don't ask what edition we are in; ask what edition a span is in

[nikomatsakis]

We now track the edition of each span. Using that info when gating the Rust 2018 interpretation means that macros from Rust 2015 crates "just work" when used in Rust 2018 crates (at least in the case of use paths).

Fixes #50172

r? @petrochenkov

cc @Manishearth @alexcrichton

[Manishearth]

We now track the edition of each span.

oh, my.

[nikomatsakis]

Hmm, I'm not sure this is behaving right in some of the corner cases. I'll come back to it in a bit. But for example, when I add a macro to the Rust 2015 helper like this:

#[macro_export]
macro_rules! print_me {
    ($p:path) => {
        {
            use $p as V;
            println!("{}", V);
        }
    }
}

I expect the paths supplied to the macro from the Rust 2018 crate to use Rust 2018 semantics. I'm not 100% sure if they are or not yet :p I have to dig into the output a bit deeper.

[nikomatsakis]

(Obviously once you start concatenating paths and things it becomes less clear what is right -- I wanted to add some tests where we build paths like $a :: $b (where those are idents) as well -- it may be that we should be using the span of the use or something to decide, though in my example above it feels like we want the span of the path as a whole.)

[alexcrichton]

🗻

[rust-highfive]

The job x86_64-gnu-llvm-3.9 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.

[00:43:26] ....................................................................................................
[00:43:31] ...........................................................................i........................
[00:43:36] ....................................................i...............................................
[00:43:40] ........................................................................ii..........................
[00:43:45] ....F.F.............................................................................................
[00:43:53] iiiii...................................................
[00:43:53] failures:
[00:43:53] 
[00:43:53] 
[00:43:53] ---- [ui] ui/rust-2018/inject-2015-use-root-module-path.rs stdout ----
[00:43:53] normalized stderr:
[00:43:53] thread 'main' panicked at 'Some tests failed', tools/compiletest/src/main.rs:498:22
[00:43:53] error[E0432]: unresolved import `x::y`
[00:43:53]   --> $DIR/inject-2015-use-root-module-path.rs:28:5
[00:43:53]    |
[00:43:53] LL |     print_me!(x::y); //~ ERROR unresolved import `x::y`
[00:43:53]    |     ^^^^^^^^^^^^^^^^ no `y` in `x`
[00:43:53]    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
[00:43:53] 
[00:43:53] error: aborting due to previous error
[00:43:53] 
[00:43:53] 
[00:43:53] For more information about this error, try `rustc --explain E0432`.
[00:43:53] 
[00:43:53] 
[00:43:53] 
[00:43:53] The actual stderr differed from the expected stderr.
[00:43:53] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rust-2018/inject-2015-use-root-module-path/inject-2015-use-root-module-path.stderr
[00:43:53] To update references, rerun the tests and pass the `--bless` flag
[00:43:53] To only update this specific test, also pass `--test-args rust-2018/inject-2015-use-root-module-path.rs`
[00:43:53] error: 1 errors occurred comparing output.
[00:43:53] status: exit code: 101
[00:43:53] status: exit code: 101
[00:43:53] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/rust-2018/inject-2015-use-root-module-path.rs" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rust-2018/inject-2015-use-root-module-path/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--edition" "2018" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rust-2018/inject-2015-use-root-module-path/auxiliary" "-A" "unused"
[00:43:53] ------------------------------------------
[00:43:53] 
[00:43:53] ------------------------------------------
[00:43:53] stderr:
[00:43:53] stderr:
[00:43:53] ------------------------------------------
[00:43:53] {"message":"unresolved import `x::y`","code":{"code":"E0432","explanation":"\nAn import was unresolved.\n\nErroneous code example:\n\n```compile_fail,E0432\nuse something::Foo; // error: unresolved import `something::Foo`.\n```\n\nPaths in `use` statements are relative to the crate root. To import items\nrelative to the current and parent modules, use the `self::` and `super::`\nprefixes, respectively. Also verify that you didn't misspell the import\nname and that the import exists in the module from where you tried to\nimport it. Example:\n\n```\nuse self::something::Foo; // ok!\n\nmod something {\n    pub struct Foo;\n}\n# fn main() {}\n```\n\nOr, if you tried to use a module from an external crate, you may have missed\nthe `extern crate` declaration (which is usually placed in the crate root):\n\n```\nextern crate core; // Required to use the `core` crate\n\nuse core::any;\n# fn main() {}\n```\n"},"level":"error","spans":[{"file_name":"<print_me macros>","byte_start":26,"byte_end":34,"line_start":1,"line_end":1,"column_start":27,"column_end":35,"is_primary":true,"text":[{"text":"( $ p : path ) => { { use $ p as V ; println ! ( \"{}\" , V ) ; } }","highlight_start":27,"highlight_end":35}],"label":"no `y` in `x`","suggested_replacement":null,"suggestion_applicability":null,"expansion":{"span":{"file_name":"/checkout/src/test/ui/rust-2018/inject-2015-use-root-module-path.rs","byte_start":1024,"byte_end":1040,"line_start":28,"line_end":28,"column_start":5,"column_end":21,"is_primary":false,"text":[{"text":"    print_me!(x::y); //~ ERROR unresolved import `x::y`","highlight_start":5,"highlight_end":21}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null},"macro_decl_name":"print_me!","def_site_span":{"file_name":"<print_me macros>","byte_start":0,"byte_end":65,"line_start":1,"line_end":1,"column_start":1,"column_end":66,"is_primary":false,"text":[{"text":"( $ p : path ) => { { use $ p as V ; println ! ( \"{}\" , V ) ; } }","highlight_start":1,"highlight_end":66}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}}}],"children":[],"rendered":"error[E0432]: unresolved import `x::y`\n  --> /checkout/src/test/ui/rust-2018/inject-2015-use-root-module-path.rs:28:5\n   |\nLL |     print_me!(x::y); //~ ERROR unresolved import `x::y`\n   |     ^^^^^^^^^^^^^^^^ no `y` in `x`\n   |\n   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)\n\n"}
[00:43:53] {"message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error\n\n"}
[00:43:53] {"message":"For more information about this error, try `rustc --explain E0432`.","code":null,"level":"","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0432`.\n"}
[00:43:53] ------------------------------------------
[00:43:53] 
[00:43:53] 
[00:43:53] thread '[ui] ui/rust-2018/inject-2015-use-root-module-path.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:3044:9
[00:43:53] 
[00:43:53] 
[00:43:53] ---- [ui] ui/rust-2018/inject-2015-use-root-module.rs stdout ----
[00:43:53] 
[00:43:53] error: test compilation failed although it shouldn't!
[00:43:53] status: exit code: 101
[00:43:53] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/rust-2018/inject-2015-use-root-module.rs" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rust-2018/inject-2015-use-root-module/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--edition" "2018" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rust-2018/inject-2015-use-root-module/auxiliary" "-A" "unused"
[00:43:53] ------------------------------------------
[00:43:53] 
[00:43:53] ------------------------------------------
[00:43:53] stderr:
[00:43:53] stderr:
[00:43:53] ------------------------------------------
[00:43:53] {"message":"unresolved import `crate::x::y`","code":{"code":"E0432","explanation":"\nAn import was unresolved.\n\nErroneous code example:\n\n```compile_fail,E0432\nuse something::Foo; // error: unresolved import `something::Foo`.\n```\n\nPaths in `use` statements are relative to the crate root. To import items\nrelative to the current and parent modules, use the `self::` and `super::`\nprefixes, respectively. Also verify that you didn't misspell the import\nname and that the import exists in the module from where you tried to\nimport it. Example:\n\n```\nuse self::something::Foo; // ok!\n\nmod something {\n    pub struct Foo;\n}\n# fn main() {}\n```\n\nOr, if you tried to use a module from an external crate, you may have missed\nthe `extern crate` declaration (which is usually placed in the crate root):\n\n```\nextern crate core; // Required to use the `core` crate\n\nuse core::any;\n# fn main() {}\n```\n"},"level":"error","spans":[{"file_name":"<print_me macros>","byte_start":26,"byte_end":34,"line_start":1,"line_end":1,"column_start":27,"column_end":35,"is_primary":true,"text":[{"text":"( $ p : path ) => { { use $ p as V ; println ! ( \"{}\" , V ) ; } }","highlight_start":27,"highlight_end":35}],"label":"no `y` in `x`","suggested_replacement":null,"suggestion_applicability":null,"expansion":{"span":{"file_name":"/checkout/src/test/ui/rust-2018/inject-2015-use-root-module.rs","byte_start":960,"byte_end":983,"line_start":28,"line_end":28,"column_start":5,"column_end":28,"is_primary":false,"text":[{"text":"    print_me!(crate::x::y);","highlight_start":5,"highlight_end":28}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null},"macro_decl_name":"print_me!","def_site_span":{"file_name":"<print_me macros>","byte_start":0,"byte_end":65,"line_start":1,"line_end":1,"column_start":1,"column_end":66,"is_primary":false,"text":[{"text":"( $ p : path ) => { { use $ p as V ; println ! ( \"{}\" , V ) ; } }","highlight_start":1,"highlight_end":66}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}}}],"children":[],"rendered":"error[E0432]: unresolved import `crate::x::y`\n  --> /checkout/src/test/ui/rust-2018/inject-2015-use-root-module.rs:28:5\n   |\nLL |     print_me!(crate::x::y);\n   |     ^^^^^^^^^^^^^^^^^^^^^^^ no `y` in `x`\n   |\n   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)\n\n"}
[00:43:53] {"message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error\n\n"}
[00:43:53] {"message":"For more information about this error, try `rustc --explain E0432`.","code":null,"level":"","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0432`.\n"}
[00:43:53] ------------------------------------------
[00:43:53] 
[00:43:53] 
[00:43:53] thread '[ui] ui/rust-2018/inject-2015-use-root-module.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:3044:9
[00:43:53] 
[00:43:53] failures:
[00:43:53] failures:
[00:43:53]     [ui] ui/rust-2018/inject-2015-use-root-module-path.rs
[00:43:53]     [ui] ui/rust-2018/inject-2015-use-root-module.rs
[00:43:53] test result: FAILED. 1438 passed; 2 failed; 16 ignored; 0 measured; 0 filtered out
[00:43:53] 
[00:43:53] 
[00:43:53] 
[00:43:53] 
[00:43:53] 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-3.9/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" "3.9.1\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
[00:43:53] 
[00:43:53] 
[00:43:53] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[00:43:53] Build completed unsuccessfully in 0:02:25
[00:43:53] Build completed unsuccessfully in 0:02:25
[00:43:53] make: *** [check] Error 1
[00:43:53] Makefile:58: recipe for target 'check' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:0a7e6e2d
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

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)

[petrochenkov]

We can probably just implement Default for Edition.
"Local edition" needs to be kept in global data anyway because it's an "edition of SyntaxContext(0) aka not-a-macro-expansion" and it's set from default-default Edition2015 to self.opts.edition immediately after options are parsed.

[nikomatsakis]

Hmm. True, though I'm not wild about the fact that we rely so heavily on global / TLS data for this stuff.

[petrochenkov]

@nikomatsakis

I expect the paths supplied to the macro from the Rust 2018 crate to use Rust 2018 semantics.

Paths currently have spans from the "concatenation context" (see fn parse_path_common) just because they give better diagnostics.

In general, we can strictly rely only on spans of "atomic" tokens, for multi-token things like paths there are always multiple choices (#50122).
This is an important topic, and for imports it's especially important because we need to decide in what context the crate root will be resolved. See #50376 that's very similar to the problem you are trying to solve.

[bors]

☔️ The latest upstream changes (presumably #48309) made this pull request unmergeable. Please resolve the merge conflicts.

[nikomatsakis]

@petrochenkov

Sorry for the delay, got caught up in other things. I agree that #50122 and #50376 are intimately related. I'm not 100% sure I would even draw a distinction between them. I'll ponder a bit and try to leave a comment over there in those issues.

[alexcrichton]

I've written up a comment about a recent chat @nikomatsakis and I had where the conclusion was to basically punt on this PR for now. It's not clear whether this is the right strategy amongst alternatives, so we're going to not worry about solving this for the edition (as it doesn't seem all that pressing) and fix it if we uncover it later.

As a result, I'm removing the milestone from this PR.

[TimNN]

[...] where the conclusion was to basically punt on this PR for now.

Does this mean this PR can just be closed for now?

[alexcrichton]

Heh if I recall right @nikomatsakis felt bad closing the PR himself so I mentioned we can let normal triage processes close the PR. I'll perhaps preempt that slightly by closing it myself...

[nikomatsakis]

I'm of two minds because I do still want to see this reach some conclusion =) but keeping this PR open serves no real purpose.