rust/tests/ui/foreign/issue-74120-lowering-of-ffi-block-bodies.stderr

error: incorrect function inside `extern` block
  --> $DIR/issue-74120-lowering-of-ffi-block-bodies.rs:7:8
   |
LL |   extern "C" {
   |   ---------- `extern` blocks define existing foreign functions and functions inside of them cannot have a body
LL |       fn f() {
   |  ________^___-
   | |        |
   | |        cannot have a body
LL | |
LL | |         fn g() {}
LL | |     }
   | |_____- help: remove the invalid body: `;`
   |
   = 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
   = note: for more information, visit https://doc.rust-lang.org/std/keyword.extern.html

error: aborting due to previous error
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 #74120 2020-07-09 21:03:15 -05:00			error: incorrect function inside `extern` block
			`--> $DIR/issue-74120-lowering-of-ffi-block-bodies.rs:7:8`
			`\|`
			`LL \| extern "C" {`
			\| ---------- `extern` blocks define existing foreign functions and functions inside of them cannot have a body
			`LL \| fn f() {`
			`\| ________^___-`
			`\| \| \|`
			`\| \| cannot have a body`
			`LL \| \|`
			`LL \| \| fn g() {}`
			`LL \| \| }`
			\| \|_____- help: remove the invalid body: `;`
			`\|`
			= 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
			`= note: for more information, visit https://doc.rust-lang.org/std/keyword.extern.html`

			`error: aborting due to previous error`