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

// Previously this ICE'd because `fn g()` would be lowered, but the block associated with `fn f()`
// wasn't.

// compile-flags: --crate-type=lib

extern "C" {
    fn f() {
    //~^ incorrect function inside `extern` block
        fn g() {}
    }
}
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 2020-07-10 02:03:15 +00:00			// Previously this ICE'd because `fn g()` would be lowered, but the block associated with `fn f()`
			`// wasn't.`

			`// compile-flags: --crate-type=lib`

			`extern "C" {`
			`fn f() {`
			//~^ incorrect function inside `extern` block
			`fn g() {}`
			`}`
			`}`