syntax::{
+    File, TextRange, SyntaxKind, SyntaxNode, SyntaxNodeRef,
+    ast::{self, AstNode},
+};
+
+use crate::FileId;
+use crate::db::SyntaxDatabase;
+
+/// SyntaxPtr is a cheap `Copy` id which identifies a particular syntax node,
+/// without retainig syntax tree in memory. You need to explicitelly `resovle`
+/// `SyntaxPtr` to get a `SyntaxNode`
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) struct SyntaxPtr {
+    file_id: FileId,
+    local: LocalSyntaxPtr,
+}
+
+impl SyntaxPtr {
+    pub(crate) fn new(file_id: FileId, node: SyntaxNodeRef) -> SyntaxPtr {
+        let local = LocalSyntaxPtr::new(node);
+        SyntaxPtr { file_id, local }
+    }
+
+    pub(crate) fn resolve(self, db: &impl SyntaxDatabase) -> SyntaxNode {
+        let syntax = db.file_syntax(self.file_id);
+        self.local.resolve(&syntax)
+    }
+}
+
+
+/// A pionter to a syntax node inside a file.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+struct LocalSyntaxPtr {
+    range: TextRange,
+    kind: SyntaxKind,
+}
+
+impl LocalSyntaxPtr {
+    fn new(node: SyntaxNodeRef) -> LocalSyntaxPtr {
+        LocalSyntaxPtr {
+            range: node.range(),
+            kind: node.kind(),
+        }
+    }
+
+    fn resolve(self, file: &File) -> SyntaxNode {
+        let mut curr = file.syntax();
+        loop {
+            if curr.range() == self.range && curr.kind() == self.kind {
+                return curr.owned();
+            }
+            curr = curr.children()
+                .find(|it| self.range.is_subrange(&it.range()))
+                .unwrap_or_else(|| panic!("can't resovle local ptr to SyntaxNode: {:?}", self))
+        }
+    }
+}
+
+
+#[test]
+fn test_local_syntax_ptr() {
+    let file = File::parse("struct Foo { f: u32, }");
+    let field = file.syntax().descendants().find_map(ast::NamedFieldDef::cast).unwrap();
+    let ptr = LocalSyntaxPtr::new(field.syntax());
+    let field_syntax = ptr.resolve(&file);
+    assert_eq!(field.syntax(), field_syntax);
+}
diff --git a/crates/ra_editor/src/completion.rs b/crates/ra_editor/src/completion.rs
index 0a3675255..a0b168bc6 100644
--- a/crates/ra_editor/src/completion.rs
+++ b/crates/ra_editor/src/completion.rs
@@ -3,7 +3,6 @@ use rustc_hash::{FxHashMap, FxHashSet};
 use ra_syntax::{
     algo::visit::{visitor, visitor_ctx, Visitor, VisitorCtx},
     ast::{self, AstChildren, LoopBodyOwner, ModuleItemOwner},
-    text_utils::is_subrange,
     AstNode, File,
     SyntaxKind::*,
     SyntaxNodeRef, TextUnit,
@@ -191,7 +190,7 @@ fn is_in_loop_body(name_ref: ast::NameRef) -> bool {
             .visit::<ast::LoopExpr, _>(LoopBodyOwner::loop_body)
             .accept(node);
         if let Some(Some(body)) = loop_body {
-            if is_subrange(body.syntax().range(), name_ref.syntax().range()) {
+            if name_ref.syntax().range().is_subrange(&body.syntax().range()) {
                 return true;
             }
         }
diff --git a/crates/ra_syntax/Cargo.toml b/crates/ra_syntax/Cargo.toml
index 7efebab8b..043c9bacd 100644
--- a/crates/ra_syntax/Cargo.toml
+++ b/crates/ra_syntax/Cargo.toml
@@ -11,6 +11,7 @@ itertools = "0.7.8"
 drop_bomb = "0.1.4"
 parking_lot = "0.6.0"
 rowan = "0.1.1"
+text_unit = "0.1.5"
 
 [dev-dependencies]
 test_utils = { path = "../test_utils" }
diff --git a/crates/ra_syntax/src/algo/mod.rs b/crates/ra_syntax/src/algo/mod.rs
index d82c42b3e..f92529d3e 100644
--- a/crates/ra_syntax/src/algo/mod.rs
+++ b/crates/ra_syntax/src/algo/mod.rs
@@ -2,7 +2,7 @@ pub mod visit;
 // pub mod walk;
 
 use crate::{
-    text_utils::{contains_offset_nonstrict, is_subrange},
+    text_utils::{contains_offset_nonstrict},
     SyntaxNodeRef, TextRange, TextUnit,
 };
 
@@ -91,7 +91,7 @@ impl<'f> Iterator for LeafAtOffset<'f> {
 
 pub fn find_covering_node(root: SyntaxNodeRef, range: TextRange) -> SyntaxNodeRef {
     assert!(
-        is_subrange(root.range(), range),
+        range.is_subrange(&root.range()),
         "node range: {:?}, target range: {:?}",
         root.range(),
         range,
diff --git a/crates/ra_syntax/src/text_utils.rs b/crates/ra_syntax/src/text_utils.rs
index abda5ec39..a90f8a083 100644
--- a/crates/ra_syntax/src/text_utils.rs
+++ b/crates/ra_syntax/src/text_utils.rs
@@ -4,10 +4,6 @@ pub fn contains_offset_nonstrict(range: TextRange, offset: TextUnit) -> bool {
     range.start() <= offset && offset <= range.end()
 }
 
-pub fn is_subrange(range: TextRange, subrange: TextRange) -> bool {
-    range.start() <= subrange.start() && subrange.end() <= range.end()
-}
-
 pub fn intersect(r1: TextRange, r2: TextRange) -> Option<TextRange> {
     let start = r1.start().max(r2.start());
     let end = r1.end().min(r2.end());