diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/utils/internal_lints/if_chain_style.rs')
| -rw-r--r-- | src/tools/clippy/clippy_lints/src/utils/internal_lints/if_chain_style.rs | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/utils/internal_lints/if_chain_style.rs b/src/tools/clippy/clippy_lints/src/utils/internal_lints/if_chain_style.rs new file mode 100644 index 000000000..883a5c08e --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/utils/internal_lints/if_chain_style.rs @@ -0,0 +1,164 @@ +use clippy_utils::diagnostics::{span_lint, span_lint_and_then}; +use clippy_utils::{higher, is_else_clause, is_expn_of}; +use if_chain::if_chain; +use rustc_hir as hir; +use rustc_hir::{BinOpKind, Block, Expr, ExprKind, HirId, Local, Node, Stmt, StmtKind}; +use rustc_lint::{LateContext, LateLintPass, LintContext}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::{BytePos, Span}; + +declare_clippy_lint! { + /// Finds unidiomatic usage of `if_chain!` + pub IF_CHAIN_STYLE, + internal, + "non-idiomatic `if_chain!` usage" +} + +declare_lint_pass!(IfChainStyle => [IF_CHAIN_STYLE]); + +impl<'tcx> LateLintPass<'tcx> for IfChainStyle { + fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx hir::Block<'_>) { + let (local, after, if_chain_span) = if_chain! { + if let [Stmt { kind: StmtKind::Local(local), .. }, after @ ..] = block.stmts; + if let Some(if_chain_span) = is_expn_of(block.span, "if_chain"); + then { (local, after, if_chain_span) } else { return } + }; + if is_first_if_chain_expr(cx, block.hir_id, if_chain_span) { + span_lint( + cx, + IF_CHAIN_STYLE, + if_chain_local_span(cx, local, if_chain_span), + "`let` expression should be above the `if_chain!`", + ); + } else if local.span.ctxt() == block.span.ctxt() && is_if_chain_then(after, block.expr, if_chain_span) { + span_lint( + cx, + IF_CHAIN_STYLE, + if_chain_local_span(cx, local, if_chain_span), + "`let` expression should be inside `then { .. }`", + ); + } + } + + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { + let (cond, then, els) = if let Some(higher::IfOrIfLet { cond, r#else, then }) = higher::IfOrIfLet::hir(expr) { + (cond, then, r#else.is_some()) + } else { + return; + }; + let ExprKind::Block(then_block, _) = then.kind else { return }; + let if_chain_span = is_expn_of(expr.span, "if_chain"); + if !els { + check_nested_if_chains(cx, expr, then_block, if_chain_span); + } + let Some(if_chain_span) = if_chain_span else { return }; + // check for `if a && b;` + if_chain! { + if let ExprKind::Binary(op, _, _) = cond.kind; + if op.node == BinOpKind::And; + if cx.sess().source_map().is_multiline(cond.span); + then { + span_lint(cx, IF_CHAIN_STYLE, cond.span, "`if a && b;` should be `if a; if b;`"); + } + } + if is_first_if_chain_expr(cx, expr.hir_id, if_chain_span) + && is_if_chain_then(then_block.stmts, then_block.expr, if_chain_span) + { + span_lint(cx, IF_CHAIN_STYLE, expr.span, "`if_chain!` only has one `if`"); + } + } +} + +fn check_nested_if_chains( + cx: &LateContext<'_>, + if_expr: &Expr<'_>, + then_block: &Block<'_>, + if_chain_span: Option<Span>, +) { + #[rustfmt::skip] + let (head, tail) = match *then_block { + Block { stmts, expr: Some(tail), .. } => (stmts, tail), + Block { + stmts: &[ + ref head @ .., + Stmt { kind: StmtKind::Expr(tail) | StmtKind::Semi(tail), .. } + ], + .. + } => (head, tail), + _ => return, + }; + if_chain! { + if let Some(higher::IfOrIfLet { r#else: None, .. }) = higher::IfOrIfLet::hir(tail); + let sm = cx.sess().source_map(); + if head + .iter() + .all(|stmt| matches!(stmt.kind, StmtKind::Local(..)) && !sm.is_multiline(stmt.span)); + if if_chain_span.is_some() || !is_else_clause(cx.tcx, if_expr); + then { + } else { + return; + } + } + let (span, msg) = match (if_chain_span, is_expn_of(tail.span, "if_chain")) { + (None, Some(_)) => (if_expr.span, "this `if` can be part of the inner `if_chain!`"), + (Some(_), None) => (tail.span, "this `if` can be part of the outer `if_chain!`"), + (Some(a), Some(b)) if a != b => (b, "this `if_chain!` can be merged with the outer `if_chain!`"), + _ => return, + }; + span_lint_and_then(cx, IF_CHAIN_STYLE, span, msg, |diag| { + let (span, msg) = match head { + [] => return, + [stmt] => (stmt.span, "this `let` statement can also be in the `if_chain!`"), + [a, .., b] => ( + a.span.to(b.span), + "these `let` statements can also be in the `if_chain!`", + ), + }; + diag.span_help(span, msg); + }); +} + +fn is_first_if_chain_expr(cx: &LateContext<'_>, hir_id: HirId, if_chain_span: Span) -> bool { + cx.tcx + .hir() + .parent_iter(hir_id) + .find(|(_, node)| { + #[rustfmt::skip] + !matches!(node, Node::Expr(Expr { kind: ExprKind::Block(..), .. }) | Node::Stmt(_)) + }) + .map_or(false, |(id, _)| { + is_expn_of(cx.tcx.hir().span(id), "if_chain") != Some(if_chain_span) + }) +} + +/// Checks a trailing slice of statements and expression of a `Block` to see if they are part +/// of the `then {..}` portion of an `if_chain!` +fn is_if_chain_then(stmts: &[Stmt<'_>], expr: Option<&Expr<'_>>, if_chain_span: Span) -> bool { + let span = if let [stmt, ..] = stmts { + stmt.span + } else if let Some(expr) = expr { + expr.span + } else { + // empty `then {}` + return true; + }; + is_expn_of(span, "if_chain").map_or(true, |span| span != if_chain_span) +} + +/// Creates a `Span` for `let x = ..;` in an `if_chain!` call. +fn if_chain_local_span(cx: &LateContext<'_>, local: &Local<'_>, if_chain_span: Span) -> Span { + let mut span = local.pat.span; + if let Some(init) = local.init { + span = span.to(init.span); + } + span.adjust(if_chain_span.ctxt().outer_expn()); + let sm = cx.sess().source_map(); + let span = sm.span_extend_to_prev_str(span, "let", false, true).unwrap_or(span); + let span = sm.span_extend_to_next_char(span, ';', false); + Span::new( + span.lo() - BytePos(3), + span.hi() + BytePos(1), + span.ctxt(), + span.parent(), + ) +} |