3 files changed, 36 insertions, 4 deletions

diff --git a/Cargo.lock b/Cargo.lock
index e38fa0ff0..4dbe5679d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -41,7 +41,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "backtrace"
-version = "0.3.26"
+version = "0.3.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -381,7 +381,7 @@ name = "error-chain"
 version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace 0.3.26 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -390,7 +390,7 @@ name = "failure"
 version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace 0.3.26 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "failure_derive 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1179,6 +1179,7 @@ dependencies = [
 name = "ra_prof"
 version = "0.1.0"
 dependencies = [
+ "backtrace 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "once_cell 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1986,7 +1987,7 @@ dependencies = [
 "checksum arrayvec 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)" = "92c7fb76bc8826a8b33b4ee5bb07a247a81e76764ab4d55e8f73e3a4d8808c71"
 "checksum atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "9a7d5b8723950951411ee34d271d99dddcc2035a16ab25310ea2c8cfd4369652"
 "checksum autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "0e49efa51329a5fd37e7c79db4621af617cd4e3e5bc224939808d076077077bf"
-"checksum backtrace 0.3.26 (registry+https://github.com/rust-lang/crates.io-index)" = "1a13fc43f04daf08ab4f71e3d27e1fc27fc437d3e95ac0063a796d92fb40f39b"
+"checksum backtrace 0.3.28 (registry+https://github.com/rust-lang/crates.io-index)" = "d0c18049b371fef38d66b2d69643618023d9d6b4e62891019f3359e88f73922a"
 "checksum backtrace-sys 0.1.28 (registry+https://github.com/rust-lang/crates.io-index)" = "797c830ac25ccc92a7f8a7b9862bde440715531514594a6154e3d4a54dd769b6"
 "checksum base64 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0b25d992356d2eb0ed82172f5248873db5560c4721f564b13cb5193bda5e668e"
 "checksum bit-set 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "e84c238982c4b1e1ee668d136c510c67a13465279c0cb367ea6baf6310620a80"
diff --git a/crates/ra_prof/Cargo.toml b/crates/ra_prof/Cargo.toml
index efcce3d65..d55af18f5 100644
--- a/crates/ra_prof/Cargo.toml
+++ b/crates/ra_prof/Cargo.toml
@@ -8,3 +8,4 @@ publish = false
 [dependencies]
 once_cell = "0.2.0"
 itertools = "0.8.0"
+backtrace = "0.3.28"
diff --git a/crates/ra_prof/src/lib.rs b/crates/ra_prof/src/lib.rs
index e681b8e0b..6ec24d86d 100644
--- a/crates/ra_prof/src/lib.rs
+++ b/crates/ra_prof/src/lib.rs
@@ -225,6 +225,36 @@ fn print(lvl: usize, msgs: &[Message], out: &mut impl Write, longer_than: Durati
     }
 }
 
+/// Prints backtrace to stderr, useful for debugging.
+pub fn print_backtrace() {
+    let bt = backtrace::Backtrace::new();
+    eprintln!("{:?}", bt);
+}
+
+thread_local!(static IN_SCOPE: RefCell<bool> = RefCell::new(false));
+
+/// Allows to check if the current code is withing some dynamic scope, can be
+/// useful during debugging to figure out why a function is called.
+pub struct Scope {
+    _hidden: (),
+}
+
+impl Scope {
+    pub fn enter() -> Scope {
+        IN_SCOPE.with(|slot| *slot.borrow_mut() = true);
+        Scope { _hidden: () }
+    }
+    pub fn is_active() -> bool {
+        IN_SCOPE.with(|slot| *slot.borrow())
+    }
+}
+
+impl Drop for Scope {
+    fn drop(&mut self) {
+        IN_SCOPE.with(|slot| *slot.borrow_mut() = false);
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;