87 files changed, 2277 insertions, 1827 deletions
diff --git a/Cargo.lock b/Cargo.lock
index 0400c6a94..5a5edc3e2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -53,7 +53,7 @@ dependencies = [
 "backtrace-sys 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)",
 "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
 "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc-demangle 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc-demangle 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
 "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -62,7 +62,7 @@ name = "backtrace-sys"
 version = "0.1.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cc 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
 "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -130,7 +130,7 @@ dependencies = [
 [[package]]
 name = "cc"
-version = "1.0.34"
+version = "1.0.35"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
@@ -156,14 +156,14 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "clap"
-version = "2.32.0"
+version = "2.33.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
 "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "strsim 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "strsim 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "textwrap 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "unicode-width 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 "vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -264,7 +264,7 @@ version = "0.5.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -337,7 +337,7 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)",
 "synstructure 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -354,7 +354,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
 "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.52 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
@@ -562,7 +562,7 @@ name = "jemalloc-sys"
 version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "cc 1.0.34 (registry+https://github.com/rust-lang/crates.io-index)",
+ "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
 "fs_extra 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -741,7 +741,7 @@ version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -833,7 +833,7 @@ dependencies = [
 "pest 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "pest_meta 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -879,7 +879,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "quote"
-version = "0.6.11"
+version = "0.6.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -913,7 +913,7 @@ dependencies = [
 "ra_hir 0.1.0",
 "ra_project_model 0.1.0",
 "ra_syntax 0.1.0",
- "ra_vfs 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ra_vfs 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "test_utils 0.1.0",
 ]
@@ -922,7 +922,7 @@ dependencies = [
 name = "ra_cli"
 version = "0.1.0"
 dependencies = [
- "clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "failure 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 "flexi_logger 0.11.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "indicatif 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1024,7 +1024,7 @@ dependencies = [
 "ra_project_model 0.1.0",
 "ra_syntax 0.1.0",
 "ra_text_edit 0.1.0",
- "ra_vfs 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ra_vfs 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "relative-path 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde 1.0.90 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1088,7 +1088,7 @@ dependencies = [
 "parking_lot 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "ra_parser 0.1.0",
 "ra_text_edit 0.1.0",
- "rowan 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rowan 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "smol_str 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
 "test_utils 0.1.0",
 "text_unit 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1114,7 +1114,7 @@ dependencies = [
 [[package]]
 name = "ra_vfs"
-version = "0.2.1"
+version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "crossbeam-channel 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1253,7 +1253,7 @@ dependencies = [
 [[package]]
 name = "redox_syscall"
-version = "0.1.52"
+version = "0.1.54"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
@@ -1261,7 +1261,7 @@ name = "redox_termios"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "redox_syscall 0.1.52 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 [[package]]
@@ -1309,7 +1309,7 @@ dependencies = [
 [[package]]
 name = "rowan"
-version = "0.4.0"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "colosseum 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1320,7 +1320,7 @@ dependencies = [
 [[package]]
 name = "rustc-demangle"
-version = "0.1.13"
+version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
@@ -1366,7 +1366,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1411,7 +1411,7 @@ version = "1.0.90"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1480,7 +1480,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
 name = "strsim"
-version = "0.7.0"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 [[package]]
@@ -1494,7 +1494,7 @@ version = "0.15.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1504,7 +1504,7 @@ version = "0.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "proc-macro2 0.4.27 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
 "syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)",
 "unicode-xid 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
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@@ -1517,7 +1517,7 @@ dependencies = [
 "cfg-if 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
 "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
 "rand 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.52 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
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 "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
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@@ -1559,7 +1559,7 @@ version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.52 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
 "redox_termios 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
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@@ -1591,7 +1591,7 @@ dependencies = [
 [[package]]
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-version = "0.10.0"
+version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
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@@ -1627,7 +1627,7 @@ version = "0.1.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "libc 0.2.51 (registry+https://github.com/rust-lang/crates.io-index)",
- "redox_syscall 0.1.52 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.54 (registry+https://github.com/rust-lang/crates.io-index)",
 "winapi 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
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@@ -1635,7 +1635,7 @@ dependencies = [
 name = "tools"
 version = "0.1.0"
 dependencies = [
- "clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
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 "teraron 0.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1865,11 +1865,11 @@ dependencies = [
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 "checksum cargo_metadata 0.7.4 (registry+https://github.com/rust-lang/crates.io-index)" = "178d62b240c34223f265a4c1e275e37d62da163d421fc8d7f7e3ee340f803c57"
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-"checksum clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b957d88f4b6a63b9d70d5f454ac8011819c6efa7727858f458ab71c756ce2d3e"
+"checksum clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5067f5bb2d80ef5d68b4c87db81601f0b75bca627bc2ef76b141d7b846a3c6d9"
 "checksum clicolors-control 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "73abfd4c73d003a674ce5d2933fca6ce6c42480ea84a5ffe0a2dc39ed56300f9"
 "checksum cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "ddfc5b9aa5d4507acaf872de71051dfd0e309860e88966e1051e462a077aac4f"
 "checksum colosseum 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "370c83b49aedf022ee27942e8ae1d9de1cf40dc9653ee6550e4455d08f6406f9"
@@ -1953,8 +1953,8 @@ dependencies = [
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-"checksum quote 0.6.11 (registry+https://github.com/rust-lang/crates.io-index)" = "cdd8e04bd9c52e0342b406469d494fcb033be4bdbe5c606016defbb1681411e1"
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-"checksum ra_vfs 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "d75d08da053ec832676686c72dfe509fdd1e807191a50ac79087466ffefccb1c"
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@@ -1968,15 +1968,15 @@ dependencies = [
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+"checksum rustc-demangle 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)" = "ccc78bfd5acd7bf3e89cffcf899e5cb1a52d6fafa8dec2739ad70c9577a57288"
 "checksum rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7540fc8b0c49f096ee9c961cda096467dce8084bec6bdca2fc83895fd9b28cb8"
 "checksum rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "138e3e0acb6c9fb258b19b67cb8abd63c00679d2851805ea151465464fe9030a"
 "checksum ryu 0.2.7 (registry+https://github.com/rust-lang/crates.io-index)" = "eb9e9b8cde282a9fe6a42dd4681319bfb63f121b8a8ee9439c6f4107e58a46f7"
@@ -1996,7 +1996,7 @@ dependencies = [
 "checksum smallvec 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)" = "c4488ae950c49d403731982257768f48fada354a5203fe81f9bb6f43ca9002be"
 "checksum smol_str 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "d077b3367211e9c6e2e012fb804c444e0d80ab5a51ae4137739b58e6446dcaef"
 "checksum stable_deref_trait 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "dba1a27d3efae4351c8051072d619e3ade2820635c3958d826bfea39d59b54c8"
-"checksum strsim 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bb4f380125926a99e52bc279241539c018323fab05ad6368b56f93d9369ff550"
+"checksum strsim 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
 "checksum superslice 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ab16ced94dbd8a46c82fd81e3ed9a8727dac2977ea869d217bcc4ea1f122e81f"
 "checksum syn 0.15.30 (registry+https://github.com/rust-lang/crates.io-index)" = "66c8865bf5a7cbb662d8b011950060b3c8743dca141b054bf7195b20d314d8e2"
 "checksum synstructure 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)" = "73687139bf99285483c96ac0add482c3776528beac1d97d444f6e91f203a2015"
@@ -2006,7 +2006,7 @@ dependencies = [
 "checksum termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "689a3bdfaab439fd92bc87df5c4c78417d3cbe537487274e9b0b2dce76e92096"
 "checksum termios 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "72b620c5ea021d75a735c943269bb07d30c9b77d6ac6b236bc8b5c496ef05625"
 "checksum text_unit 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "158bb1c22b638b1da3c95a8ad9f061ea40d4d39fd0301be3a520f92efeeb189e"
-"checksum textwrap 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "307686869c93e71f94da64286f9a9524c0f308a9e1c87a583de8e9c9039ad3f6"
+"checksum textwrap 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
 "checksum thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c6b53e329000edc2b34dbe8545fd20e55a333362d0a321909685a19bd28c3f1b"
 "checksum threadpool 1.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "e2f0c90a5f3459330ac8bc0d2f879c693bb7a2f59689c1083fc4ef83834da865"
 "checksum time 0.1.42 (registry+https://github.com/rust-lang/crates.io-index)" = "db8dcfca086c1143c9270ac42a2bbd8a7ee477b78ac8e45b19abfb0cbede4b6f"
diff --git a/crates/ra_assists/src/add_explicit_type.rs b/crates/ra_assists/src/add_explicit_type.rs
new file mode 100644
index 000000000..cb0ac9885
--- /dev/null
+++ b/crates/ra_assists/src/add_explicit_type.rs
@@ -0,0 +1,89 @@
+use hir::{
+    HirDisplay, Ty,
+    db::HirDatabase,
+};
+use ra_syntax::{
+    SyntaxKind,
+    ast::{LetStmt, PatKind, NameOwner, AstNode}
+};
+use crate::{AssistCtx, Assist, AssistId};
+/// Add explicit type assist.
+pub(crate) fn add_explicit_type(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+    let stmt = ctx.node_at_offset::<LetStmt>()?;
+    let expr = stmt.initializer()?;
+    let pat = stmt.pat()?;
+    // Must be a binding
+    let pat = match pat.kind() {
+        PatKind::BindPat(bind_pat) => bind_pat,
+        _ => return None,
+    };
+    let pat_range = pat.syntax().range();
+    // The binding must have a name
+    let name = pat.name()?;
+    let name_range = name.syntax().range();
+    // Assist not applicable if the type has already been specified
+    if stmt.syntax().children_with_tokens().any(|child| child.kind() == SyntaxKind::COLON) {
+        return None;
+    }
+    // Infer type
+    let db = ctx.db;
+    let analyzer = hir::SourceAnalyzer::new(db, ctx.frange.file_id, stmt.syntax(), None);
+    let ty = analyzer.type_of(db, expr)?;
+    // Assist not applicable if the type is unknown
+    if is_unknown(&ty) {
+        return None;
+    }
+    ctx.add_action(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
+fn is_unknown(ty: &Ty) -> bool {
+    match ty {
+        Ty::Unknown => true,
+        Ty::Apply(a_ty) => a_ty.parameters.iter().any(is_unknown),
+        _ => false,
+    }
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::helpers::{ check_assist, check_assist_target, check_assist_not_applicable };
+    #[test]
+    fn add_explicit_type_target() {
+        check_assist_target(add_explicit_type, "fn f() { let a<|> = 1; }", "a");
+    }
+    #[test]
+    fn add_explicit_type_works_for_simple_expr() {
+        check_assist(
+            add_explicit_type,
+            "fn f() { let a<|> = 1; }",
+            "fn f() { let a<|>: i32 = 1; }",
+        );
+    }
+    #[test]
+    fn add_explicit_type_not_applicable_if_ty_not_inferred() {
+        check_assist_not_applicable(add_explicit_type, "fn f() { let a<|> = None; }");
+    }
+    #[test]
+    fn add_explicit_type_not_applicable_if_ty_already_specified() {
+        check_assist_not_applicable(add_explicit_type, "fn f() { let a<|>: i32 = 1; }");
+    }
+    #[test]
+    fn add_explicit_type_not_applicable_if_specified_ty_is_tuple() {
+        check_assist_not_applicable(add_explicit_type, "fn f() { let a<|>: (i32, i32) = (3, 4); }");
+    }
+}
diff --git a/crates/ra_assists/src/add_missing_impl_members.rs b/crates/ra_assists/src/add_missing_impl_members.rs
index 19a2d05bc..100ebb7b6 100644
--- a/crates/ra_assists/src/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/add_missing_impl_members.rs
@@ -2,7 +2,6 @@ use std::fmt::Write;
 use crate::{Assist, AssistId, AssistCtx};
-use hir::Resolver;
 use hir::db::HirDatabase;
 use ra_syntax::{SmolStr, SyntaxKind, TextRange, TextUnit, TreeArc};
 use ra_syntax::ast::{self, AstNode, AstToken, FnDef, ImplItem, ImplItemKind, NameOwner};
@@ -46,9 +45,9 @@ fn add_missing_impl_members_inner(
    let trait_def = {
        let file_id = ctx.frange.file_id;
        let position = FilePosition { file_id, offset: impl_node.syntax().range().start() };
-        let resolver = hir::source_binder::resolver_for_position(ctx.db, position);
+        let analyzer = hir::SourceAnalyzer::new(ctx.db, position.file_id, impl_node.syntax(), None);
-        resolve_target_trait_def(ctx.db, &resolver, impl_node)?
+        resolve_target_trait_def(ctx.db, &analyzer, impl_node)?
    };
    let missing_fns: Vec<_> = {
@@ -122,14 +121,14 @@ fn add_missing_impl_members_inner(
 /// implemented) to a `ast::TraitDef`.
 fn resolve_target_trait_def(
    db: &impl HirDatabase,
-    resolver: &Resolver,
+    analyzer: &hir::SourceAnalyzer,
    impl_block: &ast::ImplBlock,
 ) -> Option<TreeArc<ast::TraitDef>> {
-    let ast_path = impl_block.target_trait().map(AstNode::syntax).and_then(ast::PathType::cast)?;
+    let ast_path =
-    let hir_path = ast_path.path().and_then(hir::Path::from_ast)?;
+        impl_block.target_trait().map(AstNode::syntax).and_then(ast::PathType::cast)?.path()?;
-    match resolver.resolve_path(db, &hir_path).take_types() {
+    match analyzer.resolve_path(db, &ast_path) {
-        Some(hir::Resolution::Def(hir::ModuleDef::Trait(def))) => Some(def.source(db).1),
+        Some(hir::PathResolution::Def(hir::ModuleDef::Trait(def))) => Some(def.source(db).1),
        _ => None,
    }
 }
diff --git a/crates/ra_assists/src/fill_match_arms.rs b/crates/ra_assists/src/fill_match_arms.rs
index da67ab667..45e327cd4 100644
--- a/crates/ra_assists/src/fill_match_arms.rs
+++ b/crates/ra_assists/src/fill_match_arms.rs
@@ -1,7 +1,7 @@
 use std::fmt::Write;
 use hir::{
-    AdtDef, FieldSource, source_binder,
+    AdtDef, FieldSource,
    db::HirDatabase,
 };
 use ra_syntax::ast::{self, AstNode};
@@ -20,12 +20,8 @@ pub(crate) fn fill_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
    }
    let expr = match_expr.expr()?;
-    let function =
+    let analyzer = hir::SourceAnalyzer::new(ctx.db, ctx.frange.file_id, expr.syntax(), None);
-        source_binder::function_from_child_node(ctx.db, ctx.frange.file_id, expr.syntax())?;
+    let match_expr_ty = analyzer.type_of(ctx.db, expr)?;
-    let infer_result = function.infer(ctx.db);
-    let source_map = function.body_source_map(ctx.db);
-    let node_expr = source_map.node_expr(expr)?;
-    let match_expr_ty = infer_result[node_expr].clone();
    let enum_def = match_expr_ty.autoderef(ctx.db).find_map(|ty| match ty.as_adt() {
        Some((AdtDef::Enum(e), _)) => Some(e),
        _ => None,
diff --git a/crates/ra_assists/src/fill_struct_fields.rs b/crates/ra_assists/src/fill_struct_fields.rs
index c7790dc72..663b4f669 100644
--- a/crates/ra_assists/src/fill_struct_fields.rs
+++ b/crates/ra_assists/src/fill_struct_fields.rs
@@ -1,6 +1,6 @@
 use std::fmt::Write;
-use hir::{AdtDef, db::HirDatabase, source_binder::function_from_child_node};
+use hir::{AdtDef, db::HirDatabase};
 use ra_syntax::ast::{self, AstNode};
@@ -51,15 +51,13 @@ where
    }
    fn evaluate_struct_def_fields(&mut self) -> Option<()> {
-        let function = function_from_child_node(
+        let analyzer = hir::SourceAnalyzer::new(
            self.ctx.db,
            self.ctx.frange.file_id,
            self.struct_lit.syntax(),
-        )?;
+            None,
-        let infer_result = function.infer(self.ctx.db);
+        );
-        let source_map = function.body_source_map(self.ctx.db);
+        let struct_lit_ty = analyzer.type_of(self.ctx.db, self.struct_lit.into())?;
-        let node_expr = source_map.node_expr(self.struct_lit.into())?;
-        let struct_lit_ty = infer_result[node_expr].clone();
        let struct_def = match struct_lit_ty.as_adt() {
            Some((AdtDef::Struct(s), _)) => s,
            _ => return None,
diff --git a/crates/ra_assists/src/inline_local_variable.rs b/crates/ra_assists/src/inline_local_variable.rs
index 950c2910b..e0479ef13 100644
--- a/crates/ra_assists/src/inline_local_variable.rs
+++ b/crates/ra_assists/src/inline_local_variable.rs
@@ -1,7 +1,4 @@
-use hir::{
+use hir::db::HirDatabase;
-    db::HirDatabase,
-    source_binder::function_from_child_node,
-};
 use ra_syntax::{
    ast::{self, AstNode, AstToken, PatKind, ExprKind},
    TextRange,
@@ -29,10 +26,8 @@ pub(crate) fn inline_local_varialbe(mut ctx: AssistCtx<impl HirDatabase>) -> Opt
    } else {
        let_stmt.syntax().range()
    };
+    let analyzer = hir::SourceAnalyzer::new(ctx.db, ctx.frange.file_id, bind_pat.syntax(), None);
-    let function = function_from_child_node(ctx.db, ctx.frange.file_id, bind_pat.syntax())?;
+    let refs = analyzer.find_all_refs(bind_pat);
-    let scope = function.scopes(ctx.db);
-    let refs = scope.find_all_refs(bind_pat);
    let mut wrap_in_parens = vec![true; refs.len()];
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index c1514f8e5..ded401b63 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -86,6 +86,7 @@ where
 }
 mod add_derive;
+mod add_explicit_type;
 mod add_impl;
 mod flip_comma;
 mod flip_binexpr;
@@ -103,6 +104,7 @@ mod add_missing_impl_members;
 fn all_assists<DB: HirDatabase>() -> &'static [fn(AssistCtx<DB>) -> Option<Assist>] {
    &[
        add_derive::add_derive,
+        add_explicit_type::add_explicit_type,
        add_impl::add_impl,
        change_visibility::change_visibility,
        fill_match_arms::fill_match_arms,
diff --git a/crates/ra_assists/src/split_import.rs b/crates/ra_assists/src/split_import.rs
index 4bf1852db..57e0efaf2 100644
--- a/crates/ra_assists/src/split_import.rs
+++ b/crates/ra_assists/src/split_import.rs
@@ -1,8 +1,9 @@
+use std::iter::successors;
 use hir::db::HirDatabase;
 use ra_syntax::{
    TextUnit, AstNode, SyntaxKind::COLONCOLON,
    ast,
-    algo::generate,
 };
 use crate::{AssistCtx, Assist, AssistId};
@@ -10,7 +11,7 @@ use crate::{AssistCtx, Assist, AssistId};
 pub(crate) fn split_import(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
    let colon_colon = ctx.token_at_offset().find(|leaf| leaf.kind() == COLONCOLON)?;
    let path = ast::Path::cast(colon_colon.parent())?;
-    let top_path = generate(Some(path), |it| it.parent_path()).last()?;
+    let top_path = successors(Some(path), |it| it.parent_path()).last()?;
    let use_tree = top_path.syntax().ancestors().find_map(ast::UseTree::cast);
    if use_tree.is_none() {
diff --git a/crates/ra_batch/src/lib.rs b/crates/ra_batch/src/lib.rs
index 5bb47afb2..0cafe617d 100644
--- a/crates/ra_batch/src/lib.rs
+++ b/crates/ra_batch/src/lib.rs
@@ -9,7 +9,7 @@ use rustc_hash::FxHashMap;
 use ra_db::{
    CrateGraph, FileId, SourceRoot, SourceRootId, SourceDatabase, salsa,
 };
-use ra_hir::{db, HirInterner};
+use ra_hir::db;
 use ra_project_model::ProjectWorkspace;
 use ra_vfs::{Vfs, VfsChange};
 use vfs_filter::IncludeRustFiles;
@@ -20,7 +20,6 @@ type Result<T> = std::result::Result<T, failure::Error>;
 #[derive(Debug)]
 pub struct BatchDatabase {
    runtime: salsa::Runtime<BatchDatabase>,
-    interner: Arc<HirInterner>,
 }
 impl salsa::Database for BatchDatabase {
@@ -29,12 +28,6 @@ impl salsa::Database for BatchDatabase {
    }
 }
-impl AsRef<HirInterner> for BatchDatabase {
-    fn as_ref(&self) -> &HirInterner {
-        &self.interner
-    }
-}
 fn vfs_file_to_id(f: ra_vfs::VfsFile) -> FileId {
    FileId(f.0.into())
 }
@@ -44,8 +37,7 @@ fn vfs_root_to_id(r: ra_vfs::VfsRoot) -> SourceRootId {
 impl BatchDatabase {
    pub fn load(crate_graph: CrateGraph, vfs: &mut Vfs) -> BatchDatabase {
-        let mut db =
+        let mut db = BatchDatabase { runtime: salsa::Runtime::default() };
-            BatchDatabase { runtime: salsa::Runtime::default(), interner: Default::default() };
        db.set_crate_graph(Arc::new(crate_graph));
        // wait until Vfs has loaded all roots
diff --git a/crates/ra_db/src/lib.rs b/crates/ra_db/src/lib.rs
index f3389c91f..1cd400752 100644
--- a/crates/ra_db/src/lib.rs
+++ b/crates/ra_db/src/lib.rs
@@ -1,11 +1,8 @@
 //! ra_db defines basic database traits. The concrete DB is defined by ra_ide_api.
 mod cancellation;
 mod input;
-mod loc2id;
-use std::{
+use std::{panic, sync::Arc};
-    panic, sync::Arc,
-};
 use ra_syntax::{TextUnit, TextRange, SourceFile, TreeArc};
 use relative_path::RelativePathBuf;
@@ -16,7 +13,6 @@ pub use crate::{
    input::{
        FileId, CrateId, SourceRoot, SourceRootId, CrateGraph, Dependency, Edition,
    },
-    loc2id::LocationInterner,
 };
 pub trait CheckCanceled: panic::RefUnwindSafe {
diff --git a/crates/ra_db/src/loc2id.rs b/crates/ra_db/src/loc2id.rs
deleted file mode 100644
index eae64a4eb..000000000
--- a/crates/ra_db/src/loc2id.rs
+++ /dev/null
@@ -1,103 +0,0 @@
-use std::{panic, hash::Hash};
-use parking_lot::Mutex;
-use rustc_hash::FxHashMap;
-use ra_arena::{Arena, ArenaId};
-/// There are two principle ways to refer to things:
-///   - by their location (module in foo/bar/baz.rs at line 42)
-///   - by their numeric id (module `ModuleId(42)`)
-///
-/// The first one is more powerful (you can actually find the thing in question
-/// by id), but the second one is so much more compact.
-///
-/// `Loc2IdMap` allows us to have a cake an eat it as well: by maintaining a
-/// bidirectional mapping between positional and numeric ids, we can use compact
-/// representation which still allows us to get the actual item.
-#[derive(Debug)]
-struct Loc2IdMap<LOC, ID>
-where
-    ID: ArenaId + Clone,
-    LOC: Clone + Eq + Hash,
-{
-    id2loc: Arena<ID, LOC>,
-    loc2id: FxHashMap<LOC, ID>,
-}
-impl<LOC, ID> Default for Loc2IdMap<LOC, ID>
-where
-    ID: ArenaId + Clone,
-    LOC: Clone + Eq + Hash,
-{
-    fn default() -> Self {
-        Loc2IdMap { id2loc: Arena::default(), loc2id: FxHashMap::default() }
-    }
-}
-impl<LOC, ID> Loc2IdMap<LOC, ID>
-where
-    ID: ArenaId + Clone,
-    LOC: Clone + Eq + Hash,
-{
-    pub fn len(&self) -> usize {
-        self.id2loc.len()
-    }
-    pub fn loc2id(&mut self, loc: &LOC) -> ID {
-        match self.loc2id.get(loc) {
-            Some(id) => return id.clone(),
-            None => (),
-        }
-        let id = self.id2loc.alloc(loc.clone());
-        self.loc2id.insert(loc.clone(), id.clone());
-        id
-    }
-    pub fn id2loc(&self, id: ID) -> LOC {
-        self.id2loc[id].clone()
-    }
-}
-#[derive(Debug)]
-pub struct LocationInterner<LOC, ID>
-where
-    ID: ArenaId + Clone,
-    LOC: Clone + Eq + Hash,
-{
-    map: Mutex<Loc2IdMap<LOC, ID>>,
-}
-impl<LOC, ID> panic::RefUnwindSafe for LocationInterner<LOC, ID>
-where
-    ID: ArenaId + Clone,
-    LOC: Clone + Eq + Hash,
-    ID: panic::RefUnwindSafe,
-    LOC: panic::RefUnwindSafe,
-{
-}
-impl<LOC, ID> Default for LocationInterner<LOC, ID>
-where
-    ID: ArenaId + Clone,
-    LOC: Clone + Eq + Hash,
-{
-    fn default() -> Self {
-        LocationInterner { map: Default::default() }
-    }
-}
-impl<LOC, ID> LocationInterner<LOC, ID>
-where
-    ID: ArenaId + Clone,
-    LOC: Clone + Eq + Hash,
-{
-    pub fn len(&self) -> usize {
-        self.map.lock().len()
-    }
-    pub fn loc2id(&self, loc: &LOC) -> ID {
-        self.map.lock().loc2id(loc)
-    }
-    pub fn id2loc(&self, id: ID) -> LOC {
-        self.map.lock().id2loc(id)
-    }
-}
diff --git a/crates/ra_fmt/src/lib.rs b/crates/ra_fmt/src/lib.rs
index 85b7ce250..603be1854 100644
--- a/crates/ra_fmt/src/lib.rs
+++ b/crates/ra_fmt/src/lib.rs
@@ -1,10 +1,10 @@
 //! This crate provides some utilities for indenting rust code.
 //!
+use std::iter::successors;
 use itertools::Itertools;
 use ra_syntax::{
    SyntaxNode, SyntaxKind::*, SyntaxToken, SyntaxKind,
    ast::{self, AstNode, AstToken},
-    algo::generate,
 };
 pub fn reindent(text: &str, indent: &str) -> String {
@@ -29,7 +29,7 @@ pub fn leading_indent(node: &SyntaxNode) -> Option<&str> {
 }
 fn prev_tokens(token: SyntaxToken) -> impl Iterator<Item = SyntaxToken> {
-    generate(token.prev_token(), |&token| token.prev_token())
+    successors(token.prev_token(), |&token| token.prev_token())
 }
 pub fn extract_trivial_expression(block: &ast::Block) -> Option<&ast::Expr> {
diff --git a/crates/ra_hir/src/code_model_api.rs b/crates/ra_hir/src/code_model_api.rs
index 9e6170440..8f1ed1086 100644
--- a/crates/ra_hir/src/code_model_api.rs
+++ b/crates/ra_hir/src/code_model_api.rs
@@ -4,14 +4,14 @@ use ra_db::{CrateId, SourceRootId, Edition};
 use ra_syntax::{ast::self, TreeArc};
 use crate::{
-    Name, ScopesWithSourceMap, Ty, HirFileId, ImportSource,
+    Name, Ty, HirFileId, Either,
    HirDatabase, DefDatabase,
    type_ref::TypeRef,
    nameres::{ModuleScope, Namespace, ImportId, CrateModuleId},
    expr::{Body, BodySourceMap},
    ty::InferenceResult,
    adt::{EnumVariantId, StructFieldId, VariantDef},
-    generics::GenericParams,
+    generics::HasGenericParams,
    docs::{Documentation, Docs, docs_from_ast},
    ids::{FunctionId, StructId, EnumId, AstItemDef, ConstId, StaticId, TraitId, TypeAliasId},
    impl_block::ImplBlock,
@@ -117,8 +117,14 @@ impl Module {
    }
    /// Returns the syntax of the last path segment corresponding to this import
-    pub fn import_source(&self, db: &impl HirDatabase, import: ImportId) -> ImportSource {
+    pub fn import_source(
-        self.import_source_impl(db, import)
+        &self,
+        db: &impl HirDatabase,
+        import: ImportId,
+    ) -> Either<TreeArc<ast::UseTree>, TreeArc<ast::ExternCrateItem>> {
+        let (file_id, source) = self.definition_source(db);
+        let (_, source_map) = db.raw_items_with_source_map(file_id);
+        source_map.get(&source, import)
    }
    /// Returns the crate this module is part of.
@@ -183,12 +189,12 @@ impl Module {
        }
    }
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl DefDatabase) -> Resolver {
        let def_map = db.crate_def_map(self.krate);
        Resolver::default().push_module_scope(def_map, self.module_id)
    }
-    pub fn declarations(self, db: &impl HirDatabase) -> Vec<ModuleDef> {
+    pub fn declarations(self, db: &impl DefDatabase) -> Vec<ModuleDef> {
        let def_map = db.crate_def_map(self.krate);
        def_map[self.module_id]
            .scope
@@ -293,10 +299,6 @@ impl Struct {
            .map(|(id, _)| StructField { parent: (*self).into(), id })
    }
-    pub fn generic_params(&self, db: &impl DefDatabase) -> Arc<GenericParams> {
-        db.generic_params((*self).into())
-    }
    pub fn ty(&self, db: &impl HirDatabase) -> Ty {
        db.type_for_def((*self).into(), Namespace::Types)
    }
@@ -307,7 +309,7 @@ impl Struct {
    // FIXME move to a more general type
    /// Builds a resolver for type references inside this struct.
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        // take the outer scope...
        let r = self.module(db).resolver(db);
        // ...and add generic params, if present
@@ -357,17 +359,13 @@ impl Enum {
            .map(|(id, _)| EnumVariant { parent: *self, id })
    }
-    pub fn generic_params(&self, db: &impl DefDatabase) -> Arc<GenericParams> {
-        db.generic_params((*self).into())
-    }
    pub fn ty(&self, db: &impl HirDatabase) -> Ty {
        db.type_for_def((*self).into(), Namespace::Types)
    }
    // FIXME: move to a more general type
    /// Builds a resolver for type references inside this struct.
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        // take the outer scope...
        let r = self.module(db).resolver(db);
        // ...and add generic params, if present
@@ -444,28 +442,22 @@ impl DefWithBody {
        db.infer(*self)
    }
-    pub fn body_source_map(&self, db: &impl HirDatabase) -> Arc<BodySourceMap> {
-        db.body_with_source_map(*self).1
-    }
    pub fn body(&self, db: &impl HirDatabase) -> Arc<Body> {
        db.body_hir(*self)
    }
+    pub fn body_source_map(&self, db: &impl HirDatabase) -> Arc<BodySourceMap> {
+        db.body_with_source_map(*self).1
+    }
    /// Builds a resolver for code inside this item.
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        match *self {
            DefWithBody::Const(ref c) => c.resolver(db),
            DefWithBody::Function(ref f) => f.resolver(db),
            DefWithBody::Static(ref s) => s.resolver(db),
        }
    }
-    pub fn scopes(&self, db: &impl HirDatabase) -> ScopesWithSourceMap {
-        let scopes = db.expr_scopes(*self);
-        let source_map = db.body_with_source_map(*self).1;
-        ScopesWithSourceMap { scopes, source_map }
-    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
@@ -517,7 +509,7 @@ impl Function {
        self.signature(db).name.clone()
    }
-    pub fn body_source_map(&self, db: &impl HirDatabase) -> Arc<BodySourceMap> {
+    pub(crate) fn body_source_map(&self, db: &impl HirDatabase) -> Arc<BodySourceMap> {
        db.body_with_source_map((*self).into()).1
    }
@@ -529,12 +521,6 @@ impl Function {
        db.type_for_def((*self).into(), Namespace::Values)
    }
-    pub fn scopes(&self, db: &impl HirDatabase) -> ScopesWithSourceMap {
-        let scopes = db.expr_scopes((*self).into());
-        let source_map = db.body_with_source_map((*self).into()).1;
-        ScopesWithSourceMap { scopes, source_map }
-    }
    pub fn signature(&self, db: &impl HirDatabase) -> Arc<FnSignature> {
        db.fn_signature(*self)
    }
@@ -543,24 +529,32 @@ impl Function {
        db.infer((*self).into())
    }
-    pub fn generic_params(&self, db: &impl DefDatabase) -> Arc<GenericParams> {
-        db.generic_params((*self).into())
-    }
    /// The containing impl block, if this is a method.
    pub fn impl_block(&self, db: &impl DefDatabase) -> Option<ImplBlock> {
        let module_impls = db.impls_in_module(self.module(db));
        ImplBlock::containing(module_impls, (*self).into())
    }
+    /// The containing trait, if this is a trait method definition.
+    pub fn parent_trait(&self, db: &impl DefDatabase) -> Option<Trait> {
+        db.trait_items_index(self.module(db)).get_parent_trait((*self).into())
+    }
+    pub fn container(&self, db: &impl DefDatabase) -> Option<Container> {
+        if let Some(impl_block) = self.impl_block(db) {
+            Some(impl_block.into())
+        } else if let Some(trait_) = self.parent_trait(db) {
+            Some(trait_.into())
+        } else {
+            None
+        }
+    }
    // FIXME: move to a more general type for 'body-having' items
    /// Builds a resolver for code inside this item.
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        // take the outer scope...
-        let r = self
+        let r = self.container(db).map_or_else(|| self.module(db).resolver(db), |c| c.resolver(db));
-            .impl_block(db)
-            .map(|ib| ib.resolver(db))
-            .unwrap_or_else(|| self.module(db).resolver(db));
        // ...and add generic params, if present
        let p = self.generic_params(db);
        let r = if !p.params.is_empty() { r.push_generic_params_scope(p) } else { r };
@@ -600,10 +594,6 @@ impl Const {
        db.infer((*self).into())
    }
-    pub fn body_source_map(&self, db: &impl HirDatabase) -> Arc<BodySourceMap> {
-        db.body_with_source_map((*self).into()).1
-    }
    /// The containing impl block, if this is a method.
    pub fn impl_block(&self, db: &impl DefDatabase) -> Option<ImplBlock> {
        let module_impls = db.impls_in_module(self.module(db));
@@ -612,7 +602,7 @@ impl Const {
    // FIXME: move to a more general type for 'body-having' items
    /// Builds a resolver for code inside this item.
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        // take the outer scope...
        let r = self
            .impl_block(db)
@@ -664,7 +654,7 @@ impl Static {
    }
    /// Builds a resolver for code inside this item.
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        // take the outer scope...
        self.module(db).resolver(db)
    }
@@ -672,10 +662,6 @@ impl Static {
    pub fn infer(&self, db: &impl HirDatabase) -> Arc<InferenceResult> {
        db.infer((*self).into())
    }
-    pub fn body_source_map(&self, db: &impl HirDatabase) -> Arc<BodySourceMap> {
-        db.body_with_source_map((*self).into()).1
-    }
 }
 impl Docs for Static {
@@ -698,10 +684,6 @@ impl Trait {
        self.id.module(db)
    }
-    pub fn generic_params(&self, db: &impl DefDatabase) -> Arc<GenericParams> {
-        db.generic_params((*self).into())
-    }
    pub fn name(self, db: &impl DefDatabase) -> Option<Name> {
        self.trait_data(db).name().clone()
    }
@@ -713,6 +695,14 @@ impl Trait {
    pub(crate) fn trait_data(self, db: &impl DefDatabase) -> Arc<TraitData> {
        db.trait_data(self)
    }
+    pub(crate) fn resolver(&self, db: &impl DefDatabase) -> Resolver {
+        let r = self.module(db).resolver(db);
+        // add generic params, if present
+        let p = self.generic_params(db);
+        let r = if !p.params.is_empty() { r.push_generic_params_scope(p) } else { r };
+        r
+    }
 }
 impl Docs for Trait {
@@ -731,10 +721,6 @@ impl TypeAlias {
        self.id.source(db)
    }
-    pub fn generic_params(&self, db: &impl DefDatabase) -> Arc<GenericParams> {
-        db.generic_params((*self).into())
-    }
    pub fn module(&self, db: &impl DefDatabase) -> Module {
        self.id.module(db)
    }
@@ -745,12 +731,27 @@ impl TypeAlias {
        ImplBlock::containing(module_impls, (*self).into())
    }
+    /// The containing trait, if this is a trait method definition.
+    pub fn parent_trait(&self, db: &impl DefDatabase) -> Option<Trait> {
+        db.trait_items_index(self.module(db)).get_parent_trait((*self).into())
+    }
+    pub fn container(&self, db: &impl DefDatabase) -> Option<Container> {
+        if let Some(impl_block) = self.impl_block(db) {
+            Some(impl_block.into())
+        } else if let Some(trait_) = self.parent_trait(db) {
+            Some(trait_.into())
+        } else {
+            None
+        }
+    }
    pub fn type_ref(self, db: &impl DefDatabase) -> Arc<TypeRef> {
        db.type_alias_ref(self)
    }
    /// Builds a resolver for the type references in this type alias.
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
+    pub(crate) fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        // take the outer scope...
        let r = self
            .impl_block(db)
@@ -768,3 +769,18 @@ impl Docs for TypeAlias {
        docs_from_ast(&*self.source(db).1)
    }
 }
+pub enum Container {
+    Trait(Trait),
+    ImplBlock(ImplBlock),
+}
+impl_froms!(Container: Trait, ImplBlock);
+impl Container {
+    pub(crate) fn resolver(&self, db: &impl DefDatabase) -> Resolver {
+        match self {
+            Container::Trait(trait_) => trait_.resolver(db),
+            Container::ImplBlock(impl_block) => impl_block.resolver(db),
+        }
+    }
+}
diff --git a/crates/ra_hir/src/code_model_impl/module.rs b/crates/ra_hir/src/code_model_impl/module.rs
index 88dee3a69..5c2ea73ce 100644
--- a/crates/ra_hir/src/code_model_impl/module.rs
+++ b/crates/ra_hir/src/code_model_impl/module.rs
@@ -3,9 +3,9 @@ use ra_syntax::{ast, TreeArc};
 use crate::{
    Module, ModuleSource, Name, AstId,
-    nameres::{CrateModuleId, ImportId},
+    nameres::CrateModuleId,
    HirDatabase, DefDatabase,
-    HirFileId, ImportSource,
+    HirFileId,
 };
 impl ModuleSource {
@@ -68,16 +68,6 @@ impl Module {
        Some((decl.file_id(), ast))
    }
-    pub(crate) fn import_source_impl(
-        &self,
-        db: &impl HirDatabase,
-        import: ImportId,
-    ) -> ImportSource {
-        let (file_id, source) = self.definition_source(db);
-        let (_, source_map) = db.raw_items_with_source_map(file_id);
-        source_map.get(&source, import)
-    }
    pub(crate) fn crate_root_impl(&self, db: &impl DefDatabase) -> Module {
        let def_map = db.crate_def_map(self.krate);
        self.with_module_id(def_map.root())
diff --git a/crates/ra_hir/src/db.rs b/crates/ra_hir/src/db.rs
index be8a8c98b..18627bbc2 100644
--- a/crates/ra_hir/src/db.rs
+++ b/crates/ra_hir/src/db.rs
@@ -1,10 +1,10 @@
 use std::sync::Arc;
-use ra_syntax::{SyntaxNode, TreeArc, SourceFile};
+use ra_syntax::{SyntaxNode, TreeArc, SourceFile, ast};
 use ra_db::{SourceDatabase, salsa};
 use crate::{
-    HirFileId, MacroDefId, AstIdMap, ErasedFileAstId, Crate, Module, HirInterner,
+    HirFileId, MacroDefId, AstIdMap, ErasedFileAstId, Crate, Module, MacroCallLoc,
    Function, FnSignature, ExprScopes, TypeAlias,
    Struct, Enum, StructField,
    Const, ConstSignature, Static,
@@ -15,11 +15,29 @@ use crate::{
    impl_block::{ModuleImplBlocks, ImplSourceMap},
    generics::{GenericParams, GenericDef},
    type_ref::TypeRef,
-    traits::TraitData, Trait, ty::TraitRef
+    traits::TraitData, Trait, ty::TraitRef,
+    ids
 };
 #[salsa::query_group(DefDatabaseStorage)]
-pub trait DefDatabase: SourceDatabase + AsRef<HirInterner> {
+pub trait DefDatabase: SourceDatabase {
+    #[salsa::interned]
+    fn intern_macro(&self, macro_call: MacroCallLoc) -> ids::MacroCallId;
+    #[salsa::interned]
+    fn intern_function(&self, loc: ids::ItemLoc<ast::FnDef>) -> ids::FunctionId;
+    #[salsa::interned]
+    fn intern_struct(&self, loc: ids::ItemLoc<ast::StructDef>) -> ids::StructId;
+    #[salsa::interned]
+    fn intern_enum(&self, loc: ids::ItemLoc<ast::EnumDef>) -> ids::EnumId;
+    #[salsa::interned]
+    fn intern_const(&self, loc: ids::ItemLoc<ast::ConstDef>) -> ids::ConstId;
+    #[salsa::interned]
+    fn intern_static(&self, loc: ids::ItemLoc<ast::StaticDef>) -> ids::StaticId;
+    #[salsa::interned]
+    fn intern_trait(&self, loc: ids::ItemLoc<ast::TraitDef>) -> ids::TraitId;
+    #[salsa::interned]
+    fn intern_type_alias(&self, loc: ids::ItemLoc<ast::TypeAliasDef>) -> ids::TypeAliasId;
    #[salsa::invoke(crate::ids::macro_def_query)]
    fn macro_def(&self, macro_id: MacroDefId) -> Option<Arc<mbe::MacroRules>>;
@@ -35,6 +53,9 @@ pub trait DefDatabase: SourceDatabase + AsRef<HirInterner> {
    #[salsa::invoke(crate::traits::TraitData::trait_data_query)]
    fn trait_data(&self, t: Trait) -> Arc<TraitData>;
+    #[salsa::invoke(crate::traits::TraitItemsIndex::trait_items_index)]
+    fn trait_items_index(&self, module: Module) -> crate::traits::TraitItemsIndex;
    #[salsa::invoke(crate::source_id::AstIdMap::ast_id_map_query)]
    fn ast_id_map(&self, file_id: HirFileId) -> Arc<AstIdMap>;
@@ -110,8 +131,8 @@ pub trait HirDatabase: DefDatabase {
    #[salsa::invoke(crate::ty::method_resolution::CrateImplBlocks::impls_in_crate_query)]
    fn impls_in_crate(&self, krate: Crate) -> Arc<CrateImplBlocks>;
-    #[salsa::invoke(crate::ty::method_resolution::implements)]
+    #[salsa::invoke(crate::ty::traits::implements)]
-    fn implements(&self, trait_ref: TraitRef) -> bool;
+    fn implements(&self, trait_ref: TraitRef) -> Option<crate::ty::traits::Solution>;
 }
 #[test]
diff --git a/crates/ra_hir/src/either.rs b/crates/ra_hir/src/either.rs
new file mode 100644
index 000000000..4073cc82e
--- /dev/null
+++ b/crates/ra_hir/src/either.rs
@@ -0,0 +1,28 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Either<A, B> {
+    A(A),
+    B(B),
+}
+impl<A, B> Either<A, B> {
+    pub fn either<R, F1, F2>(self, f1: F1, f2: F2) -> R
+    where
+        F1: FnOnce(A) -> R,
+        F2: FnOnce(B) -> R,
+    {
+        match self {
+            Either::A(a) => f1(a),
+            Either::B(b) => f2(b),
+        }
+    }
+    pub fn map<U, V, F1, F2>(self, f1: F1, f2: F2) -> Either<U, V>
+    where
+        F1: FnOnce(A) -> U,
+        F2: FnOnce(B) -> V,
+    {
+        match self {
+            Either::A(a) => Either::A(f1(a)),
+            Either::B(b) => Either::B(f2(b)),
+        }
+    }
+}
diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index 589a9b2db..817e660f9 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -10,13 +10,13 @@ use ra_syntax::{
 };
 use crate::{
-    Path, Name, HirDatabase, Resolver,DefWithBody,
+    Path, Name, HirDatabase, Resolver,DefWithBody, Either,
    name::AsName,
    type_ref::{Mutability, TypeRef},
 };
-use crate::{ path::GenericArgs, ty::primitive::{IntTy, UncertainIntTy, FloatTy, UncertainFloatTy}};
+use crate::{path::GenericArgs, ty::primitive::{IntTy, UncertainIntTy, FloatTy, UncertainFloatTy}};
-pub use self::scope::{ExprScopes, ScopesWithSourceMap, ScopeEntryWithSyntax};
+pub use self::scope::ExprScopes;
 pub(crate) mod scope;
@@ -51,11 +51,13 @@ pub struct Body {
 pub struct BodySourceMap {
    expr_map: FxHashMap<SyntaxNodePtr, ExprId>,
    expr_map_back: ArenaMap<ExprId, SyntaxNodePtr>,
-    pat_map: FxHashMap<SyntaxNodePtr, PatId>,
+    pat_map: FxHashMap<PatPtr, PatId>,
-    pat_map_back: ArenaMap<PatId, SyntaxNodePtr>,
+    pat_map_back: ArenaMap<PatId, PatPtr>,
    field_map: FxHashMap<(ExprId, usize), AstPtr<ast::NamedField>>,
 }
+type PatPtr = Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>>;
 impl Body {
    pub fn params(&self) -> &[PatId] {
        &self.params
@@ -79,19 +81,23 @@ impl Body {
 }
 // needs arbitrary_self_types to be a method... or maybe move to the def?
-pub fn resolver_for_expr(body: Arc<Body>, db: &impl HirDatabase, expr_id: ExprId) -> Resolver {
+pub(crate) fn resolver_for_expr(
+    body: Arc<Body>,
+    db: &impl HirDatabase,
+    expr_id: ExprId,
+) -> Resolver {
    let scopes = db.expr_scopes(body.owner);
    resolver_for_scope(body, db, scopes.scope_for(expr_id))
 }
-pub fn resolver_for_scope(
+pub(crate) fn resolver_for_scope(
    body: Arc<Body>,
    db: &impl HirDatabase,
    scope_id: Option<scope::ScopeId>,
 ) -> Resolver {
    let mut r = body.owner.resolver(db);
    let scopes = db.expr_scopes(body.owner);
-    let scope_chain = scopes.scope_chain_for(scope_id).collect::<Vec<_>>();
+    let scope_chain = scopes.scope_chain(scope_id).collect::<Vec<_>>();
    for scope in scope_chain.into_iter().rev() {
        r = r.push_expr_scope(Arc::clone(&scopes), scope);
    }
@@ -115,31 +121,27 @@ impl Index<PatId> for Body {
 }
 impl BodySourceMap {
-    pub fn expr_syntax(&self, expr: ExprId) -> Option<SyntaxNodePtr> {
+    pub(crate) fn expr_syntax(&self, expr: ExprId) -> Option<SyntaxNodePtr> {
        self.expr_map_back.get(expr).cloned()
    }
-    pub fn syntax_expr(&self, ptr: SyntaxNodePtr) -> Option<ExprId> {
+    pub(crate) fn syntax_expr(&self, ptr: SyntaxNodePtr) -> Option<ExprId> {
        self.expr_map.get(&ptr).cloned()
    }
-    pub fn node_expr(&self, node: &ast::Expr) -> Option<ExprId> {
+    pub(crate) fn node_expr(&self, node: &ast::Expr) -> Option<ExprId> {
        self.expr_map.get(&SyntaxNodePtr::new(node.syntax())).cloned()
    }
-    pub fn pat_syntax(&self, pat: PatId) -> Option<SyntaxNodePtr> {
+    pub(crate) fn pat_syntax(&self, pat: PatId) -> Option<PatPtr> {
        self.pat_map_back.get(pat).cloned()
    }
-    pub fn syntax_pat(&self, ptr: SyntaxNodePtr) -> Option<PatId> {
+    pub(crate) fn node_pat(&self, node: &ast::Pat) -> Option<PatId> {
-        self.pat_map.get(&ptr).cloned()
+        self.pat_map.get(&Either::A(AstPtr::new(node))).cloned()
-    }
-    pub fn node_pat(&self, node: &ast::Pat) -> Option<PatId> {
-        self.pat_map.get(&SyntaxNodePtr::new(node.syntax())).cloned()
    }
-    pub fn field_syntax(&self, expr: ExprId, field: usize) -> AstPtr<ast::NamedField> {
+    pub(crate) fn field_syntax(&self, expr: ExprId, field: usize) -> AstPtr<ast::NamedField> {
        self.field_map[&(expr, field)].clone()
    }
 }
@@ -504,10 +506,10 @@ impl ExprCollector {
        id
    }
-    fn alloc_pat(&mut self, pat: Pat, syntax_ptr: SyntaxNodePtr) -> PatId {
+    fn alloc_pat(&mut self, pat: Pat, ptr: PatPtr) -> PatId {
        let id = self.pats.alloc(pat);
-        self.source_map.pat_map.insert(syntax_ptr, id);
+        self.source_map.pat_map.insert(ptr, id);
-        self.source_map.pat_map_back.insert(id, syntax_ptr);
+        self.source_map.pat_map_back.insert(id, ptr);
        id
    }
@@ -886,8 +888,8 @@ impl ExprCollector {
            ast::PatKind::LiteralPat(_) => Pat::Missing,
            ast::PatKind::SlicePat(_) | ast::PatKind::RangePat(_) => Pat::Missing,
        };
-        let syntax_ptr = SyntaxNodePtr::new(pat.syntax());
+        let ptr = AstPtr::new(pat);
-        self.alloc_pat(pattern, syntax_ptr)
+        self.alloc_pat(pattern, Either::A(ptr))
    }
    fn collect_pat_opt(&mut self, pat: Option<&ast::Pat>) -> PatId {
@@ -911,14 +913,14 @@ impl ExprCollector {
    fn collect_fn_body(&mut self, node: &ast::FnDef) {
        if let Some(param_list) = node.param_list() {
            if let Some(self_param) = param_list.self_param() {
-                let self_param = SyntaxNodePtr::new(self_param.syntax());
+                let ptr = AstPtr::new(self_param);
                let param_pat = self.alloc_pat(
                    Pat::Bind {
                        name: Name::self_param(),
                        mode: BindingAnnotation::Unannotated,
                        subpat: None,
                    },
-                    self_param,
+                    Either::B(ptr),
                );
                self.params.push(param_pat);
            }
diff --git a/crates/ra_hir/src/expr/scope.rs b/crates/ra_hir/src/expr/scope.rs
index 48283907b..58f365128 100644
--- a/crates/ra_hir/src/expr/scope.rs
+++ b/crates/ra_hir/src/expr/scope.rs
@@ -1,17 +1,11 @@
 use std::sync::Arc;
-use rustc_hash::{FxHashMap, FxHashSet};
+use rustc_hash::FxHashMap;
-use ra_syntax::{
-    AstNode, SyntaxNode, TextUnit, TextRange, SyntaxNodePtr,
-    algo::generate,
-    ast,
-};
 use ra_arena::{Arena, RawId, impl_arena_id};
 use crate::{
-    Name, AsName,DefWithBody,
+    Name, DefWithBody,
-    expr::{PatId, ExprId, Pat, Expr, Body, Statement, BodySourceMap},
+    expr::{PatId, ExprId, Pat, Expr, Body, Statement},
    HirDatabase,
 };
@@ -23,23 +17,32 @@ impl_arena_id!(ScopeId);
 pub struct ExprScopes {
    body: Arc<Body>,
    scopes: Arena<ScopeId, ScopeData>,
-    scope_for: FxHashMap<ExprId, ScopeId>,
+    scope_by_expr: FxHashMap<ExprId, ScopeId>,
 }
 #[derive(Debug, PartialEq, Eq)]
-pub struct ScopeEntry {
+pub(crate) struct ScopeEntry {
    name: Name,
    pat: PatId,
 }
+impl ScopeEntry {
+    pub(crate) fn name(&self) -> &Name {
+        &self.name
+    }
+    pub(crate) fn pat(&self) -> PatId {
+        self.pat
+    }
+}
 #[derive(Debug, PartialEq, Eq)]
-pub struct ScopeData {
+pub(crate) struct ScopeData {
    parent: Option<ScopeId>,
    entries: Vec<ScopeEntry>,
 }
 impl ExprScopes {
-    // FIXME: This should take something more general than Function
    pub(crate) fn expr_scopes_query(db: &impl HirDatabase, def: DefWithBody) -> Arc<ExprScopes> {
        let body = db.body_hir(def);
        let res = ExprScopes::new(body);
@@ -50,7 +53,7 @@ impl ExprScopes {
        let mut scopes = ExprScopes {
            body: body.clone(),
            scopes: Arena::default(),
-            scope_for: FxHashMap::default(),
+            scope_by_expr: FxHashMap::default(),
        };
        let root = scopes.root_scope();
        scopes.add_params_bindings(root, body.params());
@@ -58,19 +61,23 @@ impl ExprScopes {
        scopes
    }
-    pub fn body(&self) -> Arc<Body> {
+    pub(crate) fn entries(&self, scope: ScopeId) -> &[ScopeEntry] {
-        self.body.clone()
-    }
-    pub fn entries(&self, scope: ScopeId) -> &[ScopeEntry] {
        &self.scopes[scope].entries
    }
-    pub fn scope_chain_for<'a>(
+    pub(crate) fn scope_chain<'a>(
        &'a self,
        scope: Option<ScopeId>,
    ) -> impl Iterator<Item = ScopeId> + 'a {
-        generate(scope, move |&scope| self.scopes[scope].parent)
+        std::iter::successors(scope, move |&scope| self.scopes[scope].parent)
+    }
+    pub(crate) fn scope_for(&self, expr: ExprId) -> Option<ScopeId> {
+        self.scope_by_expr.get(&expr).map(|&scope| scope)
+    }
+    pub(crate) fn scope_by_expr(&self) -> &FxHashMap<ExprId, ScopeId> {
+        &self.scope_by_expr
    }
    fn root_scope(&mut self) -> ScopeId {
@@ -99,130 +106,7 @@ impl ExprScopes {
    }
    fn set_scope(&mut self, node: ExprId, scope: ScopeId) {
-        self.scope_for.insert(node, scope);
+        self.scope_by_expr.insert(node, scope);
-    }
-    pub fn scope_for(&self, expr: ExprId) -> Option<ScopeId> {
-        self.scope_for.get(&expr).map(|&scope| scope)
-    }
-}
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct ScopesWithSourceMap {
-    pub source_map: Arc<BodySourceMap>,
-    pub scopes: Arc<ExprScopes>,
-}
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct ScopeEntryWithSyntax {
-    name: Name,
-    ptr: SyntaxNodePtr,
-}
-impl ScopeEntryWithSyntax {
-    pub fn name(&self) -> &Name {
-        &self.name
-    }
-    pub fn ptr(&self) -> SyntaxNodePtr {
-        self.ptr
-    }
-}
-impl ScopesWithSourceMap {
-    fn scope_chain<'a>(&'a self, node: &SyntaxNode) -> impl Iterator<Item = ScopeId> + 'a {
-        generate(self.scope_for(node), move |&scope| self.scopes.scopes[scope].parent)
-    }
-    pub fn scope_for_offset(&self, offset: TextUnit) -> Option<ScopeId> {
-        self.scopes
-            .scope_for
-            .iter()
-            .filter_map(|(id, scope)| Some((self.source_map.expr_syntax(*id)?, scope)))
-            // find containing scope
-            .min_by_key(|(ptr, _scope)| {
-                (!(ptr.range().start() <= offset && offset <= ptr.range().end()), ptr.range().len())
-            })
-            .map(|(ptr, scope)| self.adjust(ptr, *scope, offset))
-    }
-    // XXX: during completion, cursor might be outside of any particular
-    // expression. Try to figure out the correct scope...
-    // FIXME: move this to source binder?
-    fn adjust(&self, ptr: SyntaxNodePtr, original_scope: ScopeId, offset: TextUnit) -> ScopeId {
-        let r = ptr.range();
-        let child_scopes = self
-            .scopes
-            .scope_for
-            .iter()
-            .filter_map(|(id, scope)| Some((self.source_map.expr_syntax(*id)?, scope)))
-            .map(|(ptr, scope)| (ptr.range(), scope))
-            .filter(|(range, _)| range.start() <= offset && range.is_subrange(&r) && *range != r);
-        child_scopes
-            .max_by(|(r1, _), (r2, _)| {
-                if r2.is_subrange(&r1) {
-                    std::cmp::Ordering::Greater
-                } else if r1.is_subrange(&r2) {
-                    std::cmp::Ordering::Less
-                } else {
-                    r1.start().cmp(&r2.start())
-                }
-            })
-            .map(|(_ptr, scope)| *scope)
-            .unwrap_or(original_scope)
-    }
-    pub fn resolve_local_name(&self, name_ref: &ast::NameRef) -> Option<ScopeEntryWithSyntax> {
-        let mut shadowed = FxHashSet::default();
-        let name = name_ref.as_name();
-        let ret = self
-            .scope_chain(name_ref.syntax())
-            .flat_map(|scope| self.scopes.entries(scope).iter())
-            .filter(|entry| shadowed.insert(entry.name()))
-            .filter(|entry| entry.name() == &name)
-            .nth(0);
-        ret.and_then(|entry| {
-            Some(ScopeEntryWithSyntax {
-                name: entry.name().clone(),
-                ptr: self.source_map.pat_syntax(entry.pat())?,
-            })
-        })
-    }
-    pub fn find_all_refs(&self, pat: &ast::BindPat) -> Vec<ReferenceDescriptor> {
-        let fn_def = pat.syntax().ancestors().find_map(ast::FnDef::cast).unwrap();
-        let name_ptr = SyntaxNodePtr::new(pat.syntax());
-        fn_def
-            .syntax()
-            .descendants()
-            .filter_map(ast::NameRef::cast)
-            .filter(|name_ref| match self.resolve_local_name(*name_ref) {
-                None => false,
-                Some(entry) => entry.ptr() == name_ptr,
-            })
-            .map(|name_ref| ReferenceDescriptor {
-                name: name_ref.syntax().text().to_string(),
-                range: name_ref.syntax().range(),
-            })
-            .collect()
-    }
-    pub fn scope_for(&self, node: &SyntaxNode) -> Option<ScopeId> {
-        node.ancestors()
-            .map(SyntaxNodePtr::new)
-            .filter_map(|ptr| self.source_map.syntax_expr(ptr))
-            .find_map(|it| self.scopes.scope_for(it))
-    }
-}
-impl ScopeEntry {
-    pub fn name(&self) -> &Name {
-        &self.name
-    }
-    pub fn pat(&self) -> PatId {
-        self.pat
    }
 }
@@ -286,22 +170,13 @@ fn compute_expr_scopes(expr: ExprId, body: &Body, scopes: &mut ExprScopes, scope
    };
 }
-#[derive(Debug)]
-pub struct ReferenceDescriptor {
-    pub range: TextRange,
-    pub name: String,
-}
 #[cfg(test)]
 mod tests {
-    use ra_syntax::{SourceFile, algo::find_node_at_offset};
+    use ra_db::SourceDatabase;
+    use ra_syntax::{algo::find_node_at_offset, AstNode, SyntaxNodePtr, ast};
    use test_utils::{extract_offset, assert_eq_text};
-    use ra_arena::ArenaId;
-    use crate::Function;
-    use crate::expr::{ExprCollector};
-    use super::*;
+    use crate::{source_binder::SourceAnalyzer, mock::MockDatabase};
    fn do_check(code: &str, expected: &[&str]) {
        let (off, code) = extract_offset(code);
@@ -313,17 +188,20 @@ mod tests {
            buf.push_str(&code[off..]);
            buf
        };
-        let file = SourceFile::parse(&code);
+        let (db, _source_root, file_id) = MockDatabase::with_single_file(&code);
+        let file = db.parse(file_id);
        let marker: &ast::PathExpr = find_node_at_offset(file.syntax(), off).unwrap();
-        let fn_def: &ast::FnDef = find_node_at_offset(file.syntax(), off).unwrap();
+        let analyzer = SourceAnalyzer::new(&db, file_id, marker.syntax(), None);
-        let irrelevant_function = Function { id: crate::ids::FunctionId::from_raw(0.into()) };
-        let (body, source_map) = collect_fn_body_syntax(irrelevant_function, fn_def);
+        let scopes = analyzer.scopes();
-        let scopes = ExprScopes::new(Arc::new(body));
+        let expr_id =
-        let scopes =
+            analyzer.body_source_map().syntax_expr(SyntaxNodePtr::new(marker.syntax())).unwrap();
-            ScopesWithSourceMap { scopes: Arc::new(scopes), source_map: Arc::new(source_map) };
+        let scope = scopes.scope_for(expr_id);
        let actual = scopes
-            .scope_chain(marker.syntax())
+            .scope_chain(scope)
-            .flat_map(|scope| scopes.scopes.entries(scope))
+            .flat_map(|scope| scopes.entries(scope))
            .map(|it| it.name().to_string())
            .collect::<Vec<_>>()
            .join("\n");
@@ -406,28 +284,19 @@ mod tests {
        );
    }
-    fn collect_fn_body_syntax(function: Function, node: &ast::FnDef) -> (Body, BodySourceMap) {
-        let mut collector = ExprCollector::new(DefWithBody::Function(function));
-        collector.collect_fn_body(node);
-        collector.finish()
-    }
    fn do_check_local_name(code: &str, expected_offset: u32) {
        let (off, code) = extract_offset(code);
-        let file = SourceFile::parse(&code);
+        let (db, _source_root, file_id) = MockDatabase::with_single_file(&code);
+        let file = db.parse(file_id);
        let expected_name = find_node_at_offset::<ast::Name>(file.syntax(), expected_offset.into())
            .expect("failed to find a name at the target offset");
-        let fn_def: &ast::FnDef = find_node_at_offset(file.syntax(), off).unwrap();
        let name_ref: &ast::NameRef = find_node_at_offset(file.syntax(), off).unwrap();
+        let analyzer = SourceAnalyzer::new(&db, file_id, name_ref.syntax(), None);
-        let irrelevant_function = Function { id: crate::ids::FunctionId::from_raw(0.into()) };
+        let local_name_entry = analyzer.resolve_local_name(name_ref).unwrap();
-        let (body, source_map) = collect_fn_body_syntax(irrelevant_function, fn_def);
+        let local_name =
-        let scopes = ExprScopes::new(Arc::new(body));
+            local_name_entry.ptr().either(|it| it.syntax_node_ptr(), |it| it.syntax_node_ptr());
-        let scopes =
-            ScopesWithSourceMap { scopes: Arc::new(scopes), source_map: Arc::new(source_map) };
-        let local_name_entry = scopes.resolve_local_name(name_ref).unwrap();
-        let local_name = local_name_entry.ptr();
        assert_eq!(local_name.range(), expected_name.syntax().range());
    }
diff --git a/crates/ra_hir/src/generics.rs b/crates/ra_hir/src/generics.rs
index 84fe94289..5625c2459 100644
--- a/crates/ra_hir/src/generics.rs
+++ b/crates/ra_hir/src/generics.rs
@@ -9,7 +9,7 @@ use ra_syntax::ast::{self, NameOwner, TypeParamsOwner};
 use crate::{
    db::DefDatabase,
-    Name, AsName, Function, Struct, Enum, Trait, TypeAlias, ImplBlock
+    Name, AsName, Function, Struct, Enum, Trait, TypeAlias, ImplBlock, Container
 };
 /// Data about a generic parameter (to a function, struct, impl, ...).
@@ -27,6 +27,7 @@ pub struct GenericParams {
    pub(crate) params: Vec<GenericParam>,
 }
+// FIXME: consts can have type parameters from their parents (i.e. associated consts of traits)
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
 pub enum GenericDef {
    Function(Function),
@@ -45,18 +46,22 @@ impl GenericParams {
    ) -> Arc<GenericParams> {
        let mut generics = GenericParams::default();
        let parent = match def {
-            GenericDef::Function(it) => it.impl_block(db),
+            GenericDef::Function(it) => it.container(db).map(GenericDef::from),
-            GenericDef::TypeAlias(it) => it.impl_block(db),
+            GenericDef::TypeAlias(it) => it.container(db).map(GenericDef::from),
            GenericDef::Struct(_) | GenericDef::Enum(_) | GenericDef::Trait(_) => None,
            GenericDef::ImplBlock(_) => None,
        };
-        generics.parent_params = parent.map(|p| p.generic_params(db));
+        generics.parent_params = parent.map(|p| db.generic_params(p));
        let start = generics.parent_params.as_ref().map(|p| p.params.len()).unwrap_or(0) as u32;
        match def {
            GenericDef::Function(it) => generics.fill(&*it.source(db).1, start),
            GenericDef::Struct(it) => generics.fill(&*it.source(db).1, start),
            GenericDef::Enum(it) => generics.fill(&*it.source(db).1, start),
-            GenericDef::Trait(it) => generics.fill(&*it.source(db).1, start),
+            GenericDef::Trait(it) => {
+                // traits get the Self type as an implicit first type parameter
+                generics.params.push(GenericParam { idx: start, name: Name::self_type() });
+                generics.fill(&*it.source(db).1, start + 1);
+            }
            GenericDef::TypeAlias(it) => generics.fill(&*it.source(db).1, start),
            GenericDef::ImplBlock(it) => generics.fill(&*it.source(db).1, start),
        }
@@ -104,3 +109,25 @@ impl GenericParams {
        vec
    }
 }
+impl From<Container> for GenericDef {
+    fn from(c: Container) -> Self {
+        match c {
+            Container::Trait(trait_) => trait_.into(),
+            Container::ImplBlock(impl_block) => impl_block.into(),
+        }
+    }
+}
+pub trait HasGenericParams {
+    fn generic_params(self, db: &impl DefDatabase) -> Arc<GenericParams>;
+}
+impl<T> HasGenericParams for T
+where
+    T: Into<GenericDef>,
+{
+    fn generic_params(self, db: &impl DefDatabase) -> Arc<GenericParams> {
+        db.generic_params(self.into())
+    }
+}
diff --git a/crates/ra_hir/src/ids.rs b/crates/ra_hir/src/ids.rs
index eb9939df7..141c9072f 100644
--- a/crates/ra_hir/src/ids.rs
+++ b/crates/ra_hir/src/ids.rs
@@ -3,40 +3,14 @@ use std::{
    sync::Arc,
 };
-use ra_db::{LocationInterner, FileId};
+use ra_db::{FileId, salsa};
 use ra_syntax::{TreeArc, SourceFile, AstNode, ast};
-use ra_arena::{RawId, ArenaId, impl_arena_id};
 use mbe::MacroRules;
 use crate::{
    Module, DefDatabase, AstId, FileAstId,
 };
-#[derive(Debug, Default)]
-pub struct HirInterner {
-    macros: LocationInterner<MacroCallLoc, MacroCallId>,
-    fns: LocationInterner<ItemLoc<ast::FnDef>, FunctionId>,
-    structs: LocationInterner<ItemLoc<ast::StructDef>, StructId>,
-    enums: LocationInterner<ItemLoc<ast::EnumDef>, EnumId>,
-    consts: LocationInterner<ItemLoc<ast::ConstDef>, ConstId>,
-    statics: LocationInterner<ItemLoc<ast::StaticDef>, StaticId>,
-    traits: LocationInterner<ItemLoc<ast::TraitDef>, TraitId>,
-    types: LocationInterner<ItemLoc<ast::TypeAliasDef>, TypeAliasId>,
-}
-impl HirInterner {
-    pub fn len(&self) -> usize {
-        self.macros.len()
-            + self.fns.len()
-            + self.structs.len()
-            + self.enums.len()
-            + self.consts.len()
-            + self.statics.len()
-            + self.traits.len()
-            + self.types.len()
-    }
-}
 /// hir makes heavy use of ids: integer (u32) handlers to various things. You
 /// can think of id as a pointer (but without a lifetime) or a file descriptor
 /// (but for hir objects).
@@ -135,11 +109,24 @@ pub(crate) fn macro_def_query(db: &impl DefDatabase, id: MacroDefId) -> Option<A
    Some(Arc::new(rules))
 }
+macro_rules! impl_intern_key {
+    ($name:ident) => {
+        impl salsa::InternKey for $name {
+            fn from_intern_id(v: salsa::InternId) -> Self {
+                $name(v)
+            }
+            fn as_intern_id(&self) -> salsa::InternId {
+                self.0
+            }
+        }
+    };
+}
 /// `MacroCallId` identifies a particular macro invocation, like
 /// `println!("Hello, {}", world)`.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct MacroCallId(RawId);
+pub struct MacroCallId(salsa::InternId);
-impl_arena_id!(MacroCallId);
+impl_intern_key!(MacroCallId);
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct MacroCallLoc {
@@ -148,14 +135,14 @@ pub struct MacroCallLoc {
 }
 impl MacroCallId {
-    pub(crate) fn loc(self, db: &impl AsRef<HirInterner>) -> MacroCallLoc {
+    pub(crate) fn loc(self, db: &impl DefDatabase) -> MacroCallLoc {
-        db.as_ref().macros.id2loc(self)
+        db.lookup_intern_macro(self)
    }
 }
 impl MacroCallLoc {
-    pub(crate) fn id(&self, db: &impl AsRef<HirInterner>) -> MacroCallId {
+    pub(crate) fn id(self, db: &impl DefDatabase) -> MacroCallId {
-        db.as_ref().macros.loc2id(&self)
+        db.intern_macro(self)
    }
 }
@@ -204,8 +191,10 @@ impl<'a, DB: DefDatabase> LocationCtx<&'a DB> {
    }
 }
-pub(crate) trait AstItemDef<N: AstNode>: ArenaId + Clone {
+pub(crate) trait AstItemDef<N: AstNode>: salsa::InternKey + Clone {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<N>, Self>;
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<N>) -> Self;
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<N>;
    fn from_ast(ctx: LocationCtx<&impl DefDatabase>, ast: &N) -> Self {
        let items = ctx.db.ast_id_map(ctx.file_id);
        let item_id = items.ast_id(ast);
@@ -213,80 +202,100 @@ pub(crate) trait AstItemDef<N: AstNode>: ArenaId + Clone {
    }
    fn from_ast_id(ctx: LocationCtx<&impl DefDatabase>, ast_id: FileAstId<N>) -> Self {
        let loc = ItemLoc { module: ctx.module, ast_id: ast_id.with_file_id(ctx.file_id) };
-        Self::interner(ctx.db.as_ref()).loc2id(&loc)
+        Self::intern(ctx.db, loc)
    }
    fn source(self, db: &impl DefDatabase) -> (HirFileId, TreeArc<N>) {
-        let int = Self::interner(db.as_ref());
+        let loc = self.lookup_intern(db);
-        let loc = int.id2loc(self);
        let ast = loc.ast_id.to_node(db);
        (loc.ast_id.file_id(), ast)
    }
    fn module(self, db: &impl DefDatabase) -> Module {
-        let int = Self::interner(db.as_ref());
+        let loc = self.lookup_intern(db);
-        let loc = int.id2loc(self);
        loc.module
    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) struct FunctionId(RawId);
+pub struct FunctionId(salsa::InternId);
-impl_arena_id!(FunctionId);
+impl_intern_key!(FunctionId);
 impl AstItemDef<ast::FnDef> for FunctionId {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::FnDef>, Self> {
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<ast::FnDef>) -> Self {
-        &interner.fns
+        db.intern_function(loc)
+    }
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<ast::FnDef> {
+        db.lookup_intern_function(self)
    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) struct StructId(RawId);
+pub struct StructId(salsa::InternId);
-impl_arena_id!(StructId);
+impl_intern_key!(StructId);
 impl AstItemDef<ast::StructDef> for StructId {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::StructDef>, Self> {
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<ast::StructDef>) -> Self {
-        &interner.structs
+        db.intern_struct(loc)
+    }
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<ast::StructDef> {
+        db.lookup_intern_struct(self)
    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) struct EnumId(RawId);
+pub struct EnumId(salsa::InternId);
-impl_arena_id!(EnumId);
+impl_intern_key!(EnumId);
 impl AstItemDef<ast::EnumDef> for EnumId {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::EnumDef>, Self> {
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<ast::EnumDef>) -> Self {
-        &interner.enums
+        db.intern_enum(loc)
+    }
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<ast::EnumDef> {
+        db.lookup_intern_enum(self)
    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) struct ConstId(RawId);
+pub struct ConstId(salsa::InternId);
-impl_arena_id!(ConstId);
+impl_intern_key!(ConstId);
 impl AstItemDef<ast::ConstDef> for ConstId {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::ConstDef>, Self> {
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<ast::ConstDef>) -> Self {
-        &interner.consts
+        db.intern_const(loc)
+    }
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<ast::ConstDef> {
+        db.lookup_intern_const(self)
    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) struct StaticId(RawId);
+pub struct StaticId(salsa::InternId);
-impl_arena_id!(StaticId);
+impl_intern_key!(StaticId);
 impl AstItemDef<ast::StaticDef> for StaticId {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::StaticDef>, Self> {
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<ast::StaticDef>) -> Self {
-        &interner.statics
+        db.intern_static(loc)
+    }
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<ast::StaticDef> {
+        db.lookup_intern_static(self)
    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) struct TraitId(RawId);
+pub struct TraitId(salsa::InternId);
-impl_arena_id!(TraitId);
+impl_intern_key!(TraitId);
 impl AstItemDef<ast::TraitDef> for TraitId {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::TraitDef>, Self> {
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<ast::TraitDef>) -> Self {
-        &interner.traits
+        db.intern_trait(loc)
+    }
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<ast::TraitDef> {
+        db.lookup_intern_trait(self)
    }
 }
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub(crate) struct TypeAliasId(RawId);
+pub struct TypeAliasId(salsa::InternId);
-impl_arena_id!(TypeAliasId);
+impl_intern_key!(TypeAliasId);
 impl AstItemDef<ast::TypeAliasDef> for TypeAliasId {
-    fn interner(interner: &HirInterner) -> &LocationInterner<ItemLoc<ast::TypeAliasDef>, Self> {
+    fn intern(db: &impl DefDatabase, loc: ItemLoc<ast::TypeAliasDef>) -> Self {
-        &interner.types
+        db.intern_type_alias(loc)
+    }
+    fn lookup_intern(self, db: &impl DefDatabase) -> ItemLoc<ast::TypeAliasDef> {
+        db.lookup_intern_type_alias(self)
    }
 }
diff --git a/crates/ra_hir/src/impl_block.rs b/crates/ra_hir/src/impl_block.rs
index 40d368cd9..a8a466e43 100644
--- a/crates/ra_hir/src/impl_block.rs
+++ b/crates/ra_hir/src/impl_block.rs
@@ -9,16 +9,15 @@ use ra_syntax::{
 use crate::{
    Const, TypeAlias, Function, HirFileId,
-    HirDatabase, DefDatabase,
+    HirDatabase, DefDatabase, TraitRef,
-    ModuleDef, Trait, Resolution,
    type_ref::TypeRef,
    ids::LocationCtx,
    resolve::Resolver,
-    ty::Ty, generics::GenericParams,
+    ty::Ty,
+    generics::HasGenericParams,
+    code_model_api::{Module, ModuleSource}
 };
-use crate::code_model_api::{Module, ModuleSource};
 #[derive(Debug, Default, PartialEq, Eq)]
 pub struct ImplSourceMap {
    map: ArenaMap<ImplId, AstPtr<ast::ImplBlock>>,
@@ -73,7 +72,7 @@ impl ImplBlock {
        self.module
    }
-    pub fn target_trait_ref(&self, db: &impl DefDatabase) -> Option<TypeRef> {
+    pub fn target_trait(&self, db: &impl DefDatabase) -> Option<TypeRef> {
        db.impls_in_module(self.module).impls[self.impl_id].target_trait().cloned()
    }
@@ -85,27 +84,16 @@ impl ImplBlock {
        Ty::from_hir(db, &self.resolver(db), &self.target_type(db))
    }
-    pub fn target_trait(&self, db: &impl HirDatabase) -> Option<Trait> {
+    pub fn target_trait_ref(&self, db: &impl HirDatabase) -> Option<TraitRef> {
-        if let Some(TypeRef::Path(path)) = self.target_trait_ref(db) {
+        let target_ty = self.target_ty(db);
-            let resolver = self.resolver(db);
+        TraitRef::from_hir(db, &self.resolver(db), &self.target_trait(db)?, Some(target_ty))
-            if let Some(Resolution::Def(ModuleDef::Trait(tr))) =
-                resolver.resolve_path(db, &path).take_types()
-            {
-                return Some(tr);
-            }
-        }
-        None
    }
    pub fn items(&self, db: &impl DefDatabase) -> Vec<ImplItem> {
        db.impls_in_module(self.module).impls[self.impl_id].items().to_vec()
    }
-    pub fn generic_params(&self, db: &impl DefDatabase) -> Arc<GenericParams> {
+    pub(crate) fn resolver(&self, db: &impl DefDatabase) -> Resolver {
-        db.generic_params((*self).into())
-    }
-    pub fn resolver(&self, db: &impl HirDatabase) -> Resolver {
        let r = self.module().resolver(db);
        // add generic params, if present
        let p = self.generic_params(db);
diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index c19450f39..9292de1b5 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -17,6 +17,8 @@ macro_rules! impl_froms {
    }
 }
+mod either;
 pub mod db;
 #[macro_use]
 pub mod mock;
@@ -49,20 +51,24 @@ use crate::{
    db::{HirDatabase, DefDatabase},
    name::{AsName, KnownName},
    source_id::{FileAstId, AstId},
+    resolve::Resolver,
 };
 pub use self::{
+    either::Either,
    path::{Path, PathKind},
    name::Name,
    source_id::{AstIdMap, ErasedFileAstId},
-    ids::{HirFileId, MacroDefId, MacroCallId, MacroCallLoc, HirInterner},
+    ids::{HirFileId, MacroDefId, MacroCallId, MacroCallLoc},
-    nameres::{PerNs, Namespace, ImportId, ImportSource},
+    nameres::{PerNs, Namespace, ImportId},
-    ty::{Ty, ApplicationTy, TypeCtor, Substs, display::HirDisplay},
+    ty::{Ty, ApplicationTy, TypeCtor, TraitRef, Substs, display::HirDisplay, CallableDef},
    impl_block::{ImplBlock, ImplItem},
    docs::{Docs, Documentation},
    adt::AdtDef,
-    expr::{ExprScopes, ScopesWithSourceMap, ScopeEntryWithSyntax},
+    expr::ExprScopes,
-    resolve::{Resolver, Resolution},
+    resolve::Resolution,
+    generics::{GenericParams, GenericParam, HasGenericParams},
+    source_binder::{SourceAnalyzer, PathResolution, ScopeEntryWithSyntax},
 };
 pub use self::code_model_api::{
@@ -73,5 +79,5 @@ pub use self::code_model_api::{
    Function, FnSignature,
    StructField, FieldSource,
    Static, Const, ConstSignature,
-    Trait, TypeAlias,
+    Trait, TypeAlias, Container,
 };
diff --git a/crates/ra_hir/src/mock.rs b/crates/ra_hir/src/mock.rs
index aeab6b180..fa5882dea 100644
--- a/crates/ra_hir/src/mock.rs
+++ b/crates/ra_hir/src/mock.rs
@@ -9,7 +9,7 @@ use relative_path::RelativePathBuf;
 use test_utils::{parse_fixture, CURSOR_MARKER, extract_offset};
 use rustc_hash::FxHashMap;
-use crate::{db, HirInterner, diagnostics::DiagnosticSink};
+use crate::{db, diagnostics::DiagnosticSink};
 pub const WORKSPACE: SourceRootId = SourceRootId(0);
@@ -18,7 +18,6 @@ pub const WORKSPACE: SourceRootId = SourceRootId(0);
 pub struct MockDatabase {
    events: Mutex<Option<Vec<salsa::Event<MockDatabase>>>>,
    runtime: salsa::Runtime<MockDatabase>,
-    interner: Arc<HirInterner>,
    files: FxHashMap<String, FileId>,
 }
@@ -195,7 +194,6 @@ impl Default for MockDatabase {
        let mut db = MockDatabase {
            events: Default::default(),
            runtime: salsa::Runtime::default(),
-            interner: Default::default(),
            files: FxHashMap::default(),
        };
        db.set_crate_graph(Default::default());
@@ -208,19 +206,12 @@ impl salsa::ParallelDatabase for MockDatabase {
        salsa::Snapshot::new(MockDatabase {
            events: Default::default(),
            runtime: self.runtime.snapshot(self),
-            interner: Arc::clone(&self.interner),
            // only the root database can be used to get file_id by path.
            files: FxHashMap::default(),
        })
    }
 }
-impl AsRef<HirInterner> for MockDatabase {
-    fn as_ref(&self) -> &HirInterner {
-        &self.interner
-    }
-}
 impl MockDatabase {
    pub fn log(&self, f: impl FnOnce()) -> Vec<salsa::Event<MockDatabase>> {
        *self.events.lock() = Some(Vec::new());
diff --git a/crates/ra_hir/src/nameres.rs b/crates/ra_hir/src/nameres.rs
index 4ae04514a..0eddfab12 100644
--- a/crates/ra_hir/src/nameres.rs
+++ b/crates/ra_hir/src/nameres.rs
@@ -75,7 +75,7 @@ pub(crate) use self::raw::{RawItems, ImportSourceMap};
 pub use self::{
    per_ns::{PerNs, Namespace},
-    raw::{ImportId, ImportSource},
+    raw::ImportId,
 };
 /// Contans all top-level defs from a macro-expanded crate
diff --git a/crates/ra_hir/src/nameres/raw.rs b/crates/ra_hir/src/nameres/raw.rs
index b7416ede6..43c97a0bf 100644
--- a/crates/ra_hir/src/nameres/raw.rs
+++ b/crates/ra_hir/src/nameres/raw.rs
@@ -12,7 +12,7 @@ use ra_syntax::{
 use crate::{
    DefDatabase, Name, AsName, Path, HirFileId, ModuleSource,
-    AstIdMap, FileAstId,
+    AstIdMap, FileAstId, Either,
 };
 /// `RawItems` is a set of top-level items in a file (except for impls).
@@ -34,28 +34,15 @@ pub struct ImportSourceMap {
    map: ArenaMap<ImportId, ImportSourcePtr>,
 }
-#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+type ImportSourcePtr = Either<AstPtr<ast::UseTree>, AstPtr<ast::ExternCrateItem>>;
-enum ImportSourcePtr {
+type ImportSource = Either<TreeArc<ast::UseTree>, TreeArc<ast::ExternCrateItem>>;
-    UseTree(AstPtr<ast::UseTree>),
-    ExternCrate(AstPtr<ast::ExternCrateItem>),
-}
 impl ImportSourcePtr {
    fn to_node(self, file: &SourceFile) -> ImportSource {
-        match self {
+        self.map(|ptr| ptr.to_node(file).to_owned(), |ptr| ptr.to_node(file).to_owned())
-            ImportSourcePtr::UseTree(ptr) => ImportSource::UseTree(ptr.to_node(file).to_owned()),
-            ImportSourcePtr::ExternCrate(ptr) => {
-                ImportSource::ExternCrate(ptr.to_node(file).to_owned())
-            }
-        }
    }
 }
-pub enum ImportSource {
-    UseTree(TreeArc<ast::UseTree>),
-    ExternCrate(TreeArc<ast::ExternCrateItem>),
-}
 impl ImportSourceMap {
    fn insert(&mut self, import: ImportId, ptr: ImportSourcePtr) {
        self.map.insert(import, ptr)
@@ -281,11 +268,7 @@ impl RawItemsCollector {
        Path::expand_use_item(use_item, |path, use_tree, is_glob, alias| {
            let import_data =
                ImportData { path, alias, is_glob, is_prelude, is_extern_crate: false };
-            self.push_import(
+            self.push_import(current_module, import_data, Either::A(AstPtr::new(use_tree)));
-                current_module,
-                import_data,
-                ImportSourcePtr::UseTree(AstPtr::new(use_tree)),
-            );
        })
    }
@@ -304,11 +287,7 @@ impl RawItemsCollector {
                is_prelude: false,
                is_extern_crate: true,
            };
-            self.push_import(
+            self.push_import(current_module, import_data, Either::B(AstPtr::new(extern_crate)));
-                current_module,
-                import_data,
-                ImportSourcePtr::ExternCrate(AstPtr::new(extern_crate)),
-            );
        }
    }
diff --git a/crates/ra_hir/src/resolve.rs b/crates/ra_hir/src/resolve.rs
index 2609585b1..685f4b8b1 100644
--- a/crates/ra_hir/src/resolve.rs
+++ b/crates/ra_hir/src/resolve.rs
@@ -9,13 +9,13 @@ use crate::{
    name::{Name, KnownName},
    nameres::{PerNs, CrateDefMap, CrateModuleId},
    generics::GenericParams,
-    expr::{scope::{ExprScopes, ScopeId}, PatId, Body},
+    expr::{scope::{ExprScopes, ScopeId}, PatId},
    impl_block::ImplBlock,
    path::Path, Trait
 };
 #[derive(Debug, Clone, Default)]
-pub struct Resolver {
+pub(crate) struct Resolver {
    scopes: Vec<Scope>,
 }
@@ -117,7 +117,7 @@ pub enum Resolution {
 }
 impl Resolver {
-    pub fn resolve_name(&self, db: &impl HirDatabase, name: &Name) -> PerNs<Resolution> {
+    pub(crate) fn resolve_name(&self, db: &impl HirDatabase, name: &Name) -> PerNs<Resolution> {
        let mut resolution = PerNs::none();
        for scope in self.scopes.iter().rev() {
            resolution = resolution.or(scope.resolve_name(db, name));
@@ -154,12 +154,12 @@ impl Resolver {
    /// Returns the fully resolved path if we were able to resolve it.
    /// otherwise returns `PerNs::none`
-    pub fn resolve_path(&self, db: &impl HirDatabase, path: &Path) -> PerNs<Resolution> {
+    pub(crate) fn resolve_path(&self, db: &impl HirDatabase, path: &Path) -> PerNs<Resolution> {
        // into_fully_resolved() returns the fully resolved path or PerNs::none() otherwise
        self.resolve_path_segments(db, path).into_fully_resolved()
    }
-    pub fn all_names(&self, db: &impl HirDatabase) -> FxHashMap<Name, PerNs<Resolution>> {
+    pub(crate) fn all_names(&self, db: &impl HirDatabase) -> FxHashMap<Name, PerNs<Resolution>> {
        let mut names = FxHashMap::default();
        for scope in self.scopes.iter().rev() {
            scope.collect_names(db, &mut |name, res| {
@@ -197,14 +197,6 @@ impl Resolver {
            _ => None,
        })
    }
-    /// The body from which any `LocalBinding` resolutions in this resolver come.
-    pub fn body(&self) -> Option<Arc<Body>> {
-        self.scopes.iter().rev().find_map(|scope| match scope {
-            Scope::ExprScope(expr_scope) => Some(expr_scope.expr_scopes.body()),
-            _ => None,
-        })
-    }
 }
 impl Resolver {
diff --git a/crates/ra_hir/src/source_binder.rs b/crates/ra_hir/src/source_binder.rs
index 182ed4c91..bd035ced9 100644
--- a/crates/ra_hir/src/source_binder.rs
+++ b/crates/ra_hir/src/source_binder.rs
@@ -5,16 +5,21 @@
 ///
 /// So, this modules should not be used during hir construction, it exists
 /// purely for "IDE needs".
+use std::sync::Arc;
+use rustc_hash::{FxHashSet, FxHashMap};
 use ra_db::{FileId, FilePosition};
 use ra_syntax::{
-    SyntaxNode,
+    SyntaxNode, AstPtr, TextUnit, SyntaxNodePtr, TextRange,
    ast::{self, AstNode, NameOwner},
-    algo::{find_node_at_offset, find_token_at_offset},
+    algo::find_node_at_offset,
+    SyntaxKind::*,
 };
 use crate::{
-    HirDatabase, Function, Struct, Enum,Const,Static,
+    HirDatabase, Function, Struct, Enum, Const, Static, Either, DefWithBody, PerNs, Name,
    AsName, Module, HirFileId, Crate, Trait, Resolver,
+    expr::{BodySourceMap, scope::{ScopeId, ExprScopes}},
    ids::LocationCtx,
    expr, AstId
 };
@@ -87,63 +92,6 @@ fn module_from_source(
    )
 }
-pub fn const_from_source(
-    db: &impl HirDatabase,
-    file_id: FileId,
-    const_def: &ast::ConstDef,
-) -> Option<Const> {
-    let module = module_from_child_node(db, file_id, const_def.syntax())?;
-    let res = const_from_module(db, module, const_def);
-    Some(res)
-}
-pub fn const_from_module(
-    db: &impl HirDatabase,
-    module: Module,
-    const_def: &ast::ConstDef,
-) -> Const {
-    let (file_id, _) = module.definition_source(db);
-    let file_id = file_id.into();
-    let ctx = LocationCtx::new(db, module, file_id);
-    Const { id: ctx.to_def(const_def) }
-}
-pub fn function_from_position(db: &impl HirDatabase, position: FilePosition) -> Option<Function> {
-    let file = db.parse(position.file_id);
-    let fn_def = find_node_at_offset::<ast::FnDef>(file.syntax(), position.offset)?;
-    function_from_source(db, position.file_id, fn_def)
-}
-pub fn function_from_source(
-    db: &impl HirDatabase,
-    file_id: FileId,
-    fn_def: &ast::FnDef,
-) -> Option<Function> {
-    let module = module_from_child_node(db, file_id, fn_def.syntax())?;
-    let res = function_from_module(db, module, fn_def);
-    Some(res)
-}
-pub fn function_from_module(
-    db: &impl HirDatabase,
-    module: Module,
-    fn_def: &ast::FnDef,
-) -> Function {
-    let (file_id, _) = module.definition_source(db);
-    let file_id = file_id.into();
-    let ctx = LocationCtx::new(db, module, file_id);
-    Function { id: ctx.to_def(fn_def) }
-}
-pub fn function_from_child_node(
-    db: &impl HirDatabase,
-    file_id: FileId,
-    node: &SyntaxNode,
-) -> Option<Function> {
-    let fn_def = node.ancestors().find_map(ast::FnDef::cast)?;
-    function_from_source(db, file_id, fn_def)
-}
 pub fn struct_from_module(
    db: &impl HirDatabase,
    module: Module,
@@ -155,27 +103,6 @@ pub fn struct_from_module(
    Struct { id: ctx.to_def(struct_def) }
 }
-pub fn static_from_source(
-    db: &impl HirDatabase,
-    file_id: FileId,
-    static_def: &ast::StaticDef,
-) -> Option<Static> {
-    let module = module_from_child_node(db, file_id, static_def.syntax())?;
-    let res = static_from_module(db, module, static_def);
-    Some(res)
-}
-pub fn static_from_module(
-    db: &impl HirDatabase,
-    module: Module,
-    static_def: &ast::StaticDef,
-) -> Static {
-    let (file_id, _) = module.definition_source(db);
-    let file_id = file_id.into();
-    let ctx = LocationCtx::new(db, module, file_id);
-    Static { id: ctx.to_def(static_def) }
-}
 pub fn enum_from_module(db: &impl HirDatabase, module: Module, enum_def: &ast::EnumDef) -> Enum {
    let (file_id, _) = module.definition_source(db);
    let file_id = file_id.into();
@@ -194,48 +121,6 @@ pub fn trait_from_module(
    Trait { id: ctx.to_def(trait_def) }
 }
-pub fn resolver_for_position(db: &impl HirDatabase, position: FilePosition) -> Resolver {
-    let file_id = position.file_id;
-    let file = db.parse(file_id);
-    find_token_at_offset(file.syntax(), position.offset)
-        .find_map(|token| {
-            token.parent().ancestors().find_map(|node| {
-                if ast::Expr::cast(node).is_some() || ast::Block::cast(node).is_some() {
-                    if let Some(func) = function_from_child_node(db, file_id, node) {
-                        let scopes = func.scopes(db);
-                        let scope = scopes.scope_for_offset(position.offset);
-                        Some(expr::resolver_for_scope(func.body(db), db, scope))
-                    } else {
-                        // FIXME const/static/array length
-                        None
-                    }
-                } else {
-                    try_get_resolver_for_node(db, file_id, node)
-                }
-            })
-        })
-        .unwrap_or_default()
-}
-pub fn resolver_for_node(db: &impl HirDatabase, file_id: FileId, node: &SyntaxNode) -> Resolver {
-    node.ancestors()
-        .find_map(|node| {
-            if ast::Expr::cast(node).is_some() || ast::Block::cast(node).is_some() {
-                if let Some(func) = function_from_child_node(db, file_id, node) {
-                    let scopes = func.scopes(db);
-                    let scope = scopes.scope_for(&node);
-                    Some(expr::resolver_for_scope(func.body(db), db, scope))
-                } else {
-                    // FIXME const/static/array length
-                    None
-                }
-            } else {
-                try_get_resolver_for_node(db, file_id, node)
-            }
-        })
-        .unwrap_or_default()
-}
 fn try_get_resolver_for_node(
    db: &impl HirDatabase,
    file_id: FileId,
@@ -251,10 +136,281 @@ fn try_get_resolver_for_node(
    } else if let Some(e) = ast::EnumDef::cast(node) {
        let module = module_from_child_node(db, file_id, e.syntax())?;
        Some(enum_from_module(db, module, e).resolver(db))
-    } else if let Some(f) = ast::FnDef::cast(node) {
+    } else if node.kind() == FN_DEF || node.kind() == CONST_DEF || node.kind() == STATIC_DEF {
-        function_from_source(db, file_id, f).map(|f| f.resolver(db))
+        Some(def_with_body_from_child_node(db, file_id, node)?.resolver(db))
    } else {
        // FIXME add missing cases
        None
    }
 }
+fn def_with_body_from_child_node(
+    db: &impl HirDatabase,
+    file_id: FileId,
+    node: &SyntaxNode,
+) -> Option<DefWithBody> {
+    let module = module_from_child_node(db, file_id, node)?;
+    let ctx = LocationCtx::new(db, module, file_id.into());
+    node.ancestors().find_map(|node| {
+        if let Some(def) = ast::FnDef::cast(node) {
+            return Some(Function { id: ctx.to_def(def) }.into());
+        }
+        if let Some(def) = ast::ConstDef::cast(node) {
+            return Some(Const { id: ctx.to_def(def) }.into());
+        }
+        if let Some(def) = ast::StaticDef::cast(node) {
+            return Some(Static { id: ctx.to_def(def) }.into());
+        }
+        None
+    })
+}
+/// `SourceAnalyzer` is a convenience wrapper which exposes HIR API in terms of
+/// original source files. It should not be used inside the HIR itself.
+#[derive(Debug)]
+pub struct SourceAnalyzer {
+    resolver: Resolver,
+    body_source_map: Option<Arc<BodySourceMap>>,
+    infer: Option<Arc<crate::ty::InferenceResult>>,
+    scopes: Option<Arc<crate::expr::ExprScopes>>,
+}
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum PathResolution {
+    /// An item
+    Def(crate::ModuleDef),
+    /// A local binding (only value namespace)
+    LocalBinding(Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>>),
+    /// A generic parameter
+    GenericParam(u32),
+    SelfType(crate::ImplBlock),
+    AssocItem(crate::ImplItem),
+}
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ScopeEntryWithSyntax {
+    pub(crate) name: Name,
+    pub(crate) ptr: Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>>,
+}
+impl ScopeEntryWithSyntax {
+    pub fn name(&self) -> &Name {
+        &self.name
+    }
+    pub fn ptr(&self) -> Either<AstPtr<ast::Pat>, AstPtr<ast::SelfParam>> {
+        self.ptr
+    }
+}
+#[derive(Debug)]
+pub struct ReferenceDescriptor {
+    pub range: TextRange,
+    pub name: String,
+}
+impl SourceAnalyzer {
+    pub fn new(
+        db: &impl HirDatabase,
+        file_id: FileId,
+        node: &SyntaxNode,
+        offset: Option<TextUnit>,
+    ) -> SourceAnalyzer {
+        let def_with_body = def_with_body_from_child_node(db, file_id, node);
+        if let Some(def) = def_with_body {
+            let source_map = def.body_source_map(db);
+            let scopes = db.expr_scopes(def);
+            let scope = match offset {
+                None => scope_for(&scopes, &source_map, &node),
+                Some(offset) => scope_for_offset(&scopes, &source_map, offset),
+            };
+            let resolver = expr::resolver_for_scope(def.body(db), db, scope);
+            SourceAnalyzer {
+                resolver,
+                body_source_map: Some(source_map),
+                infer: Some(def.infer(db)),
+                scopes: Some(scopes),
+            }
+        } else {
+            SourceAnalyzer {
+                resolver: node
+                    .ancestors()
+                    .find_map(|node| try_get_resolver_for_node(db, file_id, node))
+                    .unwrap_or_default(),
+                body_source_map: None,
+                infer: None,
+                scopes: None,
+            }
+        }
+    }
+    pub fn type_of(&self, _db: &impl HirDatabase, expr: &ast::Expr) -> Option<crate::Ty> {
+        let expr_id = self.body_source_map.as_ref()?.node_expr(expr)?;
+        Some(self.infer.as_ref()?[expr_id].clone())
+    }
+    pub fn type_of_pat(&self, _db: &impl HirDatabase, pat: &ast::Pat) -> Option<crate::Ty> {
+        let pat_id = self.body_source_map.as_ref()?.node_pat(pat)?;
+        Some(self.infer.as_ref()?[pat_id].clone())
+    }
+    pub fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
+        let expr_id = self.body_source_map.as_ref()?.node_expr(call.into())?;
+        self.infer.as_ref()?.method_resolution(expr_id)
+    }
+    pub fn resolve_field(&self, field: &ast::FieldExpr) -> Option<crate::StructField> {
+        let expr_id = self.body_source_map.as_ref()?.node_expr(field.into())?;
+        self.infer.as_ref()?.field_resolution(expr_id)
+    }
+    pub fn resolve_hir_path(
+        &self,
+        db: &impl HirDatabase,
+        path: &crate::Path,
+    ) -> PerNs<crate::Resolution> {
+        self.resolver.resolve_path(db, path)
+    }
+    pub fn resolve_path(&self, db: &impl HirDatabase, path: &ast::Path) -> Option<PathResolution> {
+        if let Some(path_expr) = path.syntax().parent().and_then(ast::PathExpr::cast) {
+            let expr_id = self.body_source_map.as_ref()?.node_expr(path_expr.into())?;
+            if let Some(assoc) = self.infer.as_ref()?.assoc_resolutions_for_expr(expr_id) {
+                return Some(PathResolution::AssocItem(assoc));
+            }
+        }
+        if let Some(path_pat) = path.syntax().parent().and_then(ast::PathPat::cast) {
+            let pat_id = self.body_source_map.as_ref()?.node_pat(path_pat.into())?;
+            if let Some(assoc) = self.infer.as_ref()?.assoc_resolutions_for_pat(pat_id) {
+                return Some(PathResolution::AssocItem(assoc));
+            }
+        }
+        let hir_path = crate::Path::from_ast(path)?;
+        let res = self.resolver.resolve_path(db, &hir_path);
+        let res = res.clone().take_types().or_else(|| res.take_values())?;
+        let res = match res {
+            crate::Resolution::Def(it) => PathResolution::Def(it),
+            crate::Resolution::LocalBinding(it) => {
+                PathResolution::LocalBinding(self.body_source_map.as_ref()?.pat_syntax(it)?)
+            }
+            crate::Resolution::GenericParam(it) => PathResolution::GenericParam(it),
+            crate::Resolution::SelfType(it) => PathResolution::SelfType(it),
+        };
+        Some(res)
+    }
+    pub fn resolve_local_name(&self, name_ref: &ast::NameRef) -> Option<ScopeEntryWithSyntax> {
+        let mut shadowed = FxHashSet::default();
+        let name = name_ref.as_name();
+        let source_map = self.body_source_map.as_ref()?;
+        let scopes = self.scopes.as_ref()?;
+        let scope = scope_for(scopes, source_map, name_ref.syntax());
+        let ret = scopes
+            .scope_chain(scope)
+            .flat_map(|scope| scopes.entries(scope).iter())
+            .filter(|entry| shadowed.insert(entry.name()))
+            .filter(|entry| entry.name() == &name)
+            .nth(0);
+        ret.and_then(|entry| {
+            Some(ScopeEntryWithSyntax {
+                name: entry.name().clone(),
+                ptr: source_map.pat_syntax(entry.pat())?,
+            })
+        })
+    }
+    pub fn all_names(&self, db: &impl HirDatabase) -> FxHashMap<Name, PerNs<crate::Resolution>> {
+        self.resolver.all_names(db)
+    }
+    pub fn find_all_refs(&self, pat: &ast::BindPat) -> Vec<ReferenceDescriptor> {
+        // FIXME: at least, this should work with any DefWithBody, but ideally
+        // this should be hir-based altogether
+        let fn_def = pat.syntax().ancestors().find_map(ast::FnDef::cast).unwrap();
+        let ptr = Either::A(AstPtr::new(pat.into()));
+        fn_def
+            .syntax()
+            .descendants()
+            .filter_map(ast::NameRef::cast)
+            .filter(|name_ref| match self.resolve_local_name(*name_ref) {
+                None => false,
+                Some(entry) => entry.ptr() == ptr,
+            })
+            .map(|name_ref| ReferenceDescriptor {
+                name: name_ref.text().to_string(),
+                range: name_ref.syntax().range(),
+            })
+            .collect()
+    }
+    #[cfg(test)]
+    pub(crate) fn body_source_map(&self) -> Arc<BodySourceMap> {
+        self.body_source_map.clone().unwrap()
+    }
+    #[cfg(test)]
+    pub(crate) fn inference_result(&self) -> Arc<crate::ty::InferenceResult> {
+        self.infer.clone().unwrap()
+    }
+    #[cfg(test)]
+    pub(crate) fn scopes(&self) -> Arc<ExprScopes> {
+        self.scopes.clone().unwrap()
+    }
+}
+fn scope_for(
+    scopes: &ExprScopes,
+    source_map: &BodySourceMap,
+    node: &SyntaxNode,
+) -> Option<ScopeId> {
+    node.ancestors()
+        .map(SyntaxNodePtr::new)
+        .filter_map(|ptr| source_map.syntax_expr(ptr))
+        .find_map(|it| scopes.scope_for(it))
+}
+fn scope_for_offset(
+    scopes: &ExprScopes,
+    source_map: &BodySourceMap,
+    offset: TextUnit,
+) -> Option<ScopeId> {
+    scopes
+        .scope_by_expr()
+        .iter()
+        .filter_map(|(id, scope)| Some((source_map.expr_syntax(*id)?, scope)))
+        // find containing scope
+        .min_by_key(|(ptr, _scope)| {
+            (!(ptr.range().start() <= offset && offset <= ptr.range().end()), ptr.range().len())
+        })
+        .map(|(ptr, scope)| adjust(scopes, source_map, ptr, offset).unwrap_or(*scope))
+}
+// XXX: during completion, cursor might be outside of any particular
+// expression. Try to figure out the correct scope...
+fn adjust(
+    scopes: &ExprScopes,
+    source_map: &BodySourceMap,
+    ptr: SyntaxNodePtr,
+    offset: TextUnit,
+) -> Option<ScopeId> {
+    let r = ptr.range();
+    let child_scopes = scopes
+        .scope_by_expr()
+        .iter()
+        .filter_map(|(id, scope)| Some((source_map.expr_syntax(*id)?, scope)))
+        .map(|(ptr, scope)| (ptr.range(), scope))
+        .filter(|(range, _)| range.start() <= offset && range.is_subrange(&r) && *range != r);
+    child_scopes
+        .max_by(|(r1, _), (r2, _)| {
+            if r2.is_subrange(&r1) {
+                std::cmp::Ordering::Greater
+            } else if r1.is_subrange(&r2) {
+                std::cmp::Ordering::Less
+            } else {
+                r1.start().cmp(&r2.start())
+            }
+        })
+        .map(|(_ptr, scope)| *scope)
+}
diff --git a/crates/ra_hir/src/traits.rs b/crates/ra_hir/src/traits.rs
index 725bdd5cb..15f0977b7 100644
--- a/crates/ra_hir/src/traits.rs
+++ b/crates/ra_hir/src/traits.rs
@@ -1,10 +1,11 @@
 //! HIR for trait definitions.
 use std::sync::Arc;
+use rustc_hash::FxHashMap;
 use ra_syntax::ast::{self, NameOwner};
-use crate::{Function, Const, TypeAlias, Name, DefDatabase, Trait, ids::LocationCtx, name::AsName};
+use crate::{Function, Const, TypeAlias, Name, DefDatabase, Trait, ids::LocationCtx, name::AsName, Module};
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct TraitData {
@@ -49,4 +50,34 @@ pub enum TraitItem {
    TypeAlias(TypeAlias),
    // Existential
 }
+// FIXME: not every function, ... is actually a trait item. maybe we should make
+// sure that you can only turn actual trait items into TraitItems. This would
+// require not implementing From, and instead having some checked way of
+// casting them.
 impl_froms!(TraitItem: Function, Const, TypeAlias);
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct TraitItemsIndex {
+    traits_by_def: FxHashMap<TraitItem, Trait>,
+}
+impl TraitItemsIndex {
+    pub(crate) fn trait_items_index(db: &impl DefDatabase, module: Module) -> TraitItemsIndex {
+        let mut index = TraitItemsIndex { traits_by_def: FxHashMap::default() };
+        for decl in module.declarations(db) {
+            match decl {
+                crate::ModuleDef::Trait(tr) => {
+                    for item in tr.trait_data(db).items() {
+                        index.traits_by_def.insert(*item, tr);