3 files changed, 96 insertions, 1 deletions

diff --git a/crates/ra_hir/src/ty/autoderef.rs b/crates/ra_hir/src/ty/autoderef.rs
new file mode 100644
index 000000000..24a386558
--- /dev/null
+++ b/crates/ra_hir/src/ty/autoderef.rs
@@ -0,0 +1,21 @@
+//! In certain situations, rust automatically inserts derefs as necessary: For
+//! example, field accesses `foo.bar` still work when `foo` is actually a
+//! reference to a type with the field `bar`. This is an approximation of the
+//! logic in rustc (which lives in librustc_typeck/check/autoderef.rs).
+
+use ra_syntax::algo::generate;
+
+use crate::HirDatabase;
+use super::Ty;
+
+impl Ty {
+    /// Iterates over the possible derefs of `ty`.
+    pub fn autoderef<'a>(self, db: &'a impl HirDatabase) -> impl Iterator<Item = Ty> + 'a {
+        generate(Some(self), move |ty| ty.autoderef_step(db))
+    }
+
+    fn autoderef_step(&self, _db: &impl HirDatabase) -> Option<Ty> {
+        // TODO Deref::deref
+        self.builtin_deref()
+    }
+}
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index 83aedaa00..e6c7e225b 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -95,7 +95,7 @@ fn test() {
 }
 
 #[test]
-fn infer_refs_and_ptrs() {
+fn infer_refs() {
     check_inference(
         r#"
 fn test(a: &u32, b: &mut u32, c: *const u32, d: *mut u32) {
@@ -180,6 +180,37 @@ fn test() {
     );
 }
 
+#[test]
+fn infer_field_autoderef() {
+    check_inference(
+        r#"
+struct A {
+    b: B,
+}
+struct B;
+
+fn test1(a: A) {
+    let a1 = a;
+    a1.b;
+    let a2 = &a;
+    a2.b;
+    let a3 = &mut a;
+    a3.b;
+    let a4 = &&&&&&&a;
+    a4.b;
+    let a5 = &mut &&mut &&mut a;
+    a5.b;
+}
+
+fn test2(a1: *const A, a2: *mut A) {
+    a1.b;
+    a2.b;
+}
+"#,
+        "field_autoderef.txt",
+    );
+}
+
 fn infer(content: &str) -> String {
     let (db, _, file_id) = MockDatabase::with_single_file(content);
     let source_file = db.source_file(file_id);
diff --git a/crates/ra_hir/src/ty/tests/data/field_autoderef.txt b/crates/ra_hir/src/ty/tests/data/field_autoderef.txt
new file mode 100644
index 000000000..e1db1db40
--- /dev/null
+++ b/crates/ra_hir/src/ty/tests/data/field_autoderef.txt
@@ -0,0 +1,43 @@
+[44; 45) 'a': A
+[50; 213) '{     ...5.b; }': ()
+[60; 62) 'a1': A
+[65; 66) 'a': A
+[72; 74) 'a1': A
+[72; 76) 'a1.b': B
+[86; 88) 'a2': &A
+[91; 93) '&a': &A
+[92; 93) 'a': A
+[99; 101) 'a2': &A
+[99; 103) 'a2.b': B
+[113; 115) 'a3': &mut A
+[118; 124) '&mut a': &mut A
+[123; 124) 'a': A
+[130; 132) 'a3': &mut A
+[130; 134) 'a3.b': B
+[144; 146) 'a4': &&&&&&&A
+[149; 157) '&&&&&&&a': &&&&&&&A
+[150; 157) '&&&&&&a': &&&&&&A
+[151; 157) '&&&&&a': &&&&&A
+[152; 157) '&&&&a': &&&&A
+[153; 157) '&&&a': &&&A
+[154; 157) '&&a': &&A
+[155; 157) '&a': &A
+[156; 157) 'a': A
+[163; 165) 'a4': &&&&&&&A
+[163; 167) 'a4.b': B
+[177; 179) 'a5': &mut &&mut &&mut A
+[182; 200) '&mut &...&mut a': &mut &&mut &&mut A
+[187; 200) '&&mut &&mut a': &&mut &&mut A
+[188; 200) '&mut &&mut a': &mut &&mut A
+[193; 200) '&&mut a': &&mut A
+[194; 200) '&mut a': &mut A
+[199; 200) 'a': A
+[206; 208) 'a5': &mut &&mut &&mut A
+[206; 210) 'a5.b': B
+[224; 226) 'a1': *const A
+[238; 240) 'a2': *mut A
+[250; 273) '{     ...2.b; }': ()
+[256; 258) 'a1': *const A
+[256; 260) 'a1.b': B
+[266; 268) 'a2': *mut A
+[266; 270) 'a2.b': B