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Rollup merge of rust-lang#74204 - ayazhafiz:i/74120, r=eddyb
Don't visit foreign function bodies when lowering ast to hir Previously the existence of bodies inside a foreign function block would cause a panic in the hir `NodeCollector` during its collection of crate bodies to compute a crate hash: https://github.com/rust-lang/rust/blob/e59b08e62ea691916d2f063cac5aab4634128022/src/librustc_middle/hir/map/collector.rs#L154-L158 The collector walks the hir tree and creates a map of hir nodes, then attaching bodies in the crate to their owner in the map. For a code like ```rust extern "C" { fn f() { fn g() {} } } ``` The crate bodies include the body of the function `g`. But foreign functions cannot have bodies, and while the parser AST permits a foreign function to have a body, the hir doesn't. This means that the body of `f` is not present in the hir, and so neither is `g`. So when the `NodeCollector` finishes the walking the hir, it has no record of `g`, cannot find an owner for the body of `g` it sees in the crate bodies, and blows up. Why do the crate bodies include the body of `g`? The AST walker has a need a for walking function bodies, and FFIs share the same AST node as functions in other contexts. There are at least two options to fix this: - Don't unwrap the map entry for an hir node in the `NodeCollector` - Modifier the ast->hir lowering visitor to ignore foreign function blocks I don't think the first is preferrable, since we want to know when we can't find a body for an hir node that we thought had one (dropping this information may lead to an invalid hash). So this commit implements the second option. Closes rust-lang#74120
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src/librustc_ast_lowering/item.rs

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@@ -5,7 +5,7 @@ use crate::Arena;
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use rustc_ast::ast::*;
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use rustc_ast::node_id::NodeMap;
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use rustc_ast::ptr::P;
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use rustc_ast::visit::{self, AssocCtxt, Visitor};
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use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
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use rustc_data_structures::fx::FxHashSet;
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use rustc_errors::struct_span_err;
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use rustc_hir as hir;
@@ -75,6 +75,18 @@ impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
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}
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}
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fn visit_fn(&mut self, fk: FnKind<'a>, sp: Span, _: NodeId) {
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match fk {
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FnKind::Fn(FnCtxt::Foreign, _, sig, _, _) => {
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self.visit_fn_header(&sig.header);
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visit::walk_fn_decl(self, &sig.decl);
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// Don't visit the foreign function body even if it has one, since lowering the
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// body would have no meaning and will have already been caught as a parse error.
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}
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_ => visit::walk_fn(self, fk, sp),
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}
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}
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fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) {
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self.lctx.with_hir_id_owner(item.id, |lctx| match ctxt {
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AssocCtxt::Trait => {
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// Previously this ICE'd because `fn g()` would be lowered, but the block associated with `fn f()`
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// wasn't.
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// compile-flags: --crate-type=lib
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extern "C" {
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fn f() {
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//~^ incorrect function inside `extern` block
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fn g() {}
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}
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}
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error: incorrect function inside `extern` block
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--> $DIR/issue-74120-lowering-of-ffi-block-bodies.rs:7:8
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|
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LL | extern "C" {
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| ---------- `extern` blocks define existing foreign functions and functions inside of them cannot have a body
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LL | fn f() {
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| ________^___-
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| | |
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| | cannot have a body
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LL | |
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LL | | fn g() {}
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LL | | }
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| |_____- help: remove the invalid body: `;`
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|
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= help: you might have meant to write a function accessible through FFI, which can be done by writing `extern fn` outside of the `extern` block
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= note: for more information, visit https://doc.rust-lang.org/std/keyword.extern.html
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error: aborting due to previous error
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