10 files changed, 190 insertions, 9 deletions

diff --git a/README.md b/README.md
index 979e4ef88..deaa147ba 100644
--- a/README.md
+++ b/README.md
@@ -58,7 +58,7 @@ https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Frls-2.2E0
 ## Quick Links
 
 * API docs: https://rust-analyzer.github.io/rust-analyzer/ra_ide/
-
+* Website: https://rust-analyzer.github.io/
 
 ## License
 
diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index af42854cc..98ba05fc2 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -32,6 +32,7 @@ use hir_def::{
 use hir_expand::{diagnostics::DiagnosticSink, name::name};
 use ra_arena::map::ArenaMap;
 use ra_prof::profile;
+use test_utils::tested_by;
 
 use super::{
     primitive::{FloatTy, IntTy},
@@ -274,6 +275,29 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         self.normalize_associated_types_in(ty)
     }
 
+    /// Replaces `impl Trait` in `ty` by type variables and obligations for
+    /// those variables. This is done for function arguments when calling a
+    /// function, and for return types when inside the function body, i.e. in
+    /// the cases where the `impl Trait` is 'transparent'. In other cases, `impl
+    /// Trait` is represented by `Ty::Opaque`.
+    fn insert_vars_for_impl_trait(&mut self, ty: Ty) -> Ty {
+        ty.fold(&mut |ty| match ty {
+            Ty::Opaque(preds) => {
+                tested_by!(insert_vars_for_impl_trait);
+                let var = self.table.new_type_var();
+                let var_subst = Substs::builder(1).push(var.clone()).build();
+                self.obligations.extend(
+                    preds
+                        .iter()
+                        .map(|pred| pred.clone().subst_bound_vars(&var_subst))
+                        .filter_map(Obligation::from_predicate),
+                );
+                var
+            }
+            _ => ty,
+        })
+    }
+
     /// Replaces Ty::Unknown by a new type var, so we can maybe still infer it.
     fn insert_type_vars_shallow(&mut self, ty: Ty) -> Ty {
         match ty {
@@ -414,7 +438,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
             self.infer_pat(*pat, &ty, BindingMode::default());
         }
-        self.return_ty = self.make_ty(&data.ret_type);
+        let return_ty = self.make_ty(&data.ret_type);
+        self.return_ty = self.insert_vars_for_impl_trait(return_ty);
     }
 
     fn infer_body(&mut self) {
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index 2e3cdd53a..924ad3e81 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -613,6 +613,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                     continue;
                 }
 
+                let param_ty = self.insert_vars_for_impl_trait(param_ty);
                 let param_ty = self.normalize_associated_types_in(param_ty);
                 self.infer_expr_coerce(arg, &Expectation::has_type(param_ty.clone()));
             }
diff --git a/crates/ra_hir_ty/src/marks.rs b/crates/ra_hir_ty/src/marks.rs
index 0f754eb9c..fe74acf11 100644
--- a/crates/ra_hir_ty/src/marks.rs
+++ b/crates/ra_hir_ty/src/marks.rs
@@ -6,4 +6,5 @@ test_utils::marks!(
     type_var_resolves_to_int_var
     match_ergonomics_ref
     coerce_merge_fail_fallback
+    insert_vars_for_impl_trait
 );
diff --git a/crates/ra_hir_ty/src/tests/traits.rs b/crates/ra_hir_ty/src/tests/traits.rs
index 6139adb72..802937cb0 100644
--- a/crates/ra_hir_ty/src/tests/traits.rs
+++ b/crates/ra_hir_ty/src/tests/traits.rs
@@ -1,7 +1,10 @@
-use super::{infer, type_at, type_at_pos};
-use crate::test_db::TestDB;
 use insta::assert_snapshot;
+
 use ra_db::fixture::WithFixture;
+use test_utils::covers;
+
+use super::{infer, infer_with_mismatches, type_at, type_at_pos};
+use crate::test_db::TestDB;
 
 #[test]
 fn infer_await() {
@@ -1486,3 +1489,61 @@ fn test<T, U>() where T: Trait<U::Item>, U: Trait<T::Item> {
     // this is a legitimate cycle
     assert_eq!(t, "{unknown}");
 }
+
+#[test]
+fn unify_impl_trait() {
+    covers!(insert_vars_for_impl_trait);
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+trait Trait<T> {}
+
+fn foo(x: impl Trait<u32>) { loop {} }
+fn bar<T>(x: impl Trait<T>) -> T { loop {} }
+
+struct S<T>(T);
+impl<T> Trait<T> for S<T> {}
+
+fn default<T>() -> T { loop {} }
+
+fn test() -> impl Trait<i32> {
+    let s1 = S(default());
+    foo(s1);
+    let x: i32 = bar(S(default()));
+    S(default())
+}
+"#, true),
+        @r###"
+    [27; 28) 'x': impl Trait<u32>
+    [47; 58) '{ loop {} }': ()
+    [49; 56) 'loop {}': !
+    [54; 56) '{}': ()
+    [69; 70) 'x': impl Trait<T>
+    [92; 103) '{ loop {} }': T
+    [94; 101) 'loop {}': !
+    [99; 101) '{}': ()
+    [172; 183) '{ loop {} }': T
+    [174; 181) 'loop {}': !
+    [179; 181) '{}': ()
+    [214; 310) '{     ...t()) }': S<i32>
+    [224; 226) 's1': S<u32>
+    [229; 230) 'S': S<u32>(T) -> S<T>
+    [229; 241) 'S(default())': S<u32>
+    [231; 238) 'default': fn default<u32>() -> T
+    [231; 240) 'default()': u32
+    [247; 250) 'foo': fn foo(impl Trait<u32>) -> ()
+    [247; 254) 'foo(s1)': ()
+    [251; 253) 's1': S<u32>
+    [264; 265) 'x': i32
+    [273; 276) 'bar': fn bar<i32>(impl Trait<T>) -> T
+    [273; 290) 'bar(S(...lt()))': i32
+    [277; 278) 'S': S<i32>(T) -> S<T>
+    [277; 289) 'S(default())': S<i32>
+    [279; 286) 'default': fn default<i32>() -> T
+    [279; 288) 'default()': i32
+    [296; 297) 'S': S<i32>(T) -> S<T>
+    [296; 308) 'S(default())': S<i32>
+    [298; 305) 'default': fn default<i32>() -> T
+    [298; 307) 'default()': i32
+    "###
+    );
+}
diff --git a/crates/ra_parser/src/grammar/expressions/atom.rs b/crates/ra_parser/src/grammar/expressions/atom.rs
index f06191963..09f0a2d98 100644
--- a/crates/ra_parser/src/grammar/expressions/atom.rs
+++ b/crates/ra_parser/src/grammar/expressions/atom.rs
@@ -248,7 +248,12 @@ fn lambda_expr(p: &mut Parser) -> CompletedMarker {
             p.error("expected `{`");
         }
     }
-    expr(p);
+
+    if p.at_ts(EXPR_FIRST) {
+        expr(p);
+    } else {
+        p.error("expected expression");
+    }
     m.complete(p, LAMBDA_EXPR)
 }
 
diff --git a/crates/ra_syntax/test_data/parser/err/0039_lambda_recovery.rs b/crates/ra_syntax/test_data/parser/err/0039_lambda_recovery.rs
new file mode 100644
index 000000000..a2f74bd87
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/err/0039_lambda_recovery.rs
@@ -0,0 +1,5 @@
+fn foo() -> i32 {
+    [1, 2, 3].iter()
+        .map(|it|)
+        .max::<i32>();
+}
diff --git a/crates/ra_syntax/test_data/parser/err/0039_lambda_recovery.txt b/crates/ra_syntax/test_data/parser/err/0039_lambda_recovery.txt
new file mode 100644
index 000000000..d1544634c
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/err/0039_lambda_recovery.txt
@@ -0,0 +1,83 @@
+SOURCE_FILE@[0; 83)
+  FN_DEF@[0; 82)
+    FN_KW@[0; 2) "fn"
+    WHITESPACE@[2; 3) " "
+    NAME@[3; 6)
+      IDENT@[3; 6) "foo"
+    PARAM_LIST@[6; 8)
+      L_PAREN@[6; 7) "("
+      R_PAREN@[7; 8) ")"
+    WHITESPACE@[8; 9) " "
+    RET_TYPE@[9; 15)
+      THIN_ARROW@[9; 11) "->"
+      WHITESPACE@[11; 12) " "
+      PATH_TYPE@[12; 15)
+        PATH@[12; 15)
+          PATH_SEGMENT@[12; 15)
+            NAME_REF@[12; 15)
+              IDENT@[12; 15) "i32"
+    WHITESPACE@[15; 16) " "
+    BLOCK_EXPR@[16; 82)
+      BLOCK@[16; 82)
+        L_CURLY@[16; 17) "{"
+        WHITESPACE@[17; 22) "\n    "
+        EXPR_STMT@[22; 80)
+          METHOD_CALL_EXPR@[22; 79)
+            METHOD_CALL_EXPR@[22; 57)
+              METHOD_CALL_EXPR@[22; 38)
+                ARRAY_EXPR@[22; 31)
+                  L_BRACK@[22; 23) "["
+                  LITERAL@[23; 24)
+                    INT_NUMBER@[23; 24) "1"
+                  COMMA@[24; 25) ","
+                  WHITESPACE@[25; 26) " "
+                  LITERAL@[26; 27)
+                    INT_NUMBER@[26; 27) "2"
+                  COMMA@[27; 28) ","
+                  WHITESPACE@[28; 29) " "
+                  LITERAL@[29; 30)
+                    INT_NUMBER@[29; 30) "3"
+                  R_BRACK@[30; 31) "]"
+                DOT@[31; 32) "."
+                NAME_REF@[32; 36)
+                  IDENT@[32; 36) "iter"
+                ARG_LIST@[36; 38)
+                  L_PAREN@[36; 37) "("
+                  R_PAREN@[37; 38) ")"
+              WHITESPACE@[38; 47) "\n        "
+              DOT@[47; 48) "."
+              NAME_REF@[48; 51)
+                IDENT@[48; 51) "map"
+              ARG_LIST@[51; 57)
+                L_PAREN@[51; 52) "("
+                LAMBDA_EXPR@[52; 56)
+                  PARAM_LIST@[52; 56)
+                    PIPE@[52; 53) "|"
+                    PARAM@[53; 55)
+                      BIND_PAT@[53; 55)
+                        NAME@[53; 55)
+                          IDENT@[53; 55) "it"
+                    PIPE@[55; 56) "|"
+                R_PAREN@[56; 57) ")"
+            WHITESPACE@[57; 66) "\n        "
+            DOT@[66; 67) "."
+            NAME_REF@[67; 70)
+              IDENT@[67; 70) "max"
+            TYPE_ARG_LIST@[70; 77)
+              COLONCOLON@[70; 72) "::"
+              L_ANGLE@[72; 73) "<"
+              TYPE_ARG@[73; 76)
+                PATH_TYPE@[73; 76)
+                  PATH@[73; 76)
+                    PATH_SEGMENT@[73; 76)
+                      NAME_REF@[73; 76)
+                        IDENT@[73; 76) "i32"
+              R_ANGLE@[76; 77) ">"
+            ARG_LIST@[77; 79)
+              L_PAREN@[77; 78) "("
+              R_PAREN@[78; 79) ")"
+          SEMI@[79; 80) ";"
+        WHITESPACE@[80; 81) "\n"
+        R_CURLY@[81; 82) "}"
+  WHITESPACE@[82; 83) "\n"
+error 56: expected expression
diff --git a/editors/code/package.json b/editors/code/package.json
index df8e9eecb..f7ab2c2f3 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -219,7 +219,7 @@
                 },
                 "rust-analyzer.useClientWatching": {
                     "type": "boolean",
-                    "default": false,
+                    "default": true,
                     "description": "client provided file watching instead of notify watching."
                 },
                 "rust-analyzer.cargo-watch.arguments": {
@@ -529,7 +529,7 @@
             },
             {
                 "id": "ralsp.type.lifetime",
-                "description": "Color for `Self` param type",
+                "description": "Color for lifetimes parameters",
                 "defaults": {
                     "dark": "#4EC9B0",
                     "light": "#267F99",
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index a6e0f6454..e131f09df 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -31,7 +31,7 @@ export class Config {
     public displayInlayHints = true;
     public maxInlayHintLength: null | number = null;
     public excludeGlobs = [];
-    public useClientWatching = false;
+    public useClientWatching = true;
     public featureFlags = {};
     // for internal use
     public withSysroot: null | boolean = null;
@@ -157,7 +157,7 @@ export class Config {
             this.excludeGlobs = config.get('excludeGlobs') || [];
         }
         if (config.has('useClientWatching')) {
-            this.useClientWatching = config.get('useClientWatching') || false;
+            this.useClientWatching = config.get('useClientWatching') || true;
         }
         if (config.has('featureFlags')) {
             this.featureFlags = config.get('featureFlags') || {};