//! calculate cognitive complexity and warn about overly complex functions
-use rustc::cfg::CFG;
-use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
-use rustc::hir::*;
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintContext, LintPass};
-use rustc::ty;
-use rustc::{declare_tool_lint, impl_lint_pass};
-use syntax::ast::Attribute;
-use syntax::source_map::Span;
+use rustc::hir::map::Map;
+use rustc_ast::ast::Attribute;
+use rustc_hir::intravisit::{walk_expr, FnKind, NestedVisitorMap, Visitor};
+use rustc_hir::{Body, Expr, ExprKind, FnDecl, HirId};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::source_map::Span;
+use rustc_span::BytePos;
-use crate::utils::{is_allowed, match_type, paths, span_help_and_lint, LimitStack};
+use crate::utils::{match_type, paths, snippet_opt, span_lint_and_help, LimitStack};
declare_clippy_lint! {
/// **What it does:** Checks for methods with high cognitive complexity.
}
impl CognitiveComplexity {
+ #[must_use]
pub fn new(limit: u64) -> Self {
Self {
limit: LimitStack::new(limit),
impl_lint_pass!(CognitiveComplexity => [COGNITIVE_COMPLEXITY]);
impl CognitiveComplexity {
- fn check<'a, 'tcx>(&mut self, cx: &'a LateContext<'a, 'tcx>, body: &'tcx Body, span: Span) {
- if span.from_expansion() {
+ #[allow(clippy::cast_possible_truncation)]
+ fn check<'a, 'tcx>(
+ &mut self,
+ cx: &'a LateContext<'a, 'tcx>,
+ kind: FnKind<'tcx>,
+ decl: &'tcx FnDecl<'_>,
+ body: &'tcx Body<'_>,
+ body_span: Span,
+ ) {
+ if body_span.from_expansion() {
return;
}
- let cfg = CFG::new(cx.tcx, body);
let expr = &body.value;
- let n = cfg.graph.len_nodes() as u64;
- let e = cfg.graph.len_edges() as u64;
- if e + 2 < n {
- // the function has unreachable code, other lints should catch this
- return;
- }
- let cc = e + 2 - n;
- let mut helper = CCHelper {
- match_arms: 0,
- divergence: 0,
- short_circuits: 0,
- returns: 0,
- cx,
- };
+
+ let mut helper = CCHelper { cc: 1, returns: 0 };
helper.visit_expr(expr);
- let CCHelper {
- match_arms,
- divergence,
- short_circuits,
- returns,
- ..
- } = helper;
+ let CCHelper { cc, returns } = helper;
let ret_ty = cx.tables.node_type(expr.hir_id);
let ret_adjust = if match_type(cx, ret_ty, &paths::RESULT) {
returns
(returns / 2)
};
- if cc + divergence < match_arms + short_circuits {
- report_cc_bug(
+ let mut rust_cc = cc;
+ // prevent degenerate cases where unreachable code contains `return` statements
+ if rust_cc >= ret_adjust {
+ rust_cc -= ret_adjust;
+ }
+
+ if rust_cc > self.limit.limit() {
+ let fn_span = match kind {
+ FnKind::ItemFn(ident, _, _, _, _) | FnKind::Method(ident, _, _, _) => ident.span,
+ FnKind::Closure(_) => {
+ let header_span = body_span.with_hi(decl.output.span().lo());
+ let pos = snippet_opt(cx, header_span).and_then(|snip| {
+ let low_offset = snip.find('|')?;
+ let high_offset = 1 + snip.get(low_offset + 1..)?.find('|')?;
+ let low = header_span.lo() + BytePos(low_offset as u32);
+ let high = low + BytePos(high_offset as u32 + 1);
+
+ Some((low, high))
+ });
+
+ if let Some((low, high)) = pos {
+ Span::new(low, high, header_span.ctxt())
+ } else {
+ return;
+ }
+ },
+ };
+
+ span_lint_and_help(
cx,
- cc,
- match_arms,
- divergence,
- short_circuits,
- ret_adjust,
- span,
- body.id().hir_id,
+ COGNITIVE_COMPLEXITY,
+ fn_span,
+ &format!(
+ "the function has a cognitive complexity of ({}/{})",
+ rust_cc,
+ self.limit.limit()
+ ),
+ "you could split it up into multiple smaller functions",
);
- } else {
- let mut rust_cc = cc + divergence - match_arms - short_circuits;
- // prevent degenerate cases where unreachable code contains `return` statements
- if rust_cc >= ret_adjust {
- rust_cc -= ret_adjust;
- }
- if rust_cc > self.limit.limit() {
- span_help_and_lint(
- cx,
- COGNITIVE_COMPLEXITY,
- span,
- &format!("the function has a cognitive complexity of {}", rust_cc),
- "you could split it up into multiple smaller functions",
- );
- }
}
}
}
fn check_fn(
&mut self,
cx: &LateContext<'a, 'tcx>,
- _: intravisit::FnKind<'tcx>,
- _: &'tcx FnDecl,
- body: &'tcx Body,
+ kind: FnKind<'tcx>,
+ decl: &'tcx FnDecl<'_>,
+ body: &'tcx Body<'_>,
span: Span,
hir_id: HirId,
) {
let def_id = cx.tcx.hir().local_def_id(hir_id);
if !cx.tcx.has_attr(def_id, sym!(test)) {
- self.check(cx, body, span);
+ self.check(cx, kind, decl, body, span);
}
}
}
}
-struct CCHelper<'a, 'tcx> {
- match_arms: u64,
- divergence: u64,
+struct CCHelper {
+ cc: u64,
returns: u64,
- short_circuits: u64, // && and ||
- cx: &'a LateContext<'a, 'tcx>,
}
-impl<'a, 'tcx> Visitor<'tcx> for CCHelper<'a, 'tcx> {
- fn visit_expr(&mut self, e: &'tcx Expr) {
- match e.node {
+impl<'tcx> Visitor<'tcx> for CCHelper {
+ type Map = Map<'tcx>;
+
+ fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
+ walk_expr(self, e);
+ match e.kind {
ExprKind::Match(_, ref arms, _) => {
- walk_expr(self, e);
- let arms_n: u64 = arms.iter().map(|arm| arm.pats.len() as u64).sum();
- if arms_n > 1 {
- self.match_arms += arms_n - 2;
- }
- },
- ExprKind::Call(ref callee, _) => {
- walk_expr(self, e);
- let ty = self.cx.tables.node_type(callee.hir_id);
- match ty.sty {
- ty::FnDef(..) | ty::FnPtr(_) => {
- let sig = ty.fn_sig(self.cx.tcx);
- if sig.skip_binder().output().sty == ty::Never {
- self.divergence += 1;
- }
- },
- _ => (),
- }
- },
- ExprKind::Closure(.., _) => (),
- ExprKind::Binary(op, _, _) => {
- walk_expr(self, e);
- match op.node {
- BinOpKind::And | BinOpKind::Or => self.short_circuits += 1,
- _ => (),
+ if arms.len() > 1 {
+ self.cc += 1;
}
+ self.cc += arms.iter().filter(|arm| arm.guard.is_some()).count() as u64;
},
ExprKind::Ret(_) => self.returns += 1,
- _ => walk_expr(self, e),
+ _ => {},
}
}
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
NestedVisitorMap::None
}
}
-
-#[cfg(feature = "debugging")]
-#[allow(clippy::too_many_arguments)]
-fn report_cc_bug(
- _: &LateContext<'_, '_>,
- cc: u64,
- narms: u64,
- div: u64,
- shorts: u64,
- returns: u64,
- span: Span,
- _: HirId,
-) {
- span_bug!(
- span,
- "Clippy encountered a bug calculating cognitive complexity: cc = {}, arms = {}, \
- div = {}, shorts = {}, returns = {}. Please file a bug report.",
- cc,
- narms,
- div,
- shorts,
- returns
- );
-}
-#[cfg(not(feature = "debugging"))]
-#[allow(clippy::too_many_arguments)]
-fn report_cc_bug(
- cx: &LateContext<'_, '_>,
- cc: u64,
- narms: u64,
- div: u64,
- shorts: u64,
- returns: u64,
- span: Span,
- id: HirId,
-) {
- if !is_allowed(cx, COGNITIVE_COMPLEXITY, id) {
- cx.sess().span_note_without_error(
- span,
- &format!(
- "Clippy encountered a bug calculating cognitive complexity \
- (hide this message with `#[allow(cognitive_complexity)]`): \
- cc = {}, arms = {}, div = {}, shorts = {}, returns = {}. \
- Please file a bug report.",
- cc, narms, div, shorts, returns
- ),
- );
- }
-}
projects / rust.git / blobdiff