-use crate::utils::{eq_expr_value, in_macro, search_same, SpanlessEq, SpanlessHash};
-use crate::utils::{get_parent_expr, if_sequence, span_lint_and_note};
-use rustc_hir::{Block, Expr, ExprKind};
+use clippy_utils::diagnostics::{span_lint_and_note, span_lint_and_then};
+use clippy_utils::source::{first_line_of_span, indent_of, reindent_multiline, snippet, snippet_opt};
+use clippy_utils::{
+ both, count_eq, eq_expr_value, get_enclosing_block, get_parent_expr, if_sequence, in_macro, is_else_clause,
+ is_lint_allowed, search_same, ContainsName, SpanlessEq, SpanlessHash,
+};
+use if_chain::if_chain;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{Applicability, DiagnosticBuilder};
+use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc_hir::{Block, Expr, ExprKind, HirId};
use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::hir::map::Map;
use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::{source_map::Span, symbol::Symbol, BytePos};
+use std::borrow::Cow;
declare_clippy_lint! {
/// **What it does:** Checks for consecutive `if`s with the same condition.
"`if` with the same `then` and `else` blocks"
}
-declare_lint_pass!(CopyAndPaste => [IFS_SAME_COND, SAME_FUNCTIONS_IN_IF_CONDITION, IF_SAME_THEN_ELSE]);
+declare_clippy_lint! {
+ /// **What it does:** Checks if the `if` and `else` block contain shared code that can be
+ /// moved out of the blocks.
+ ///
+ /// **Why is this bad?** Duplicate code is less maintainable.
+ ///
+ /// **Known problems:**
+ /// * The lint doesn't check if the moved expressions modify values that are beeing used in
+ /// the if condition. The suggestion can in that case modify the behavior of the program.
+ /// See [rust-clippy#7452](https://github.com/rust-lang/rust-clippy/issues/7452)
+ ///
+ /// **Example:**
+ /// ```ignore
+ /// let foo = if … {
+ /// println!("Hello World");
+ /// 13
+ /// } else {
+ /// println!("Hello World");
+ /// 42
+ /// };
+ /// ```
+ ///
+ /// Could be written as:
+ /// ```ignore
+ /// println!("Hello World");
+ /// let foo = if … {
+ /// 13
+ /// } else {
+ /// 42
+ /// };
+ /// ```
+ pub BRANCHES_SHARING_CODE,
+ complexity,
+ "`if` statement with shared code in all blocks"
+}
+
+declare_lint_pass!(CopyAndPaste => [
+ IFS_SAME_COND,
+ SAME_FUNCTIONS_IN_IF_CONDITION,
+ IF_SAME_THEN_ELSE,
+ BRANCHES_SHARING_CODE
+]);
impl<'tcx> LateLintPass<'tcx> for CopyAndPaste {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if !expr.span.from_expansion() {
- // skip ifs directly in else, it will be checked in the parent if
- if let Some(&Expr {
- kind: ExprKind::If(_, _, Some(ref else_expr)),
- ..
- }) = get_parent_expr(cx, expr)
- {
- if else_expr.hir_id == expr.hir_id {
- return;
+ if let ExprKind::If(_, _, _) = expr.kind {
+ // skip ifs directly in else, it will be checked in the parent if
+ if let Some(&Expr {
+ kind: ExprKind::If(_, _, Some(else_expr)),
+ ..
+ }) = get_parent_expr(cx, expr)
+ {
+ if else_expr.hir_id == expr.hir_id {
+ return;
+ }
+ }
+
+ let (conds, blocks) = if_sequence(expr);
+ // Conditions
+ lint_same_cond(cx, &conds);
+ lint_same_fns_in_if_cond(cx, &conds);
+ // Block duplication
+ lint_same_then_else(cx, &blocks, conds.len() == blocks.len(), expr);
+ }
+ }
+ }
+}
+
+/// Implementation of `BRANCHES_SHARING_CODE` and `IF_SAME_THEN_ELSE` if the blocks are equal.
+fn lint_same_then_else<'tcx>(
+ cx: &LateContext<'tcx>,
+ blocks: &[&Block<'tcx>],
+ has_conditional_else: bool,
+ expr: &'tcx Expr<'_>,
+) {
+ // We only lint ifs with multiple blocks
+ if blocks.len() < 2 || is_else_clause(cx.tcx, expr) {
+ return;
+ }
+
+ // Check if each block has shared code
+ let has_expr = blocks[0].expr.is_some();
+
+ let (start_eq, mut end_eq, expr_eq) = if let Some(block_eq) = scan_block_for_eq(cx, blocks) {
+ (block_eq.start_eq, block_eq.end_eq, block_eq.expr_eq)
+ } else {
+ return;
+ };
+
+ // BRANCHES_SHARING_CODE prerequisites
+ if has_conditional_else || (start_eq == 0 && end_eq == 0 && (has_expr && !expr_eq)) {
+ return;
+ }
+
+ // Only the start is the same
+ if start_eq != 0 && end_eq == 0 && (!has_expr || !expr_eq) {
+ let block = blocks[0];
+ let start_stmts = block.stmts.split_at(start_eq).0;
+
+ let mut start_walker = UsedValueFinderVisitor::new(cx);
+ for stmt in start_stmts {
+ intravisit::walk_stmt(&mut start_walker, stmt);
+ }
+
+ emit_branches_sharing_code_lint(
+ cx,
+ start_eq,
+ 0,
+ false,
+ check_for_warn_of_moved_symbol(cx, &start_walker.def_symbols, expr),
+ blocks,
+ expr,
+ );
+ } else if end_eq != 0 || (has_expr && expr_eq) {
+ let block = blocks[blocks.len() - 1];
+ let (start_stmts, block_stmts) = block.stmts.split_at(start_eq);
+ let (block_stmts, end_stmts) = block_stmts.split_at(block_stmts.len() - end_eq);
+
+ // Scan start
+ let mut start_walker = UsedValueFinderVisitor::new(cx);
+ for stmt in start_stmts {
+ intravisit::walk_stmt(&mut start_walker, stmt);
+ }
+ let mut moved_syms = start_walker.def_symbols;
+
+ // Scan block
+ let mut block_walker = UsedValueFinderVisitor::new(cx);
+ for stmt in block_stmts {
+ intravisit::walk_stmt(&mut block_walker, stmt);
+ }
+ let mut block_defs = block_walker.defs;
+
+ // Scan moved stmts
+ let mut moved_start: Option<usize> = None;
+ let mut end_walker = UsedValueFinderVisitor::new(cx);
+ for (index, stmt) in end_stmts.iter().enumerate() {
+ intravisit::walk_stmt(&mut end_walker, stmt);
+
+ for value in &end_walker.uses {
+ // Well we can't move this and all prev statements. So reset
+ if block_defs.contains(value) {
+ moved_start = Some(index + 1);
+ end_walker.defs.drain().for_each(|x| {
+ block_defs.insert(x);
+ });
+
+ end_walker.def_symbols.clear();
}
}
- let (conds, blocks) = if_sequence(expr);
- lint_same_then_else(cx, &blocks);
- lint_same_cond(cx, &conds);
- lint_same_fns_in_if_cond(cx, &conds);
+ end_walker.uses.clear();
+ }
+
+ if let Some(moved_start) = moved_start {
+ end_eq -= moved_start;
+ }
+
+ let end_linable = block.expr.map_or_else(
+ || end_eq != 0,
+ |expr| {
+ intravisit::walk_expr(&mut end_walker, expr);
+ end_walker.uses.iter().any(|x| !block_defs.contains(x))
+ },
+ );
+
+ if end_linable {
+ end_walker.def_symbols.drain().for_each(|x| {
+ moved_syms.insert(x);
+ });
}
+
+ emit_branches_sharing_code_lint(
+ cx,
+ start_eq,
+ end_eq,
+ end_linable,
+ check_for_warn_of_moved_symbol(cx, &moved_syms, expr),
+ blocks,
+ expr,
+ );
}
}
-/// Implementation of `IF_SAME_THEN_ELSE`.
-fn lint_same_then_else(cx: &LateContext<'_>, blocks: &[&Block<'_>]) {
- let eq: &dyn Fn(&&Block<'_>, &&Block<'_>) -> bool =
- &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).eq_block(lhs, rhs) };
+struct BlockEqual {
+ /// The amount statements that are equal from the start
+ start_eq: usize,
+ /// The amount statements that are equal from the end
+ end_eq: usize,
+ /// An indication if the block expressions are the same. This will also be true if both are
+ /// `None`
+ expr_eq: bool,
+}
- if let Some((i, j)) = search_same_sequenced(blocks, eq) {
- span_lint_and_note(
+/// This function can also trigger the `IF_SAME_THEN_ELSE` in which case it'll return `None` to
+/// abort any further processing and avoid duplicate lint triggers.
+fn scan_block_for_eq(cx: &LateContext<'tcx>, blocks: &[&Block<'tcx>]) -> Option<BlockEqual> {
+ let mut start_eq = usize::MAX;
+ let mut end_eq = usize::MAX;
+ let mut expr_eq = true;
+ for win in blocks.windows(2) {
+ let l_stmts = win[0].stmts;
+ let r_stmts = win[1].stmts;
+
+ // `SpanlessEq` now keeps track of the locals and is therefore context sensitive clippy#6752.
+ // The comparison therefore needs to be done in a way that builds the correct context.
+ let mut evaluator = SpanlessEq::new(cx);
+ let mut evaluator = evaluator.inter_expr();
+
+ let current_start_eq = count_eq(&mut l_stmts.iter(), &mut r_stmts.iter(), |l, r| evaluator.eq_stmt(l, r));
+
+ let current_end_eq = {
+ // We skip the middle statements which can't be equal
+ let end_comparison_count = l_stmts.len().min(r_stmts.len()) - current_start_eq;
+ let it1 = l_stmts.iter().skip(l_stmts.len() - end_comparison_count);
+ let it2 = r_stmts.iter().skip(r_stmts.len() - end_comparison_count);
+ it1.zip(it2)
+ .fold(0, |acc, (l, r)| if evaluator.eq_stmt(l, r) { acc + 1 } else { 0 })
+ };
+ let block_expr_eq = both(&win[0].expr, &win[1].expr, |l, r| evaluator.eq_expr(l, r));
+
+ // IF_SAME_THEN_ELSE
+ if_chain! {
+ if block_expr_eq;
+ if l_stmts.len() == r_stmts.len();
+ if l_stmts.len() == current_start_eq;
+ if !is_lint_allowed(cx, IF_SAME_THEN_ELSE, win[0].hir_id);
+ if !is_lint_allowed(cx, IF_SAME_THEN_ELSE, win[1].hir_id);
+ then {
+ span_lint_and_note(
+ cx,
+ IF_SAME_THEN_ELSE,
+ win[0].span,
+ "this `if` has identical blocks",
+ Some(win[1].span),
+ "same as this",
+ );
+
+ return None;
+ }
+ }
+
+ start_eq = start_eq.min(current_start_eq);
+ end_eq = end_eq.min(current_end_eq);
+ expr_eq &= block_expr_eq;
+ }
+
+ if !expr_eq {
+ end_eq = 0;
+ }
+
+ // Check if the regions are overlapping. Set `end_eq` to prevent the overlap
+ let min_block_size = blocks.iter().map(|x| x.stmts.len()).min().unwrap();
+ if (start_eq + end_eq) > min_block_size {
+ end_eq = min_block_size - start_eq;
+ }
+
+ Some(BlockEqual {
+ start_eq,
+ end_eq,
+ expr_eq,
+ })
+}
+
+fn check_for_warn_of_moved_symbol(
+ cx: &LateContext<'tcx>,
+ symbols: &FxHashSet<Symbol>,
+ if_expr: &'tcx Expr<'_>,
+) -> bool {
+ get_enclosing_block(cx, if_expr.hir_id).map_or(false, |block| {
+ let ignore_span = block.span.shrink_to_lo().to(if_expr.span);
+
+ symbols
+ .iter()
+ .filter(|sym| !sym.as_str().starts_with('_'))
+ .any(move |sym| {
+ let mut walker = ContainsName {
+ name: *sym,
+ result: false,
+ };
+
+ // Scan block
+ block
+ .stmts
+ .iter()
+ .filter(|stmt| !ignore_span.overlaps(stmt.span))
+ .for_each(|stmt| intravisit::walk_stmt(&mut walker, stmt));
+
+ if let Some(expr) = block.expr {
+ intravisit::walk_expr(&mut walker, expr);
+ }
+
+ walker.result
+ })
+ })
+}
+
+fn emit_branches_sharing_code_lint(
+ cx: &LateContext<'tcx>,
+ start_stmts: usize,
+ end_stmts: usize,
+ lint_end: bool,
+ warn_about_moved_symbol: bool,
+ blocks: &[&Block<'tcx>],
+ if_expr: &'tcx Expr<'_>,
+) {
+ if start_stmts == 0 && !lint_end {
+ return;
+ }
+
+ // (help, span, suggestion)
+ let mut suggestions: Vec<(&str, Span, String)> = vec![];
+ let mut add_expr_note = false;
+
+ // Construct suggestions
+ if start_stmts > 0 {
+ let block = blocks[0];
+ let span_start = first_line_of_span(cx, if_expr.span).shrink_to_lo();
+ let span_end = block.stmts[start_stmts - 1].span.source_callsite();
+
+ let cond_span = first_line_of_span(cx, if_expr.span).until(block.span);
+ let cond_snippet = reindent_multiline(snippet(cx, cond_span, "_"), false, None);
+ let cond_indent = indent_of(cx, cond_span);
+ let moved_span = block.stmts[0].span.source_callsite().to(span_end);
+ let moved_snippet = reindent_multiline(snippet(cx, moved_span, "_"), true, None);
+ let suggestion = moved_snippet.to_string() + "\n" + &cond_snippet + "{";
+ let suggestion = reindent_multiline(Cow::Borrowed(&suggestion), true, cond_indent);
+
+ let span = span_start.to(span_end);
+ suggestions.push(("start", span, suggestion.to_string()));
+ }
+
+ if lint_end {
+ let block = blocks[blocks.len() - 1];
+ let span_end = block.span.shrink_to_hi();
+
+ let moved_start = if end_stmts == 0 && block.expr.is_some() {
+ block.expr.unwrap().span
+ } else {
+ block.stmts[block.stmts.len() - end_stmts].span
+ }
+ .source_callsite();
+ let moved_end = block
+ .expr
+ .map_or_else(|| block.stmts[block.stmts.len() - 1].span, |expr| expr.span)
+ .source_callsite();
+
+ let moved_span = moved_start.to(moved_end);
+ let moved_snipped = reindent_multiline(snippet(cx, moved_span, "_"), true, None);
+ let indent = indent_of(cx, if_expr.span.shrink_to_hi());
+ let suggestion = "}\n".to_string() + &moved_snipped;
+ let suggestion = reindent_multiline(Cow::Borrowed(&suggestion), true, indent);
+
+ let mut span = moved_start.to(span_end);
+ // Improve formatting if the inner block has indention (i.e. normal Rust formatting)
+ let test_span = Span::new(span.lo() - BytePos(4), span.lo(), span.ctxt());
+ if snippet_opt(cx, test_span)
+ .map(|snip| snip == " ")
+ .unwrap_or_default()
+ {
+ span = span.with_lo(test_span.lo());
+ }
+
+ suggestions.push(("end", span, suggestion.to_string()));
+ add_expr_note = !cx.typeck_results().expr_ty(if_expr).is_unit();
+ }
+
+ let add_optional_msgs = |diag: &mut DiagnosticBuilder<'_>| {
+ if add_expr_note {
+ diag.note("The end suggestion probably needs some adjustments to use the expression result correctly");
+ }
+
+ if warn_about_moved_symbol {
+ diag.warn("Some moved values might need to be renamed to avoid wrong references");
+ }
+ };
+
+ // Emit lint
+ if suggestions.len() == 1 {
+ let (place_str, span, sugg) = suggestions.pop().unwrap();
+ let msg = format!("all if blocks contain the same code at the {}", place_str);
+ let help = format!("consider moving the {} statements out like this", place_str);
+ span_lint_and_then(cx, BRANCHES_SHARING_CODE, span, msg.as_str(), |diag| {
+ diag.span_suggestion(span, help.as_str(), sugg, Applicability::Unspecified);
+
+ add_optional_msgs(diag);
+ });
+ } else if suggestions.len() == 2 {
+ let (_, end_span, end_sugg) = suggestions.pop().unwrap();
+ let (_, start_span, start_sugg) = suggestions.pop().unwrap();
+ span_lint_and_then(
cx,
- IF_SAME_THEN_ELSE,
- j.span,
- "this `if` has identical blocks",
- Some(i.span),
- "same as this",
+ BRANCHES_SHARING_CODE,
+ start_span,
+ "all if blocks contain the same code at the start and the end. Here at the start",
+ move |diag| {
+ diag.span_note(end_span, "and here at the end");
+
+ diag.span_suggestion(
+ start_span,
+ "consider moving the start statements out like this",
+ start_sugg,
+ Applicability::Unspecified,
+ );
+
+ diag.span_suggestion(
+ end_span,
+ "and consider moving the end statements out like this",
+ end_sugg,
+ Applicability::Unspecified,
+ );
+
+ add_optional_msgs(diag);
+ },
);
}
}
+/// This visitor collects `HirId`s and Symbols of defined symbols and `HirId`s of used values.
+struct UsedValueFinderVisitor<'a, 'tcx> {
+ cx: &'a LateContext<'tcx>,
+
+ /// The `HirId`s of defined values in the scanned statements
+ defs: FxHashSet<HirId>,
+
+ /// The Symbols of the defined symbols in the scanned statements
+ def_symbols: FxHashSet<Symbol>,
+
+ /// The `HirId`s of the used values
+ uses: FxHashSet<HirId>,
+}
+
+impl<'a, 'tcx> UsedValueFinderVisitor<'a, 'tcx> {
+ fn new(cx: &'a LateContext<'tcx>) -> Self {
+ UsedValueFinderVisitor {
+ cx,
+ defs: FxHashSet::default(),
+ def_symbols: FxHashSet::default(),
+ uses: FxHashSet::default(),
+ }
+ }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for UsedValueFinderVisitor<'a, 'tcx> {
+ type Map = Map<'tcx>;
+
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+ NestedVisitorMap::All(self.cx.tcx.hir())
+ }
+
+ fn visit_local(&mut self, l: &'tcx rustc_hir::Local<'tcx>) {
+ let local_id = l.pat.hir_id;
+ self.defs.insert(local_id);
+
+ if let Some(sym) = l.pat.simple_ident() {
+ self.def_symbols.insert(sym.name);
+ }
+
+ if let Some(expr) = l.init {
+ intravisit::walk_expr(self, expr);
+ }
+ }
+
+ fn visit_qpath(&mut self, qpath: &'tcx rustc_hir::QPath<'tcx>, id: HirId, _span: rustc_span::Span) {
+ if let rustc_hir::QPath::Resolved(_, path) = *qpath {
+ if path.segments.len() == 1 {
+ if let rustc_hir::def::Res::Local(var) = self.cx.qpath_res(qpath, id) {
+ self.uses.insert(var);
+ }
+ }
+ }
+ }
+}
+
/// Implementation of `IFS_SAME_COND`.
fn lint_same_cond(cx: &LateContext<'_>, conds: &[&Expr<'_>]) {
let hash: &dyn Fn(&&Expr<'_>) -> u64 = &|expr| -> u64 {
);
}
}
-
-fn search_same_sequenced<T, Eq>(exprs: &[T], eq: Eq) -> Option<(&T, &T)>
-where
- Eq: Fn(&T, &T) -> bool,
-{
- for win in exprs.windows(2) {
- if eq(&win[0], &win[1]) {
- return Some((&win[0], &win[1]));
- }
- }
- None
-}
projects / rust.git / blobdiff