Separate function bodies from their signatures in HIR #37918

flodiebold · Nov 21, 2016

Also give them their own dep map node.

I'm still unhappy with the handling of inlined items (1452edc), but maybe you have a suggestion how to improve it.

rust-highfive · Nov 21, 2016

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nikomatsakis (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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nikomatsakis · Nov 21, 2016

nikomatsakis requested changes Nov 21, 2016

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OK, this is looking really good! I had a few comments as to possible other ways that we could do things. I'm not sure which, if any, we should do before landing. I might have to experiment locally to form a real opinion in any case. Curious to get your opinion. These are the major themes I remember:

use a separate method for determining whether to visit bodies or not?
should we use DepNode::HirBody, or else give def-ids to fn bodies and use DepNode::Hir?
how to fix the collect edges? -- pushed some commits into the branch that fix it

I have some thoughts on the last one, but I think it'd be easier for me to just experiment locally and send you a diff if what I am saying makes sense. =)

nikomatsakis · Nov 21, 2016

src/librustc/hir/intravisit.rs

-impl<'v> Visitor<'v> for IdRangeComputingVisitor {
+impl<'a, 'ast> Visitor<'ast> for IdRangeComputingVisitor<'a, 'ast> {
+    fn nested_visit_map(&mut self) -> Option<(&Map<'ast>, NestedVisitMode)> {
+        Some((&self.map, NestedVisitMode::OnlyBodies))


Ah, of course... in our latest comments on the issue, I had forgotten the central problem where you want to visit fn bodies as the default, but of course we don't have the map by default... my inclination is to make the nested_body_map be a separate method, and make it have no default implementation, so that we always specify it for every visitor. I feel like it is potentially much more surprising to skip over bodies.

(Plus then we can avoid the NestedVisitMode tuple)

nikomatsakis · Nov 21, 2016

src/librustc/hir/map/blocks.rs

        self.handle(|i: ItemFnParts<'a>|  i.body,
                    |_, _, _: &'a ast::MethodSig, _, body: ast::ExprId, _, _|  body,
                    |c: ClosureParts<'a>| c.body)
    }

    pub fn decl(self) -> &'a FnDecl {
+        if let map::NodeInlinedItem(&InlinedItem { kind: InlinedItemKind::Fn(ref decl), .. }) = self.node {
+            return &decl;
+        }
        self.handle(|i: ItemFnParts<'a>|  &*i.decl,


Seems like the most natural way to extend this code would be extend handle to cover this case, probably by adding a fourth closure callback (inlined-item).

nikomatsakis · Nov 21, 2016

src/librustc_passes/consts.rs

-                                      fn_like.body(),
-                                      fn_like.span(),
-                                      fn_like.id());
+            let qualif = match self.tcx.const_qualif_map.borrow_mut().entry(fn_like.body().node_id()) {


What is happening here? Is this populated for inlined items or something? At minimum, some comments seem good.

Ah, yeah. Because the FnLike interface is only half implemented for inlined items, the fn_like call would fail for them, but the const_qualif_map is already populated for them, so I added the check beforehand. I'll need to clean that up somehow...

nikomatsakis · Nov 21, 2016

src/librustc/middle/cstore.rs

-    Item(DefId /* def-id in source crate */, P<hir::Item>),
-    TraitItem(DefId /* impl id */, P<hir::TraitItem>),
-    ImplItem(DefId /* impl id */, P<hir::ImplItem>)
+pub struct InlinedItem {


It's hard for me to assess if this is the best way -- vs say trying to encode the fn bodies separately. Apart from some nits (which I tried to cite), it does seem a bit cleaner than what was here before, though. Perhaps @eddyb has an opinion. But overall I think I like it?

Seems okay - shouldn't need the type of a constant though, in fact, you should be able to only record a Vec<DefId> for the arguments of a const fn, which doesn't even need to be in a separate enum anymore, just replace the kind field with const_fn_args: Vec<DefId> and that should be that.

That would make implementing FnLike even harder, though, I think.

You shouldn't need to implement FnLike though.

lookup_const_fn_by_id returns an FnLikeNode currently. But I guess it could return something else, e.g. a new enum?

Yeah, that would make more sense, FnLikeNode is more about pretty-printing.

nikomatsakis · Nov 21, 2016

src/librustc/dep_graph/dep_node.rs

@@ -42,6 +42,9 @@ pub enum DepNode<D: Clone + Debug> {
    // Represents the HIR node with the given node-id
    Hir(D),

+    // Represents the body of a function or method
+    HirBody(D),


This comment should specify that D is the def-id of the fn/method, as opposed to the id of the body itself.

As an alternative, we could get rid of this variant and give expression bodies their own def-id. Not yet sure which approach I prefer, have to read more.

nikomatsakis · Nov 21, 2016

src/test/incremental/hello_world.rs

@@ -31,7 +31,7 @@ mod x {
 mod y {
    use x;

-    #[rustc_dirty(label="TypeckItemBody", cfg="rpass2")]
+    #[rustc_clean(label="TypeckItemBody", cfg="rpass2")]


nikomatsakis · Nov 21, 2016

src/test/incremental/source_loc_macros.rs

 fn col_same() {
    let _ = column!();
 }

-#[rustc_clean(label="Hir", cfg="rpass2")]
+#[rustc_clean(label="HirBody", cfg="rpass2")]


Seems like it'd be good to have both Hir and HirBody here?

nikomatsakis · Nov 21, 2016

src/librustc/middle/cstore.rs

@@ -144,6 +144,7 @@ impl<'a> InlinedItemRef<'a> {
    pub fn from_trait_item(def_id: DefId, item: &'a hir::TraitItem, _map: &hir_map::Map) -> InlinedItemRef<'a> {
        let (body, kind) = match item.node {
            hir::ConstTraitItem(ref ty, Some(ref body)) => (&**body, InlinedItemKindRef::Const(ty)),
+            hir::ConstTraitItem(_, None) => bug!("InlinedItemRef::from_trait_item called for const without body"),


Is this a pre-existing bug, or something you introduced?

The code which calls from_trait_item takes care to only call it when there's a body, but I accidentally changed that once, and it wasn't immediately clear to me what I'd done wrong, so I just added this special message in case it happens again.

nikomatsakis · Nov 21, 2016

src/librustc_typeck/collect.rs

-    fn visit_item(&mut self, item: &hir::Item) {
+impl<'a, 'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'a, 'tcx> {
+    fn nested_visit_map(&mut self) -> Option<(&hir::map::Map<'tcx>, NestedVisitMode)> {
+        Some((&self.ccx.tcx.map, NestedVisitMode::OnlyBodies))


Hmm, this is suboptimal from the POV of the dep-graph tasks. We don't want the task which writes to the signature of a fn also reading from the fn body. Not sure what's the best way to tweak that just now; it's certainly possible.

nikomatsakis · Nov 21, 2016

src/test/incremental/hello_world.rs

-    #[rustc_clean(label="TypeckItemBody", cfg="rpass2")]
-    pub fn y() {
-        x::x();
+    // FIXME: This should be clean


I think the problem is the issue of collect reading from the fn body that I pointed out earlier.

flodiebold · Nov 21, 2016

Giving def-ids to bodies didn't really occur to me (I was thinking only definitions can have def-ids). That would probably make a few things cleaner, but I don't really have the perspective to know what else it may complicate. Also, how would the testing attributes work? Can you give attributes to expressions?

nikomatsakis · Nov 21, 2016

@flodiebold so I pushed two commits into your branch -- take a look. The first one fixes the TypeckCollect dependency problem in a reasonable clean way. The other one is a WIP -- basically a bunch of the "svh" tests are now much cleaner (in particular, a lot of once-dirty metadata and signatures are now clean) and I didn't get time to make them all pass.

nikomatsakis · Nov 21, 2016

Can you give attributes to expressions?

You can give attributes to statements, not expressions. So that is a possible complication; I guess we could look for an attribute on the first statement of a block or something.

nikomatsakis · Nov 21, 2016

@flodiebold all in all, the main thing I'd prefer to settle now is the visitor trait -- i.e., whether to have another method. The DepNode::HirBody thing is relatively easy to refactor later, I think.

bors · Nov 22, 2016

☔️ The latest upstream changes (presumably #37642) made this pull request unmergeable. Please resolve the merge conflicts.

flodiebold · Nov 22, 2016

@nikomatsakis It does seem to me like having two methods and having no default for nested_visit_map would be cleaner. I'll do that.

I'll fix the remaining tests; I think they may have come in during my last rebase, after which I forgot to check them again :)

nikomatsakis · Nov 22, 2016

@flodiebold

It does seem to me like having two methods and having no default for nested_visit_map would be cleaner. I'll do that.

Great =)

If that change is made and tests are working, I think this PR is ready to go. We can revisit the HirBody thing afterwards. I tend to think it'd be mildly cleaner to just have one variant (Hir) but I think the diff will be non-trivial-enough we might as well handle it in a follow-up (we have to create def-ids for fn bodies, at minimum? I feel like when I thought it through I decided there would be some (minor, but still) complications to overcome.)

flodiebold · Nov 24, 2016

@eddyb I refactored the inlined item handling again. I didn't get rid of the FnLikeNode usage for local const fns though, just for the inlined items.

@nikomatsakis Ok, I think I've addressed everything.

flodiebold · Nov 24, 2016

@michaelwoerister By the way, the unary_and_binary_exprs test was actually not working correctly because cfail2 was misspelled cfails2 in the rustc_clean annotations. Maybe that could be prevented somehow?

michaelwoerister · Nov 25, 2016

@flodiebold Good catch. Yes, maybe we can let the rest runner do some checks to prevent this.

bors · Nov 28, 2016

☔️ The latest upstream changes (presumably #37676) made this pull request unmergeable. Please resolve the merge conflicts.

eddyb · Nov 28, 2016

@flodiebold The commit "Merge master into separate-bodies" is worrying me - did you git pull without --rebase? In other news, I'm blocked on this PR, more or less, so let me know if I can help.

flodiebold · Nov 28, 2016

@eddyb I did merge because I wasn't sure whether a merge or a rebase is the preferred way to resolve conflicts. But I've actually just done a rebase onto the current master, so I could push that too.

Apart from that, I think the PR is ready and just needs to be looked at again.

eddyb · Nov 28, 2016

@flodiebold Rebase + force push is the way, only @bors does merges (into the auto branch).
I've also used merge locally to temporarily create a branch made from multiple PRs to test something.

flodiebold · Nov 28, 2016

Ok, that's what I preferred anyway. Rebased version coming up.

nikomatsakis · Nov 28, 2016

@flodiebold I was experimenting with an alternative version of the visitor refactoring. I've just rebased it atop your rebase, once it builds I'll push it to your branch and you can tell me what you think. It's actually sort of closer to your original approach.

nikomatsakis · Nov 28, 2016

done.

nikomatsakis · Nov 28, 2016

Pushed one more commit updating the comments a bit.

nikomatsakis · Nov 28, 2016

nikomatsakis approved these changes Nov 28, 2016

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nikomatsakis · Nov 28, 2016

@flodiebold (if you are happy with my latest commit, then r=me on the PR)

flodiebold · Nov 28, 2016

Ah, that does seem nicer. Makes it easier to search for visitors which currently don't return a map, too. 👍

nikomatsakis · Nov 28, 2016

@bors r+

bors · Nov 28, 2016

📌 Commit f620072 has been approved by nikomatsakis

eddyb · Nov 28, 2016

@bors r- failed Travis (librustdoc changes needed after rebase)

bors · Nov 29, 2016

☔️ The latest upstream changes (presumably #37791) made this pull request unmergeable. Please resolve the merge conflicts.

flodiebold · Nov 29, 2016

@eddyb @nikomatsakis Fixed and rebased :)

michaelwoerister · Nov 29, 2016

@bors r=nikomatsakis

bors · Nov 29, 2016

📌 Commit 593b273 has been approved by nikomatsakis

bors · Nov 29, 2016

⌛️ Testing commit 593b273 with merge f50dbd5...

nikomatsakis · Nov 29, 2016

@flodiebold great, thanks!

bors · Nov 29, 2016

rust-highfive assigned nikomatsakis Nov 21, 2016

flodiebold force-pushed the flodiebold:separate-bodies branch from cd9e807 to 5162288 Nov 28, 2016

Add exprs map to crate, collect item blocks there

069a244

flodiebold force-pushed the flodiebold:separate-bodies branch from f620072 to bc9bae9 Nov 29, 2016

librustdoc: Fix compilation after visitor change

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593b273

flodiebold force-pushed the flodiebold:separate-bodies branch from bc9bae9 to 593b273 Nov 29, 2016

bors merged commit 593b273 into rust-lang:master Nov 29, 2016
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This was referenced Nov 29, 2016

Merged

in region, treat current (and future) item-likes alike #37920

Merged

Warn unused type aliases, reimplemented #38051

This was referenced Dec 4, 2016

Merged

WIP: rustup rust-lang/rust-clippy#1373

Merged

annotate stricter lifetimes on LateLintPass methods to allow them to forward to a Visitor #38191

eddyb referenced this pull request Dec 18, 2016
Merged
[10/n] Split constants and functions' arguments into disjoint bodies. #38449

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Separate function bodies from their signatures in HIR #37918

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flodiebold commented Nov 21, 2016

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nikomatsakis and others added some commits Nov 21, 2016

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