Cleanup nll

[ljedrz]

• improve allocations
• improve format! calls
• improve common patterns

[rust-highfive]

r? @estebank

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[Mark-Simulacrum]

Hm, I'd rather make this change in a separate PR which would be benchmarked to make sure this is actually an optimization (it looks like it would be but I'm not sure).

[estebank]

LGTM, after addressing @Mark-Simulacrum's comments.

[ljedrz]

@estebank comments addressed.

[rust-highfive]

The job x86_64-gnu-llvm-5.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:53:55] .................................................................................................... 4200/4622
[00:53:58] ......i............................................................................................. 4300/4622
[00:54:02] .................................................................................................... 4400/4622
[00:54:05] .................................................................................................... 4500/4622
= Foo { x: None };\nx.x = Some(&y);\n```\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/nll/polonius-smoke-test.rs","byte_start":199,"byte_end":201,"line_start":7,"line_end":7,"column_start":5,"column_end":7,"is_primary":true,"text":[{"text":"    &x //~ ERROR","highlight_start":5,"highlight_end":7}],"label":"borrowed value does not live long enough","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"/checkout/src/test/ui/nll/polonius-smoke-test.rs","byte_start":212,"byte_end":213,"line_start":8,"line_end":8,"column_start":1,"column_end":2,"is_primary":false,"text":[{"text":"}","highlight_start":1,"highlight_end":2}],"label":"`x` dropped here while still borrowed","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"borrowed value must be valid for the static lifetime...","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"error[E0597]: `x` does not live long enough\n  --> /checkout/src/test/ui/nll/polonius-smoke-test.rs:7:5\n   |\nLL |     &x //~ ERROR\n   |     ^^ borrowed value does not live long enough\nLL | }\n   | - `x` dropped here while still borrowed\n   |\n   = note: borrowed value must be valid for the static lifetime...\n\n"}
[00:54:08] {"message":"cannot use `x` because it was mutably borrowed","code":{"code":"E0503","explanation":"\nA value was used after it was mutably borrowed.\n\nExample of erroneous code:\n\n```compile_fail,E0503\nfn main() {\n    let mut value = 3;\n    // Create a mutable borrow of `value`. This borrow\n    // lives until the end of this function.\n  to `_ref_to_val`.\nTo fix that you can do few different things:\n\n* Try to avoid moving the variable.\n* Release borrow before move.\n* Implement the `Copy` trait on the type.\n\nExamples:\n\n```\nstruct Value {}\n\nfn eat(val: &Value) {}\n\nfn main() {\n    let x = Value{};\n    {\n        let _ref_to_val: &Value = &x;\n        eat(&x); // pass by reference, if it's possible\n    }\n}\n```\n\nOr:\n\n```\nstruct Value {}\n\nfn eat(val: Value) {}\n\nfn main() {\n    let x = Value{};\n    {\n        let _ref_to_val: &Value = &x;\n    }\n    eat(x); // release borrow and then move it.\n}\n```\n\nOr:\n\n```\n#[derive(Clone, Copy)] // implement Copy trait\nstruct Value {}\n\nfn eat(val: Value) {}\n\nfn main() {\n    let x = Value{};\n    {\n        let _ref_to_val: &Value = &x;\n        eat(x); // it will be copied here.\n    }\n}\n```\n\nYou can find more information about borrowing in the rust-book:\nhttp://doc.rust-lang.org/stable/book/references-and-borrowing.html\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/nll/polonius-smoke-test.rs","byte_start":385,"byte_end":392,"line_start":18,"line_end":18,"column_start":13,"column_end":20,"is_primary":false,"text":[{"text":"    let y = &mut *x;","highlight_start":13,"highlight_end":20}],"label":"borrow of `*x` occurs here","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"/checkout/src/test/ui/nll/polonius-smoke-test.rs","byte_start":406,"byte_end":407,"line_start":19,"line_end":19,"column_start":13,"column_end":14,"is_primary":true,"text":[{"text":"    let z = x; //~ ERROR","highlight_start":13,"highlight_end":14}],"labelr a backtrace.
[00:54:08] 
[00:54:08] failures:
[00:54:08]     [ui] ui/nll/polonius-smoke-test.rs
[00:54:08] 
[00:54:08] 
[00:54:08] test result: FAILED. 4601 passed; 1 failed; 20 ignored; 0 measured; 0 filtered out
[00:54:08] 
[00:54:08] thread 'main' panicked at 'Some tests failed', tools/compiletest/src/main.rs:501:22
[00:54:08] 
[00:54:08] 
[00:54:08] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-5.0/bin/FileCheck" "--host-rustcflags" "-Crpath -O -Zunstable-options " "--target-rustcflags" "-Crpath -O -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "5.0.0\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
[00:54:08] 
[00:54:08] 
[0
travis_time:end:220c9c90:start=1539800773144546658,finish=1539804021692434916,duration=3248547888258

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[estebank]

[00:54:08] ---- [ui] ui/nll/polonius-smoke-test.rs stdout ----
[00:54:08] diff of stderr:
[00:54:08] 
[00:54:08] 28	LL |     y
[00:54:08] 29	   |     - borrow later used here
[00:54:08] 30	
[00:54:08] -	error[E0505]: cannot move out of `s` because it is borrowed
[00:54:08] -	  --> $DIR/polonius-smoke-test.rs:43:5
[00:54:08] -	   |
[00:54:08] -	LL |     let r = &mut *s;
[00:54:08] -	   |             ------- borrow of `*s` occurs here
[00:54:08] -	LL |     let tmp = foo(&r);
[00:54:08] -	LL |     s; //~ ERROR
[00:54:08] -	   |     ^ move out of `s` occurs here
[00:54:08] -	LL |     tmp;
[00:54:08] -	   |     --- borrow later used here
[00:54:08] -	
[00:54:08] -	error: aborting due to 4 previous errors
[00:54:08] +	error: aborting due to 3 previous errors
[00:54:08] 43	
[00:54:08] 44	Some errors occurred: E0503, E0505, E0597.
[00:54:08] 45	For more information about an error, try `rustc --explain E0503`.

[ljedrz]

Yes, but how? I only changed size_hint to count (plus the related iterator stuff).

[Mark-Simulacrum]

Count will exhaust the iterator (by_ref doesn't clone it) regardless of whether it's implemented to be more efficient, I believe.

[estebank]

@bors r+ rollup

[bors]

📌 Commit ffecbc5 has been approved by estebank