90 lines
2.6 KiB
Rust
90 lines
2.6 KiB
Rust
//! lint when items are used after statements
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use clippy_utils::diagnostics::span_lint;
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use rustc_ast::ast::{Block, ItemKind, StmtKind};
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use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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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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/// ```rust
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/// // Bad
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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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/// ```rust
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/// // Good
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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 EarlyLintPass for ItemsAfterStatements {
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fn check_block(&mut self, cx: &EarlyContext<'_>, item: &Block) {
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if in_external_macro(cx.sess(), item.span) {
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return;
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}
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// skip initial items and trailing semicolons
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let stmts = item
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.stmts
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.iter()
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.map(|stmt| &stmt.kind)
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.skip_while(|s| matches!(**s, StmtKind::Item(..) | StmtKind::Empty));
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// lint on all further items
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for stmt in stmts {
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if let StmtKind::Item(ref it) = *stmt {
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if in_external_macro(cx.sess(), it.span) {
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return;
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}
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if let ItemKind::MacroDef(..) = it.kind {
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// do not lint `macro_rules`, but continue processing further statements
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continue;
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}
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span_lint(
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cx,
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ITEMS_AFTER_STATEMENTS,
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it.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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