87 lines
2.9 KiB
Rust
87 lines
2.9 KiB
Rust
use clippy_utils::diagnostics::span_lint_hir;
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use rustc_hir::{Block, ItemKind, StmtKind};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::declare_lint_pass;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for items declared after some statement in a block.
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///
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/// ### Why is this bad?
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/// Items live for the entire scope they are declared
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/// in. But statements are processed in order. This might cause confusion as
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/// it's hard to figure out which item is meant in a statement.
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///
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/// ### Example
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/// ```no_run
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/// fn foo() {
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/// println!("cake");
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/// }
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///
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/// fn main() {
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/// foo(); // prints "foo"
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/// fn foo() {
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/// println!("foo");
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/// }
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/// foo(); // prints "foo"
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/// }
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/// ```
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///
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/// Use instead:
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/// ```no_run
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/// fn foo() {
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/// println!("cake");
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/// }
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///
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/// fn main() {
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/// fn foo() {
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/// println!("foo");
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/// }
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/// foo(); // prints "foo"
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/// foo(); // prints "foo"
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/// }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub ITEMS_AFTER_STATEMENTS,
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pedantic,
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"blocks where an item comes after a statement"
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}
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declare_lint_pass!(ItemsAfterStatements => [ITEMS_AFTER_STATEMENTS]);
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impl LateLintPass<'_> for ItemsAfterStatements {
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fn check_block(&mut self, cx: &LateContext<'_>, block: &Block<'_>) {
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if block.stmts.len() > 1 {
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let ctxt = block.span.ctxt();
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let mut in_external = None;
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block
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.stmts
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.iter()
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.skip_while(|stmt| matches!(stmt.kind, StmtKind::Item(..)))
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.filter_map(|stmt| match stmt.kind {
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StmtKind::Item(id) => Some(cx.tcx.hir().item(id)),
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_ => None,
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})
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// Ignore macros since they can only see previously defined locals.
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.filter(|item| !matches!(item.kind, ItemKind::Macro(..)))
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// Stop linting if macros define items.
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.take_while(|item| item.span.ctxt() == ctxt)
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// Don't use `next` due to the complex filter chain.
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.for_each(|item| {
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// Only do the macro check once, but delay it until it's needed.
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if !*in_external.get_or_insert_with(|| in_external_macro(cx.sess(), block.span)) {
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span_lint_hir(
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cx,
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ITEMS_AFTER_STATEMENTS,
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item.hir_id(),
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item.span,
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"adding items after statements is confusing, since items exist from the \
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start of the scope",
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);
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}
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});
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}
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}
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}
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