29 files changed, 299 insertions, 336 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 6f8a4431d..0206f16bc 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -108,8 +108,8 @@ version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_derive 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.41 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -171,7 +171,7 @@ dependencies = [
  "chalk-macros 0.1.1 (git+https://github.com/rust-lang/chalk.git?rev=1e5c1929364dfbb7c0c7ac0956b8250abe7c2cae)",
  "chalk-rust-ir 0.1.0 (git+https://github.com/rust-lang/chalk.git?rev=1e5c1929364dfbb7c0c7ac0956b8250abe7c2cae)",
  "ena 0.13.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itertools 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "petgraph 0.4.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -288,7 +288,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -413,7 +413,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "getrandom"
-version = "0.1.12"
+version = "0.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -501,7 +501,7 @@ dependencies = [
  "console 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "difference 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.41 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_yaml 0.8.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "uuid 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -517,7 +517,7 @@ dependencies = [
 
 [[package]]
 name = "itertools"
-version = "0.8.0"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "either 1.5.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -624,7 +624,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "crossbeam-channel 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.41 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -634,7 +634,7 @@ version = "0.61.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.41 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_repr 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -811,7 +811,7 @@ dependencies = [
  "proc-macro-hack 0.5.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -845,7 +845,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -903,7 +903,7 @@ name = "ra_assists"
 version = "0.1.0"
 dependencies = [
  "format-buf 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itertools 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "join_to_string 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_db 0.1.0",
  "ra_fmt 0.1.0",
@@ -970,7 +970,7 @@ dependencies = [
 name = "ra_fmt"
 version = "0.1.0"
 dependencies = [
- "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itertools 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_syntax 0.1.0",
 ]
 
@@ -1007,7 +1007,7 @@ dependencies = [
  "format-buf 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "fst 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "insta 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itertools 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "join_to_string 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1049,7 +1049,7 @@ dependencies = [
  "ra_vfs_glob 0.1.0",
  "relative-path 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.41 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "test_utils 0.1.0",
@@ -1081,7 +1081,7 @@ name = "ra_prof"
 version = "0.1.0"
 dependencies = [
  "backtrace 0.3.40 (registry+https://github.com/rust-lang/crates.io-index)",
- "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itertools 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "jemalloc-ctl 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "jemallocator 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1097,7 +1097,7 @@ dependencies = [
  "ra_cfg 0.1.0",
  "ra_db 0.1.0",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.41 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1106,7 +1106,7 @@ name = "ra_syntax"
 version = "0.1.0"
 dependencies = [
  "arrayvec 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "itertools 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "once_cell 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_parser 0.1.0",
  "ra_text_edit 0.1.0",
@@ -1180,7 +1180,7 @@ name = "rand"
 version = "0.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "getrandom 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "getrandom 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.65 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_chacha 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1224,7 +1224,7 @@ name = "rand_core"
 version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "getrandom 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "getrandom 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1370,7 +1370,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "base64 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1441,7 +1441,7 @@ dependencies = [
  "heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1463,7 +1463,7 @@ version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1473,20 +1473,20 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "serde"
-version = "1.0.101"
+version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "serde_derive 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.101"
+version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1496,7 +1496,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "itoa 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "ryu 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1506,7 +1506,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1516,7 +1516,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "dtoa 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "linked-hash-map 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "yaml-rust 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1535,7 +1535,7 @@ name = "smol_str"
 version = "0.1.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1557,7 +1557,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "syn"
-version = "1.0.5"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1673,7 +1673,7 @@ dependencies = [
  "idna 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "matches 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "percent-encoding 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1682,7 +1682,7 @@ version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "rand 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1759,7 +1759,7 @@ dependencies = [
  "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "ron 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)",
  "walkdir 2.2.9 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1828,7 +1828,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
 "checksum fuchsia-zircon 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2e9763c69ebaae630ba35f74888db465e49e259ba1bc0eda7d06f4a067615d82"
 "checksum fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
-"checksum getrandom 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)" = "473a1265acc8ff1e808cd0a1af8cee3c2ee5200916058a2ca113c29f2d903571"
+"checksum getrandom 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "e7db7ca94ed4cd01190ceee0d8a8052f08a247aa1b469a7f68c6a3b71afcf407"
 "checksum glob 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9b919933a397b79c37e33b77bb2aa3dc8eb6e165ad809e58ff75bc7db2e34574"
 "checksum globset 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "925aa2cac82d8834e2b2a4415b6f6879757fb5c0928fc445ae76461a12eed8f2"
 "checksum heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20564e78d53d2bb135c343b3f47714a56af2061f1c928fdb541dc7b9fdd94205"
@@ -1839,7 +1839,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum inotify-sys 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "e74a1aa87c59aeff6ef2cc2fa62d41bc43f54952f55652656b18a02fd5e356c0"
 "checksum insta 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0d499dc062e841590a67230d853bce62d0abeb91304927871670b7c55c461349"
 "checksum iovec 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "b2b3ea6ff95e175473f8ffe6a7eb7c00d054240321b84c57051175fe3c1e075e"
-"checksum itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5b8467d9c1cebe26feb08c640139247fac215782d35371ade9a2136ed6085358"
+"checksum itertools 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "87fa75c9dea7b07be3138c49abbb83fd4bea199b5cdc76f9804458edc5da0d6e"
 "checksum itoa 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "501266b7edd0174f8530248f87f99c88fbe60ca4ef3dd486835b8d8d53136f7f"
 "checksum jemalloc-ctl 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c502a5ff9dd2924f1ed32ba96e3b65735d837b4bfd978d3161b1702e66aca4b7"
 "checksum jemalloc-sys 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0d3b9f3f5c9b31aa0f5ed3260385ac205db665baa41d49bb8338008ae94ede45"
@@ -1922,8 +1922,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum scopeguard 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b42e15e59b18a828bbf5c58ea01debb36b9b096346de35d941dcb89009f24a0d"
 "checksum semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
-"checksum serde 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)" = "9796c9b7ba2ffe7a9ce53c2287dfc48080f4b2b362fcc245a259b3a7201119dd"
-"checksum serde_derive 1.0.101 (registry+https://github.com/rust-lang/crates.io-index)" = "4b133a43a1ecd55d4086bd5b4dc6c1751c68b1bfbeba7a5040442022c7e7c02e"
+"checksum serde 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)" = "0c4b39bd9b0b087684013a792c59e3e07a46a01d2322518d8a1104641a0b1be0"
+"checksum serde_derive 1.0.102 (registry+https://github.com/rust-lang/crates.io-index)" = "ca13fc1a832f793322228923fbb3aba9f3f44444898f835d31ad1b74fa0a2bf8"
 "checksum serde_json 1.0.41 (registry+https://github.com/rust-lang/crates.io-index)" = "2f72eb2a68a7dc3f9a691bfda9305a1c017a6215e5a4545c258500d2099a37c2"
 "checksum serde_repr 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "cd02c7587ec314570041b2754829f84d873ced14a96d1fd1823531e11db40573"
 "checksum serde_yaml 0.8.11 (registry+https://github.com/rust-lang/crates.io-index)" = "691b17f19fc1ec9d94ec0b5864859290dff279dbd7b03f017afda54eb36c3c35"
@@ -1932,7 +1932,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum smol_str 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)" = "34836c9a295c62c2ce3514471117c5cb269891e8421b2aafdd910050576c4d8b"
 "checksum stacker 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "d96fc4f13a0ac088e9a3cd9af1cc8c5cc1ab5deb2145cef661267dfc9c542f8a"
 "checksum superslice 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ab16ced94dbd8a46c82fd81e3ed9a8727dac2977ea869d217bcc4ea1f122e81f"
-"checksum syn 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "66850e97125af79138385e9b88339cbcd037e3f28ceab8c5ad98e64f0f1f80bf"
+"checksum syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)" = "0e7bedb3320d0f3035594b0b723c8a28d7d336a3eda3881db79e61d676fb644c"
 "checksum tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
 "checksum termios 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "72b620c5ea021d75a735c943269bb07d30c9b77d6ac6b236bc8b5c496ef05625"
 "checksum text_unit 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)" = "e08bbcb7a3adbda0eb23431206b653bdad3d8dea311e72d36bf2215e27a42579"
diff --git a/crates/ra_assists/src/assist_ctx.rs b/crates/ra_assists/src/assist_ctx.rs
index c52736679..1908bdec9 100644
--- a/crates/ra_assists/src/assist_ctx.rs
+++ b/crates/ra_assists/src/assist_ctx.rs
@@ -14,8 +14,8 @@ use crate::{AssistAction, AssistId, AssistLabel};
 
 #[derive(Clone, Debug)]
 pub(crate) enum Assist {
-    Unresolved(Vec<AssistLabel>),
-    Resolved(Vec<(AssistLabel, AssistAction)>),
+    Unresolved { label: AssistLabel },
+    Resolved { label: AssistLabel, action: AssistAction },
 }
 
 /// `AssistCtx` allows to apply an assist or check if it could be applied.
@@ -54,7 +54,6 @@ pub(crate) struct AssistCtx<'a, DB> {
     pub(crate) frange: FileRange,
     source_file: SourceFile,
     should_compute_edit: bool,
-    assist: Assist,
 }
 
 impl<'a, DB> Clone for AssistCtx<'a, DB> {
@@ -64,7 +63,6 @@ impl<'a, DB> Clone for AssistCtx<'a, DB> {
             frange: self.frange,
             source_file: self.source_file.clone(),
             should_compute_edit: self.should_compute_edit,
-            assist: self.assist.clone(),
         }
     }
 }
@@ -75,36 +73,30 @@ impl<'a, DB: HirDatabase> AssistCtx<'a, DB> {
         F: FnOnce(AssistCtx<DB>) -> T,
     {
         let parse = db.parse(frange.file_id);
-        let assist =
-            if should_compute_edit { Assist::Resolved(vec![]) } else { Assist::Unresolved(vec![]) };
 
-        let ctx = AssistCtx { db, frange, source_file: parse.tree(), should_compute_edit, assist };
+        let ctx = AssistCtx { db, frange, source_file: parse.tree(), should_compute_edit };
         f(ctx)
     }
 
-    pub(crate) fn add_action(
-        &mut self,
+    pub(crate) fn add_assist(
+        self,
         id: AssistId,
         label: impl Into<String>,
         f: impl FnOnce(&mut AssistBuilder),
-    ) -> &mut Self {
+    ) -> Option<Assist> {
         let label = AssistLabel { label: label.into(), id };
-        match &mut self.assist {
-            Assist::Unresolved(labels) => labels.push(label),
-            Assist::Resolved(labels_actions) => {
-                let action = {
-                    let mut edit = AssistBuilder::default();
-                    f(&mut edit);
-                    edit.build()
-                };
-                labels_actions.push((label, action));
-            }
-        }
-        self
-    }
-
-    pub(crate) fn build(self) -> Option<Assist> {
-        Some(self.assist)
+        let assist = if self.should_compute_edit {
+            let action = {
+                let mut edit = AssistBuilder::default();
+                f(&mut edit);
+                edit.build()
+            };
+            Assist::Resolved { label, action }
+        } else {
+            Assist::Unresolved { label }
+        };
+
+        Some(assist)
     }
 
     pub(crate) fn token_at_offset(&self) -> TokenAtOffset<SyntaxToken> {
diff --git a/crates/ra_assists/src/assists/add_derive.rs b/crates/ra_assists/src/assists/add_derive.rs
index d1e925b71..764b17bd8 100644
--- a/crates/ra_assists/src/assists/add_derive.rs
+++ b/crates/ra_assists/src/assists/add_derive.rs
@@ -25,10 +25,10 @@ use crate::{Assist, AssistCtx, AssistId};
 //     y: u32,
 // }
 // ```
-pub(crate) fn add_derive(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn add_derive(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let nominal = ctx.find_node_at_offset::<ast::NominalDef>()?;
     let node_start = derive_insertion_offset(&nominal)?;
-    ctx.add_action(AssistId("add_derive"), "add `#[derive]`", |edit| {
+    ctx.add_assist(AssistId("add_derive"), "add `#[derive]`", |edit| {
         let derive_attr = nominal
             .attrs()
             .filter_map(|x| x.as_simple_call())
@@ -44,9 +44,7 @@ pub(crate) fn add_derive(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist>
         };
         edit.target(nominal.syntax().text_range());
         edit.set_cursor(offset)
-    });
-
-    ctx.build()
+    })
 }
 
 // Insert `derive` after doc comments.
diff --git a/crates/ra_assists/src/assists/add_explicit_type.rs b/crates/ra_assists/src/assists/add_explicit_type.rs
index ffbdc0b62..ddda1a0f2 100644
--- a/crates/ra_assists/src/assists/add_explicit_type.rs
+++ b/crates/ra_assists/src/assists/add_explicit_type.rs
@@ -21,7 +21,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     let x: i32 = 92;
 // }
 // ```
-pub(crate) fn add_explicit_type(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn add_explicit_type(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let stmt = ctx.find_node_at_offset::<LetStmt>()?;
     let expr = stmt.initializer()?;
     let pat = stmt.pat()?;
@@ -47,11 +47,10 @@ pub(crate) fn add_explicit_type(mut ctx: AssistCtx<impl HirDatabase>) -> Option<
         return None;
     }
 
-    ctx.add_action(AssistId("add_explicit_type"), "add explicit type", |edit| {
+    ctx.add_assist(AssistId("add_explicit_type"), "add explicit type", |edit| {
         edit.target(pat_range);
         edit.insert(name_range.end(), format!(": {}", ty.display(db)));
-    });
-    ctx.build()
+    })
 }
 
 /// Returns true if any type parameter is unknown
diff --git a/crates/ra_assists/src/assists/add_impl.rs b/crates/ra_assists/src/assists/add_impl.rs
index fd3588d24..7da0cfd0d 100644
--- a/crates/ra_assists/src/assists/add_impl.rs
+++ b/crates/ra_assists/src/assists/add_impl.rs
@@ -27,10 +27,10 @@ use crate::{Assist, AssistCtx, AssistId};
 //
 // }
 // ```
-pub(crate) fn add_impl(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn add_impl(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let nominal = ctx.find_node_at_offset::<ast::NominalDef>()?;
     let name = nominal.name()?;
-    ctx.add_action(AssistId("add_impl"), "add impl", |edit| {
+    ctx.add_assist(AssistId("add_impl"), "add impl", |edit| {
         edit.target(nominal.syntax().text_range());
         let type_params = nominal.type_param_list();
         let start_offset = nominal.syntax().text_range().end();
@@ -54,9 +54,7 @@ pub(crate) fn add_impl(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
         edit.set_cursor(start_offset + TextUnit::of_str(&buf));
         buf.push_str("\n}");
         edit.insert(start_offset, buf);
-    });
-
-    ctx.build()
+    })
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/assists/add_import.rs b/crates/ra_assists/src/assists/add_import.rs
index 149d1403f..e87fae1af 100644
--- a/crates/ra_assists/src/assists/add_import.rs
+++ b/crates/ra_assists/src/assists/add_import.rs
@@ -1,5 +1,3 @@
-//! FIXME: write short doc here
-
 use hir::{self, db::HirDatabase};
 use ra_syntax::{
     ast::{self, NameOwner},
@@ -14,9 +12,9 @@ use crate::{
     AssistId,
 };
 
-// This function produces sequence of text edits into edit
-// to import the target path in the most appropriate scope given
-// the cursor position
+/// This function produces sequence of text edits into edit
+/// to import the target path in the most appropriate scope given
+/// the cursor position
 pub fn auto_import_text_edit(
     // Ideally the position of the cursor, used to
     position: &SyntaxNode,
@@ -39,7 +37,20 @@ pub fn auto_import_text_edit(
     }
 }
 
-pub(crate) fn add_import(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+// Assist: add_import
+//
+// Adds a use statement for a given fully-qualified path.
+//
+// ```
+// fn process(map: std::collections::<|>HashMap<String, String>) {}
+// ```
+// ->
+// ```
+// use std::collections::HashMap;
+//
+// fn process(map: HashMap<String, String>) {}
+// ```
+pub(crate) fn add_import(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let path: ast::Path = ctx.find_node_at_offset()?;
     // We don't want to mess with use statements
     if path.syntax().ancestors().find_map(ast::UseItem::cast).is_some() {
@@ -52,38 +63,18 @@ pub(crate) fn add_import(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist>
         return None;
     }
 
-    if let Some(module) = path.syntax().ancestors().find_map(ast::Module::cast) {
-        if let (Some(item_list), Some(name)) = (module.item_list(), module.name()) {
-            ctx.add_action(
-                AssistId("add_import"),
-                format!("import {} in mod {}", fmt_segments(&segments), name.text()),
-                |edit| {
-                    apply_auto_import(
-                        item_list.syntax(),
-                        &path,
-                        &segments,
-                        edit.text_edit_builder(),
-                    );
-                },
-            );
+    let module = path.syntax().ancestors().find_map(ast::Module::cast);
+    let position = match module.and_then(|it| it.item_list()) {
+        Some(item_list) => item_list.syntax().clone(),
+        None => {
+            let current_file = path.syntax().ancestors().find_map(ast::SourceFile::cast)?;
+            current_file.syntax().clone()
         }
-    } else {
-        let current_file = path.syntax().ancestors().find_map(ast::SourceFile::cast)?;
-        ctx.add_action(
-            AssistId("add_import"),
-            format!("import {} in the current file", fmt_segments(&segments)),
-            |edit| {
-                apply_auto_import(
-                    current_file.syntax(),
-                    &path,
-                    &segments,
-                    edit.text_edit_builder(),
-                );
-            },
-        );
-    }
+    };
 
-    ctx.build()
+    ctx.add_assist(AssistId("add_import"), format!("import {}", fmt_segments(&segments)), |edit| {
+        apply_auto_import(&position, &path, &segments, edit.text_edit_builder());
+    })
 }
 
 fn collect_path_segments_raw(
@@ -595,9 +586,10 @@ fn collect_hir_path_segments(path: &hir::Path) -> Option<Vec<SmolStr>> {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use crate::helpers::{check_assist, check_assist_not_applicable};
 
+    use super::*;
+
     #[test]
     fn test_auto_import_add_use_no_anchor() {
         check_assist(
diff --git a/crates/ra_assists/src/assists/add_missing_impl_members.rs b/crates/ra_assists/src/assists/add_missing_impl_members.rs
index 2585f3045..41de23921 100644
--- a/crates/ra_assists/src/assists/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/assists/add_missing_impl_members.rs
@@ -91,7 +91,7 @@ pub(crate) fn add_missing_default_members(ctx: AssistCtx<impl HirDatabase>) -> O
 }
 
 fn add_missing_impl_members_inner(
-    mut ctx: AssistCtx<impl HirDatabase>,
+    ctx: AssistCtx<impl HirDatabase>,
     mode: AddMissingImplMembersMode,
     assist_id: &'static str,
     label: &'static str,
@@ -133,7 +133,7 @@ fn add_missing_impl_members_inner(
         return None;
     }
 
-    ctx.add_action(AssistId(assist_id), label, |edit| {
+    ctx.add_assist(AssistId(assist_id), label, |edit| {
         let n_existing_items = impl_item_list.impl_items().count();
         let items = missing_items
             .into_iter()
@@ -150,9 +150,7 @@ fn add_missing_impl_members_inner(
 
         edit.replace_ast(impl_item_list, new_impl_item_list);
         edit.set_cursor(cursor_position);
-    });
-
-    ctx.build()
+    })
 }
 
 fn add_body(fn_def: ast::FnDef) -> ast::FnDef {
diff --git a/crates/ra_assists/src/assists/apply_demorgan.rs b/crates/ra_assists/src/assists/apply_demorgan.rs
index 8d5984a58..068da1774 100644
--- a/crates/ra_assists/src/assists/apply_demorgan.rs
+++ b/crates/ra_assists/src/assists/apply_demorgan.rs
@@ -23,7 +23,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     if !(x == 4 && y) {}
 // }
 // ```
-pub(crate) fn apply_demorgan(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn apply_demorgan(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let expr = ctx.find_node_at_offset::<ast::BinExpr>()?;
     let op = expr.op_kind()?;
     let op_range = expr.op_token()?.text_range();
@@ -39,13 +39,12 @@ pub(crate) fn apply_demorgan(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Ass
     let not_lhs = undo_negation(lhs)?;
     let not_rhs = undo_negation(rhs)?;
 
-    ctx.add_action(AssistId("apply_demorgan"), "apply demorgan's law", |edit| {
+    ctx.add_assist(AssistId("apply_demorgan"), "apply demorgan's law", |edit| {
         edit.target(op_range);
         edit.replace(op_range, opposite_op);
         edit.replace(lhs_range, format!("!({}", not_lhs));
         edit.replace(rhs_range, format!("{})", not_rhs));
-    });
-    ctx.build()
+    })
 }
 
 // Return the opposite text for a given logical operator, if it makes sense
diff --git a/crates/ra_assists/src/assists/change_visibility.rs b/crates/ra_assists/src/assists/change_visibility.rs
index 770ea04fa..132c9dc1d 100644
--- a/crates/ra_assists/src/assists/change_visibility.rs
+++ b/crates/ra_assists/src/assists/change_visibility.rs
@@ -29,7 +29,7 @@ pub(crate) fn change_visibility(ctx: AssistCtx<impl HirDatabase>) -> Option<Assi
     add_vis(ctx)
 }
 
-fn add_vis(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+fn add_vis(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let item_keyword = ctx.token_at_offset().find(|leaf| match leaf.kind() {
         T![fn] | T![mod] | T![struct] | T![enum] | T![trait] => true,
         _ => false,
@@ -57,13 +57,11 @@ fn add_vis(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
         (vis_offset(field.syntax()), ident.text_range())
     };
 
-    ctx.add_action(AssistId("change_visibility"), "make pub(crate)", |edit| {
+    ctx.add_assist(AssistId("change_visibility"), "make pub(crate)", |edit| {
         edit.target(target);
         edit.insert(offset, "pub(crate) ");
         edit.set_cursor(offset);
-    });
-
-    ctx.build()
+    })
 }
 
 fn vis_offset(node: &SyntaxNode) -> TextUnit {
@@ -77,24 +75,20 @@ fn vis_offset(node: &SyntaxNode) -> TextUnit {
         .unwrap_or_else(|| node.text_range().start())
 }
 
-fn change_vis(mut ctx: AssistCtx<impl HirDatabase>, vis: ast::Visibility) -> Option<Assist> {
+fn change_vis(ctx: AssistCtx<impl HirDatabase>, vis: ast::Visibility) -> Option<Assist> {
     if vis.syntax().text() == "pub" {
-        ctx.add_action(AssistId("change_visibility"), "change to pub(crate)", |edit| {
+        return ctx.add_assist(AssistId("change_visibility"), "change to pub(crate)", |edit| {
             edit.target(vis.syntax().text_range());
             edit.replace(vis.syntax().text_range(), "pub(crate)");
             edit.set_cursor(vis.syntax().text_range().start())
         });
-
-        return ctx.build();
     }
     if vis.syntax().text() == "pub(crate)" {
-        ctx.add_action(AssistId("change_visibility"), "change to pub", |edit| {
+        return ctx.add_assist(AssistId("change_visibility"), "change to pub", |edit| {
             edit.target(vis.syntax().text_range());
             edit.replace(vis.syntax().text_range(), "pub");
             edit.set_cursor(vis.syntax().text_range().start());
         });
-
-        return ctx.build();
     }
     None
 }
diff --git a/crates/ra_assists/src/assists/early_return.rs b/crates/ra_assists/src/assists/early_return.rs
index 75822dc65..e839d831e 100644
--- a/crates/ra_assists/src/assists/early_return.rs
+++ b/crates/ra_assists/src/assists/early_return.rs
@@ -35,7 +35,7 @@ use crate::{
 //     bar();
 // }
 // ```
-pub(crate) fn convert_to_guarded_return(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn convert_to_guarded_return(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let if_expr: ast::IfExpr = ctx.find_node_at_offset()?;
     let expr = if_expr.condition()?.expr()?;
     let then_block = if_expr.then_branch()?.block()?;
@@ -75,7 +75,7 @@ pub(crate) fn convert_to_guarded_return(mut ctx: AssistCtx<impl HirDatabase>) ->
     then_block.syntax().last_child_or_token().filter(|t| t.kind() == R_CURLY)?;
     let cursor_position = ctx.frange.range.start();
 
-    ctx.add_action(AssistId("convert_to_guarded_return"), "convert to guarded return", |edit| {
+    ctx.add_assist(AssistId("convert_to_guarded_return"), "convert to guarded return", |edit| {
         let if_indent_level = IndentLevel::from_node(&if_expr.syntax());
         let new_if_expr =
             if_indent_level.increase_indent(make::if_expression(&expr, early_expression));
@@ -105,8 +105,7 @@ pub(crate) fn convert_to_guarded_return(mut ctx: AssistCtx<impl HirDatabase>) ->
         edit.target(if_expr.syntax().text_range());
         edit.replace_ast(parent_block, ast::Block::cast(new_block).unwrap());
         edit.set_cursor(cursor_position);
-    });
-    ctx.build()
+    })
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/assists/fill_match_arms.rs b/crates/ra_assists/src/assists/fill_match_arms.rs
index c62c0efbe..2b74f355c 100644
--- a/crates/ra_assists/src/assists/fill_match_arms.rs
+++ b/crates/ra_assists/src/assists/fill_match_arms.rs
@@ -31,7 +31,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     }
 // }
 // ```
-pub(crate) fn fill_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn fill_match_arms(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let match_expr = ctx.find_node_at_offset::<ast::MatchExpr>()?;
     let match_arm_list = match_expr.match_arm_list()?;
 
@@ -53,7 +53,7 @@ pub(crate) fn fill_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
     };
     let variant_list = enum_def.variant_list()?;
 
-    ctx.add_action(AssistId("fill_match_arms"), "fill match arms", |edit| {
+    ctx.add_assist(AssistId("fill_match_arms"), "fill match arms", |edit| {
         let indent_level = IndentLevel::from_node(match_arm_list.syntax());
 
         let new_arm_list = {
@@ -67,9 +67,7 @@ pub(crate) fn fill_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
         edit.target(match_expr.syntax().text_range());
         edit.set_cursor(expr.syntax().text_range().start());
         edit.replace_ast(match_arm_list, new_arm_list);
-    });
-
-    ctx.build()
+    })
 }
 
 fn is_trivial(arm: &ast::MatchArm) -> bool {
diff --git a/crates/ra_assists/src/assists/flip_binexpr.rs b/crates/ra_assists/src/assists/flip_binexpr.rs
index 9765d5ddd..386045eb0 100644
--- a/crates/ra_assists/src/assists/flip_binexpr.rs
+++ b/crates/ra_assists/src/assists/flip_binexpr.rs
@@ -18,7 +18,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     let _ = 2 + 90;
 // }
 // ```
-pub(crate) fn flip_binexpr(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn flip_binexpr(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let expr = ctx.find_node_at_offset::<BinExpr>()?;
     let lhs = expr.lhs()?.syntax().clone();
     let rhs = expr.rhs()?.syntax().clone();
@@ -34,16 +34,14 @@ pub(crate) fn flip_binexpr(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assis
         return None;
     }
 
-    ctx.add_action(AssistId("flip_binexpr"), "flip binary expression", |edit| {
+    ctx.add_assist(AssistId("flip_binexpr"), "flip binary expression", |edit| {
         edit.target(op_range);
         if let FlipAction::FlipAndReplaceOp(new_op) = action {
             edit.replace(op_range, new_op);
         }
         edit.replace(lhs.text_range(), rhs.text());
         edit.replace(rhs.text_range(), lhs.text());
-    });
-
-    ctx.build()
+    })
 }
 
 enum FlipAction {
diff --git a/crates/ra_assists/src/assists/flip_comma.rs b/crates/ra_assists/src/assists/flip_comma.rs
index 53ba8011d..9be1c1dc6 100644
--- a/crates/ra_assists/src/assists/flip_comma.rs
+++ b/crates/ra_assists/src/assists/flip_comma.rs
@@ -18,7 +18,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     ((3, 4), (1, 2));
 // }
 // ```
-pub(crate) fn flip_comma(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn flip_comma(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let comma = ctx.find_token_at_offset(T![,])?;
     let prev = non_trivia_sibling(comma.clone().into(), Direction::Prev)?;
     let next = non_trivia_sibling(comma.clone().into(), Direction::Next)?;
@@ -29,13 +29,11 @@ pub(crate) fn flip_comma(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist>
         return None;
     }
 
-    ctx.add_action(AssistId("flip_comma"), "flip comma", |edit| {
+    ctx.add_assist(AssistId("flip_comma"), "flip comma", |edit| {
         edit.target(comma.text_range());
         edit.replace(prev.text_range(), next.to_string());
         edit.replace(next.text_range(), prev.to_string());
-    });
-
-    ctx.build()
+    })
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/assists/flip_trait_bound.rs b/crates/ra_assists/src/assists/flip_trait_bound.rs
index 1625b241f..6017b39dd 100644
--- a/crates/ra_assists/src/assists/flip_trait_bound.rs
+++ b/crates/ra_assists/src/assists/flip_trait_bound.rs
@@ -18,7 +18,7 @@ use crate::{Assist, AssistCtx, AssistId};
 // ```
 // fn foo<T: Copy + Clone>() { }
 // ```
-pub(crate) fn flip_trait_bound(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn flip_trait_bound(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     // We want to replicate the behavior of `flip_binexpr` by only suggesting
     // the assist when the cursor is on a `+`
     let plus = ctx.find_token_at_offset(T![+])?;
@@ -33,13 +33,11 @@ pub(crate) fn flip_trait_bound(mut ctx: AssistCtx<impl HirDatabase>) -> Option<A
         non_trivia_sibling(plus.clone().into(), Direction::Next)?,
     );
 
-    ctx.add_action(AssistId("flip_trait_bound"), "flip trait bound", |edit| {
+    ctx.add_assist(AssistId("flip_trait_bound"), "flip trait bound", |edit| {
         edit.target(plus.text_range());
         edit.replace(before.text_range(), after.to_string());
         edit.replace(after.text_range(), before.to_string());
-    });
-
-    ctx.build()
+    })
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/assists/inline_local_variable.rs b/crates/ra_assists/src/assists/inline_local_variable.rs
index fe8fa2a86..f43910574 100644
--- a/crates/ra_assists/src/assists/inline_local_variable.rs
+++ b/crates/ra_assists/src/assists/inline_local_variable.rs
@@ -23,7 +23,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     (1 + 2) * 4;
 // }
 // ```
-pub(crate) fn inline_local_varialbe(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn inline_local_varialbe(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let let_stmt = ctx.find_node_at_offset::<ast::LetStmt>()?;
     let bind_pat = match let_stmt.pat()? {
         ast::Pat::BindPat(pat) => pat,
@@ -93,7 +93,7 @@ pub(crate) fn inline_local_varialbe(mut ctx: AssistCtx<impl HirDatabase>) -> Opt
     let init_str = initializer_expr.syntax().text().to_string();
     let init_in_paren = format!("({})", &init_str);
 
-    ctx.add_action(
+    ctx.add_assist(
         AssistId("inline_local_variable"),
         "inline local variable",
         move |edit: &mut AssistBuilder| {
@@ -107,9 +107,7 @@ pub(crate) fn inline_local_varialbe(mut ctx: AssistCtx<impl HirDatabase>) -> Opt
             }
             edit.set_cursor(delete_range.start())
         },
-    );
-
-    ctx.build()
+    )
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/assists/introduce_variable.rs b/crates/ra_assists/src/assists/introduce_variable.rs
index 8245dc99f..0623d4475 100644
--- a/crates/ra_assists/src/assists/introduce_variable.rs
+++ b/crates/ra_assists/src/assists/introduce_variable.rs
@@ -28,7 +28,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     var_name * 4;
 // }
 // ```
-pub(crate) fn introduce_variable(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn introduce_variable(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     if ctx.frange.range.is_empty() {
         return None;
     }
@@ -43,7 +43,7 @@ pub(crate) fn introduce_variable(mut ctx: AssistCtx<impl HirDatabase>) -> Option
     if indent.kind() != WHITESPACE {
         return None;
     }
-    ctx.add_action(AssistId("introduce_variable"), "introduce variable", move |edit| {
+    ctx.add_assist(AssistId("introduce_variable"), "introduce variable", move |edit| {
         let mut buf = String::new();
 
         let cursor_offset = if wrap_in_block {
@@ -88,9 +88,7 @@ pub(crate) fn introduce_variable(mut ctx: AssistCtx<impl HirDatabase>) -> Option
             }
         }
         edit.set_cursor(anchor_stmt.text_range().start() + cursor_offset);
-    });
-
-    ctx.build()
+    })
 }
 
 /// Check whether the node is a valid expression which can be extracted to a variable.
diff --git a/crates/ra_assists/src/assists/merge_match_arms.rs b/crates/ra_assists/src/assists/merge_match_arms.rs
index b0c4ee78b..e9f2cae91 100644
--- a/crates/ra_assists/src/assists/merge_match_arms.rs
+++ b/crates/ra_assists/src/assists/merge_match_arms.rs
@@ -26,7 +26,7 @@ use ra_syntax::ast::{AstNode, MatchArm};
 //     }
 // }
 // ```
-pub(crate) fn merge_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn merge_match_arms(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let current_arm = ctx.find_node_at_offset::<MatchArm>()?;
 
     // We check if the following match arm matches this one. We could, but don't,
@@ -52,7 +52,7 @@ pub(crate) fn merge_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<A
 
     let cursor_to_end = current_arm.syntax().text_range().end() - ctx.frange.range.start();
 
-    ctx.add_action(AssistId("merge_match_arms"), "merge match arms", |edit| {
+    ctx.add_assist(AssistId("merge_match_arms"), "merge match arms", |edit| {
         fn contains_placeholder(a: &MatchArm) -> bool {
             a.pats().any(|x| match x {
                 ra_syntax::ast::Pat::PlaceholderPat(..) => true,
@@ -80,9 +80,7 @@ pub(crate) fn merge_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<A
         edit.target(current_arm.syntax().text_range());
         edit.replace(TextRange::from_to(start, end), arm);
         edit.set_cursor(start + offset);
-    });
-
-    ctx.build()
+    })
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/assists/move_bounds.rs b/crates/ra_assists/src/assists/move_bounds.rs
index edf2897c6..3145d7625 100644
--- a/crates/ra_assists/src/assists/move_bounds.rs
+++ b/crates/ra_assists/src/assists/move_bounds.rs
@@ -22,7 +22,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     f(x)
 // }
 // ```
-pub(crate) fn move_bounds_to_where_clause(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn move_bounds_to_where_clause(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let type_param_list = ctx.find_node_at_offset::<ast::TypeParamList>()?;
 
     let mut type_params = type_param_list.type_params();
@@ -46,38 +46,30 @@ pub(crate) fn move_bounds_to_where_clause(mut ctx: AssistCtx<impl HirDatabase>)
         _ => return None,
     };
 
-    ctx.add_action(
-        AssistId("move_bounds_to_where_clause"),
-        "move_bounds_to_where_clause",
-        |edit| {
-            let new_params = type_param_list
-                .type_params()
-                .filter(|it| it.type_bound_list().is_some())
-                .map(|type_param| {
-                    let without_bounds = type_param.remove_bounds();
-                    (type_param, without_bounds)
-                });
-
-            let new_type_param_list = edit::replace_descendants(&type_param_list, new_params);
-            edit.replace_ast(type_param_list.clone(), new_type_param_list);
-
-            let where_clause = {
-                let predicates = type_param_list.type_params().filter_map(build_predicate);
-                make::where_clause(predicates)
-            };
-
-            let to_insert = match anchor.prev_sibling_or_token() {
-                Some(ref elem) if elem.kind() == WHITESPACE => {
-                    format!("{} ", where_clause.syntax())
-                }
-                _ => format!(" {}", where_clause.syntax()),
-            };
-            edit.insert(anchor.text_range().start(), to_insert);
-            edit.target(type_param_list.syntax().text_range());
-        },
-    );
-
-    ctx.build()
+    ctx.add_assist(AssistId("move_bounds_to_where_clause"), "move_bounds_to_where_clause", |edit| {
+        let new_params = type_param_list
+            .type_params()
+            .filter(|it| it.type_bound_list().is_some())
+            .map(|type_param| {
+                let without_bounds = type_param.remove_bounds();
+                (type_param, without_bounds)
+            });
+
+        let new_type_param_list = edit::replace_descendants(&type_param_list, new_params);
+        edit.replace_ast(type_param_list.clone(), new_type_param_list);
+
+        let where_clause = {
+            let predicates = type_param_list.type_params().filter_map(build_predicate);
+            make::where_clause(predicates)
+        };
+
+        let to_insert = match anchor.prev_sibling_or_token() {
+            Some(ref elem) if elem.kind() == WHITESPACE => format!("{} ", where_clause.syntax()),
+            _ => format!(" {}", where_clause.syntax()),
+        };
+        edit.insert(anchor.text_range().start(), to_insert);
+        edit.target(type_param_list.syntax().text_range());
+    })
 }
 
 fn build_predicate(param: ast::TypeParam) -> Option<ast::WherePred> {
diff --git a/crates/ra_assists/src/assists/move_guard.rs b/crates/ra_assists/src/assists/move_guard.rs
index e820a73c8..b49ec6172 100644
--- a/crates/ra_assists/src/assists/move_guard.rs
+++ b/crates/ra_assists/src/assists/move_guard.rs
@@ -32,7 +32,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     }
 // }
 // ```
-pub(crate) fn move_guard_to_arm_body(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn move_guard_to_arm_body(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let match_arm = ctx.find_node_at_offset::<MatchArm>()?;
     let guard = match_arm.guard()?;
     let space_before_guard = guard.syntax().prev_sibling_or_token();
@@ -41,7 +41,7 @@ pub(crate) fn move_guard_to_arm_body(mut ctx: AssistCtx<impl HirDatabase>) -> Op
     let arm_expr = match_arm.expr()?;
     let buf = format!("if {} {{ {} }}", guard_conditions.syntax().text(), arm_expr.syntax().text());
 
-    ctx.add_action(AssistId("move_guard_to_arm_body"), "move guard to arm body", |edit| {
+    ctx.add_assist(AssistId("move_guard_to_arm_body"), "move guard to arm body", |edit| {
         edit.target(guard.syntax().text_range());
         let offseting_amount = match space_before_guard.and_then(|it| it.into_token()) {
             Some(tok) => {
@@ -61,8 +61,7 @@ pub(crate) fn move_guard_to_arm_body(mut ctx: AssistCtx<impl HirDatabase>) -> Op
         edit.set_cursor(
             arm_expr.syntax().text_range().start() + TextUnit::from(3) - offseting_amount,
         );
-    });
-    ctx.build()
+    })
 }
 
 // Assist: move_arm_cond_to_match_guard
@@ -90,7 +89,7 @@ pub(crate) fn move_guard_to_arm_body(mut ctx: AssistCtx<impl HirDatabase>) -> Op
 //     }
 // }
 // ```
-pub(crate) fn move_arm_cond_to_match_guard(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn move_arm_cond_to_match_guard(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let match_arm: MatchArm = ctx.find_node_at_offset::<MatchArm>()?;
     let last_match_pat = match_arm.pats().last()?;
 
@@ -110,7 +109,7 @@ pub(crate) fn move_arm_cond_to_match_guard(mut ctx: AssistCtx<impl HirDatabase>)
 
     let buf = format!(" if {}", cond.syntax().text());
 
-    ctx.add_action(
+    ctx.add_assist(
         AssistId("move_arm_cond_to_match_guard"),
         "move condition to match guard",
         |edit| {
@@ -127,8 +126,7 @@ pub(crate) fn move_arm_cond_to_match_guard(mut ctx: AssistCtx<impl HirDatabase>)
             edit.insert(last_match_pat.syntax().text_range().end(), buf);
             edit.set_cursor(last_match_pat.syntax().text_range().end() + TextUnit::from(1));
         },
-    );
-    ctx.build()
+    )
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/assists/raw_string.rs b/crates/ra_assists/src/assists/raw_string.rs
index 2df48a838..6f4b66c31 100644
--- a/crates/ra_assists/src/assists/raw_string.rs
+++ b/crates/ra_assists/src/assists/raw_string.rs
@@ -22,7 +22,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     r#"Hello, World!"#;
 // }
 // ```
-pub(crate) fn make_raw_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn make_raw_string(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let token = ctx.find_token_at_offset(STRING)?;
     let text = token.text().as_str();
     let usual_string_range = find_usual_string_range(text)?;
@@ -41,7 +41,7 @@ pub(crate) fn make_raw_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
     if error.is_err() {
         return None;
     }
-    ctx.add_action(AssistId("make_raw_string"), "make raw string", |edit| {
+    ctx.add_assist(AssistId("make_raw_string"), "make raw string", |edit| {
         edit.target(token.text_range());
         let max_hash_streak = count_hashes(&unescaped);
         let mut hashes = String::with_capacity(max_hash_streak + 1);
@@ -49,8 +49,7 @@ pub(crate) fn make_raw_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
             hashes.push('#');
         }
         edit.replace(token.text_range(), format!("r{}\"{}\"{}", hashes, unescaped, hashes));
-    });
-    ctx.build()
+    })
 }
 
 // Assist: make_usual_string
@@ -68,11 +67,11 @@ pub(crate) fn make_raw_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
 //     "Hello, \"World!\"";
 // }
 // ```
-pub(crate) fn make_usual_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn make_usual_string(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let token = ctx.find_token_at_offset(RAW_STRING)?;
     let text = token.text().as_str();
     let usual_string_range = find_usual_string_range(text)?;
-    ctx.add_action(AssistId("make_usual_string"), "make usual string", |edit| {
+    ctx.add_assist(AssistId("make_usual_string"), "make usual string", |edit| {
         edit.target(token.text_range());
         // parse inside string to escape `"`
         let start_of_inside = usual_string_range.start().to_usize() + 1;
@@ -80,8 +79,7 @@ pub(crate) fn make_usual_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<
         let inside_str = &text[start_of_inside..end_of_inside];
         let escaped = inside_str.escape_default().to_string();
         edit.replace(token.text_range(), format!("\"{}\"", escaped));
-    });
-    ctx.build()
+    })
 }
 
 // Assist: add_hash
@@ -99,14 +97,13 @@ pub(crate) fn make_usual_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<
 //     r##"Hello, World!"##;
 // }
 // ```
-pub(crate) fn add_hash(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn add_hash(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let token = ctx.find_token_at_offset(RAW_STRING)?;
-    ctx.add_action(AssistId("add_hash"), "add hash to raw string", |edit| {
+    ctx.add_assist(AssistId("add_hash"), "add hash to raw string", |edit| {
         edit.target(token.text_range());
         edit.insert(token.text_range().start() + TextUnit::of_char('r'), "#");
         edit.insert(token.text_range().end(), "#");
-    });
-    ctx.build()
+    })
 }
 
 // Assist: remove_hash
@@ -124,14 +121,14 @@ pub(crate) fn add_hash(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
 //     r"Hello, World!";
 // }
 // ```
-pub(crate) fn remove_hash(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn remove_hash(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let token = ctx.find_token_at_offset(RAW_STRING)?;
     let text = token.text().as_str();
     if text.starts_with("r\"") {
         // no hash to remove
         return None;
     }
-    ctx.add_action(AssistId("remove_hash"), "remove hash from raw string", |edit| {
+    ctx.add_assist(AssistId("remove_hash"), "remove hash from raw string", |edit| {
         edit.target(token.text_range());
         let result = &text[2..text.len() - 1];
         let result = if result.starts_with("\"") {
@@ -142,8 +139,7 @@ pub(crate) fn remove_hash(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist
             result.to_owned()
         };
         edit.replace(token.text_range(), format!("r{}", result));
-    });
-    ctx.build()
+    })
 }
 
 fn count_hashes(s: &str) -> usize {
@@ -159,10 +155,17 @@ fn count_hashes(s: &str) -> usize {
 }
 
 fn find_usual_string_range(s: &str) -> Option<TextRange> {
-    Some(TextRange::from_to(
-        TextUnit::from(s.find('"')? as u32),
-        TextUnit::from(s.rfind('"')? as u32),
-    ))
+    let left_quote = s.find('"')?;
+    let right_quote = s.rfind('"')?;
+    if left_quote == right_quote {
+        // `s` only contains one quote
+        None
+    } else {
+        Some(TextRange::from_to(
+            TextUnit::from(left_quote as u32),
+            TextUnit::from(right_quote as u32),
+        ))
+    }
 }
 
 #[cfg(test)]
@@ -272,6 +275,30 @@ string"###;
     }
 
     #[test]
+    fn make_raw_string_not_works_on_partial_string() {
+        check_assist_not_applicable(
+            make_raw_string,
+            r#"
+            fn f() {
+                let s = "foo<|>
+            }
+            "#,
+        )
+    }
+
+    #[test]
+    fn make_usual_string_not_works_on_partial_string() {
+        check_assist_not_applicable(
+            make_usual_string,
+            r#"
+            fn main() {
+                let s = r#"bar<|>
+            }
+            "#,
+        )
+    }
+
+    #[test]
     fn add_hash_target() {
         check_assist_target(
             add_hash,
diff --git a/crates/ra_assists/src/assists/remove_dbg.rs b/crates/ra_assists/src/assists/remove_dbg.rs
index 44b8de814..aedf8747f 100644
--- a/crates/ra_assists/src/assists/remove_dbg.rs
+++ b/crates/ra_assists/src/assists/remove_dbg.rs
@@ -21,7 +21,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     92;
 // }
 // ```
-pub(crate) fn remove_dbg(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn remove_dbg(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let macro_call = ctx.find_node_at_offset::<ast::MacroCall>()?;
 
     if !is_valid_macrocall(&macro_call, "dbg")? {
@@ -58,13 +58,11 @@ pub(crate) fn remove_dbg(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist>
         text.slice(without_parens).to_string()
     };
 
-    ctx.add_action(AssistId("remove_dbg"), "remove dbg!()", |edit| {
+    ctx.add_assist(AssistId("remove_dbg"), "remove dbg!()", |edit| {
         edit.target(macro_call.syntax().text_range());
         edit.replace(macro_range, macro_content);
         edit.set_cursor(cursor_pos);
-    });
-
-    ctx.build()
+    })
 }
 
 /// Verifies that the given macro_call actually matches the given name
diff --git a/crates/ra_assists/src/assists/replace_if_let_with_match.rs b/crates/ra_assists/src/assists/replace_if_let_with_match.rs
index 58ef2ff20..dff84d865 100644
--- a/crates/ra_assists/src/assists/replace_if_let_with_match.rs
+++ b/crates/ra_assists/src/assists/replace_if_let_with_match.rs
@@ -31,7 +31,7 @@ use crate::{Assist, AssistCtx, AssistId};
 //     }
 // }
 // ```
-pub(crate) fn replace_if_let_with_match(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn replace_if_let_with_match(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let if_expr: ast::IfExpr = ctx.find_node_at_offset()?;
     let cond = if_expr.condition()?;
     let pat = cond.pat()?;
@@ -42,14 +42,12 @@ pub(crate) fn replace_if_let_with_match(mut ctx: AssistCtx<impl HirDatabase>) ->
         ast::ElseBranch::IfExpr(_) => return None,
     };
 
-    ctx.add_action(AssistId("replace_if_let_with_match"), "replace with match", |edit| {
+    ctx.add_assist(AssistId("replace_if_let_with_match"), "replace with match", |edit| {
         let match_expr = build_match_expr(expr, pat, then_block, else_block);
         edit.target(if_expr.syntax().text_range());
         edit.replace_node_and_indent(if_expr.syntax(), match_expr);
         edit.set_cursor(if_expr.syntax().text_range().start())
-    });
-
-    ctx.build()
+    })
 }
 
 fn build_match_expr(
diff --git a/crates/ra_assists/src/assists/split_import.rs b/crates/ra_assists/src/assists/split_import.rs
index 8d8a28987..5f8d6b0be 100644
--- a/crates/ra_assists/src/assists/split_import.rs
+++ b/crates/ra_assists/src/assists/split_import.rs
@@ -16,7 +16,7 @@ use crate::{Assist, AssistCtx, AssistId};
 // ```
 // use std::{collections::HashMap};
 // ```
-pub(crate) fn split_import(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+pub(crate) fn split_import(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let colon_colon = ctx.find_token_at_offset(T![::])?;
     let path = ast::Path::cast(colon_colon.parent())?;
     let top_path = successors(Some(path), |it| it.parent_path()).last()?;
@@ -32,14 +32,12 @@ pub(crate) fn split_import(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assis
         None => top_path.syntax().text_range().end(),
     };
 
-    ctx.add_action(AssistId("split_import"), "split import", |edit| {
+    ctx.add_assist(AssistId("split_import"), "split import", |edit| {
         edit.target(colon_colon.text_range());
         edit.insert(l_curly, "{");
         edit.insert(r_curly, "}");
         edit.set_cursor(l_curly + TextUnit::of_str("{"));
-    });
-
-    ctx.build()
+    })
 }
 
 #[cfg(test)]
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index ebe49aecf..1bee76f59 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -142,6 +142,21 @@ impl T for () {
 }
 
 #[test]
+fn doctest_add_import() {
+    check(
+        "add_import",
+        r#####"
+fn process(map: std::collections::<|>HashMap<String, String>) {}
+"#####,
+        r#####"
+use std::collections::HashMap;
+
+fn process(map: HashMap<String, String>) {}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_apply_demorgan() {
     check(
         "apply_demorgan",
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index 7a1657d87..38599d4f1 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -11,7 +11,6 @@ mod marks;
 mod doc_tests;
 
 use hir::db::HirDatabase;
-use itertools::Itertools;
 use ra_db::FileRange;
 use ra_syntax::{TextRange, TextUnit};
 use ra_text_edit::TextEdit;
@@ -51,10 +50,10 @@ where
             .iter()
             .filter_map(|f| f(ctx.clone()))
             .map(|a| match a {
-                Assist::Unresolved(labels) => labels,
-                Assist::Resolved(..) => unreachable!(),
+                Assist::Unresolved { label } => label,
+                Assist::Resolved { .. } => unreachable!(),
             })
-            .concat()
+            .collect()
     })
 }
 
@@ -73,10 +72,10 @@ where
             .iter()
             .filter_map(|f| f(ctx.clone()))
             .map(|a| match a {
-                Assist::Resolved(labels_actions) => labels_actions,
-                Assist::Unresolved(..) => unreachable!(),
+                Assist::Resolved { label, action } => (label, action),
+                Assist::Unresolved { .. } => unreachable!(),
             })
-            .concat();
+            .collect::<Vec<_>>();
         a.sort_by(|a, b| match (a.1.target, b.1.target) {
             (Some(a), Some(b)) => a.len().cmp(&b.len()),
             (Some(_), None) => Ordering::Less,
@@ -159,51 +158,17 @@ mod helpers {
         before: &str,
         after: &str,
     ) {
-        check_assist_nth_action(assist, before, after, 0)
-    }
-
-    pub(crate) fn check_assist_range(
-        assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
-        before: &str,
-        after: &str,
-    ) {
-        check_assist_range_nth_action(assist, before, after, 0)
-    }
-
-    pub(crate) fn check_assist_target(
-        assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
-        before: &str,
-        target: &str,
-    ) {
-        check_assist_target_nth_action(assist, before, target, 0)
-    }
-
-    pub(crate) fn check_assist_range_target(
-        assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
-        before: &str,
-        target: &str,
-    ) {
-        check_assist_range_target_nth_action(assist, before, target, 0)
-    }
-
-    pub(crate) fn check_assist_nth_action(
-        assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
-        before: &str,
-        after: &str,
-        index: usize,
-    ) {
         let (before_cursor_pos, before) = extract_offset(before);
         let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
         let frange =
             FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
         let assist =
             AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
-        let labels_actions = match assist {
-            Assist::Unresolved(_) => unreachable!(),
-            Assist::Resolved(labels_actions) => labels_actions,
+        let action = match assist {
+            Assist::Unresolved { .. } => unreachable!(),
+            Assist::Resolved { action, .. } => action,
         };
 
-        let (_, action) = labels_actions.get(index).expect("expect assist action at index");
         let actual = action.edit.apply(&before);
         let actual_cursor_pos = match action.cursor_position {
             None => action
@@ -216,23 +181,21 @@ mod helpers {
         assert_eq_text!(after, &actual);
     }
 
-    pub(crate) fn check_assist_range_nth_action(
+    pub(crate) fn check_assist_range(
         assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
         before: &str,
         after: &str,
-        index: usize,
     ) {
         let (range, before) = extract_range(before);
         let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
         let frange = FileRange { file_id, range };
         let assist =
             AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
-        let labels_actions = match assist {
-            Assist::Unresolved(_) => unreachable!(),
-            Assist::Resolved(labels_actions) => labels_actions,
+        let action = match assist {
+            Assist::Unresolved { .. } => unreachable!(),
+            Assist::Resolved { action, .. } => action,
         };
 
-        let (_, action) = labels_actions.get(index).expect("expect assist action at index");
         let mut actual = action.edit.apply(&before);
         if let Some(pos) = action.cursor_position {
             actual = add_cursor(&actual, pos);
@@ -240,11 +203,10 @@ mod helpers {
         assert_eq_text!(after, &actual);
     }
 
-    pub(crate) fn check_assist_target_nth_action(
+    pub(crate) fn check_assist_target(
         assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
         before: &str,
         target: &str,
-        index: usize,
     ) {
         let (before_cursor_pos, before) = extract_offset(before);
         let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
@@ -252,33 +214,30 @@ mod helpers {
             FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
         let assist =
             AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
-        let labels_actions = match assist {
-            Assist::Unresolved(_) => unreachable!(),
-            Assist::Resolved(labels_actions) => labels_actions,
+        let action = match assist {
+            Assist::Unresolved { .. } => unreachable!(),
+            Assist::Resolved { action, .. } => action,
         };
 
-        let (_, action) = labels_actions.get(index).expect("expect assist action at index");
         let range = action.target.expect("expected target on action");
         assert_eq_text!(&before[range.start().to_usize()..range.end().to_usize()], target);
     }
 
-    pub(crate) fn check_assist_range_target_nth_action(
+    pub(crate) fn check_assist_range_target(
         assist: fn(AssistCtx<MockDatabase>) -> Option<Assist>,
         before: &str,
         target: &str,
-        index: usize,
     ) {
         let (range, before) = extract_range(before);
         let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
         let frange = FileRange { file_id, range };
         let assist =
             AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
-        let labels_actions = match assist {
-            Assist::Unresolved(_) => unreachable!(),
-            Assist::Resolved(labels_actions) => labels_actions,
+        let action = match assist {
+            Assist::Unresolved { .. } => unreachable!(),
+            Assist::Resolved { action, .. } => action,
         };
 
-        let (_, action) = labels_actions.get(index).expect("expect assist action at index");
         let range = action.target.expect("expected target on action");
         assert_eq_text!(&before[range.start().to_usize()..range.end().to_usize()], target);
     }
diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index 1b2ce921a..a12da5be2 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -173,7 +173,7 @@ fn test_doc_comment_single_line_block_strips_suffix_whitespace() {
     .ok()
     .unwrap();
     let module = file.syntax().descendants().find_map(Module::cast).unwrap();
-    assert_eq!("this is mod foo", module.doc_comment_text().unwrap());
+    assert_eq!("this is mod foo ", module.doc_comment_text().unwrap());
 }
 
 #[test]
@@ -191,7 +191,27 @@ fn test_doc_comment_multi_line_block_strips_suffix() {
     .ok()
     .unwrap();
     let module = file.syntax().descendants().find_map(Module::cast).unwrap();
-    assert_eq!("        this\n        is\n        mod foo", module.doc_comment_text().unwrap());
+    assert_eq!(
+        "        this\n        is\n        mod foo\n        ",
+        module.doc_comment_text().unwrap()
+    );
+}
+
+#[test]
+fn test_comments_preserve_trailing_whitespace() {
+    let file = SourceFile::parse(
+        r#"
+/// Representation of a Realm.   
+/// In the specification these are called Realm Records.
+struct Realm {}"#,
+    )
+    .ok()
+    .unwrap();
+    let def = file.syntax().descendants().find_map(StructDef::cast).unwrap();
+    assert_eq!(
+        "Representation of a Realm.   \nIn the specification these are called Realm Records.",
+        def.doc_comment_text().unwrap()
+    );
 }
 
 #[test]
diff --git a/crates/ra_syntax/src/ast/traits.rs b/crates/ra_syntax/src/ast/traits.rs
index f275a4955..76313684e 100644
--- a/crates/ra_syntax/src/ast/traits.rs
+++ b/crates/ra_syntax/src/ast/traits.rs
@@ -120,7 +120,7 @@ pub trait DocCommentsOwner: AstNode {
                 has_comments = true;
                 let prefix_len = comment.prefix().len();
 
-                let line = comment.text().as_str();
+                let line: &str = comment.text().as_str();
 
                 // Determine if the prefix or prefix + 1 char is stripped
                 let pos =
@@ -136,7 +136,10 @@ pub trait DocCommentsOwner: AstNode {
                     line.len()
                 };
 
-                line[pos..end].trim_end().to_owned()
+                // Note that we do not trim the end of the line here
+                // since whitespace can have special meaning at the end
+                // of a line in markdown.
+                line[pos..end].to_owned()
             })
             .join("\n");
 
diff --git a/docs/user/assists.md b/docs/user/assists.md
index b1fe44d84..303353e74 100644
--- a/docs/user/assists.md
+++ b/docs/user/assists.md
@@ -136,6 +136,20 @@ impl T for () {
 }
 ```
 
+## `add_import`
+
+Adds a use statement for a given fully-qualified path.
+
+```rust
+// BEFORE
+fn process(map: std::collections::┃HashMap<String, String>) {}
+
+// AFTER
+use std::collections::HashMap;
+
+fn process(map: HashMap<String, String>) {}
+```
+
 ## `apply_demorgan`
 
 Apply [De Morgan's law](https://en.wikipedia.org/wiki/De_Morgan%27s_laws).
diff --git a/docs/user/features.md b/docs/user/features.md
index 7ae2ca7b6..c160dd70b 100644
--- a/docs/user/features.md
+++ b/docs/user/features.md
@@ -99,24 +99,10 @@ Stop `cargo watch`
 
 ### Assists (Code Actions)
 
-These are triggered in a particular context via light bulb. We use custom code on
-the VS Code side to be able to position cursor. `<|>` signifies cursor
+Assists, or code actions, are small local refactorings, available in a particular context.
+They are usually triggered by a shortcut or by clicking a light bulb icon in the editor.
 
-See [assists.md](./assists.md)
-
-- Import path
-
-```rust
-// before:
-impl std::fmt::Debug<|> for Foo {
-}
-
-// after:
-use std::fmt::Debug;
-
-impl Debug<|> for Foo {
-}
-```
+See [assists.md](./assists.md) for the list of available assists.
 
 ### Magic Completions