Auto merge of rust-lang#7938 - camsteffen:visitors, r=xFrednet

Introduce `expr_visitor` and `expr_visitor_no_bodies`

changelog: none

A couple utils that satisfy a *lot* of visitor use cases. Factoring in every possible usage would be really big so I just focused on cleaning clippy_utils.

clippy_lints/src/eta_reduction.rs

@@ -1,8 +1,8 @@
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::higher::VecArgs;
 use clippy_utils::source::snippet_opt;
-use clippy_utils::usage::UsedAfterExprVisitor;
-use clippy_utils::{get_enclosing_loop_or_closure, higher, path_to_local_id};
+use clippy_utils::usage::local_used_after_expr;
+use clippy_utils::{get_enclosing_loop_or_closure, higher, path_to_local, path_to_local_id};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::def_id::DefId;
@@ -118,7 +118,7 @@ impl<'tcx> LateLintPass<'tcx> for EtaReduction {
                             if let ty::Closure(_, substs) = callee_ty.peel_refs().kind();
                             if substs.as_closure().kind() == ClosureKind::FnMut;
                             if get_enclosing_loop_or_closure(cx.tcx, expr).is_some()
-                                || UsedAfterExprVisitor::is_found(cx, callee);
+                                || path_to_local(callee).map_or(false, |l| local_used_after_expr(cx, l, callee));
 
                             then {
                                 // Mutable closure is used after current expr; we cannot consume it.

clippy_lints/src/format_args.rs

@@ -10,7 +10,7 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment};
 use rustc_middle::ty::Ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
-use rustc_span::{sym, BytePos, ExpnData, ExpnKind, Span, Symbol};
+use rustc_span::{sym, ExpnData, ExpnKind, Span, Symbol};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -128,7 +128,7 @@ fn check_format_in_format_args(cx: &LateContext<'_>, call_site: Span, name: Symb
             span_lint_and_then(
                 cx,
                 FORMAT_IN_FORMAT_ARGS,
-                trim_semicolon(cx, call_site),
+                call_site,
                 &format!("`format!` in `{}!` args", name),
                 |diag| {
                     diag.help(&format!(
@@ -192,13 +192,6 @@ fn is_aliased(args: &[FormatArgsArg<'_>], i: usize) -> bool {
         .any(|(j, arg)| i != j && std::ptr::eq(value, arg.value))
 }
 
-fn trim_semicolon(cx: &LateContext<'_>, span: Span) -> Span {
-    snippet_opt(cx, span).map_or(span, |snippet| {
-        let snippet = snippet.trim_end_matches(';');
-        span.with_hi(span.lo() + BytePos(u32::try_from(snippet.len()).unwrap()))
-    })
-}
-
 fn count_needed_derefs<'tcx, I>(mut ty: Ty<'tcx>, mut iter: I) -> (usize, Ty<'tcx>)
 where
     I: Iterator<Item = &'tcx Adjustment<'tcx>>,

clippy_lints/src/implicit_return.rs

@@ -2,10 +2,10 @@ use clippy_utils::{
     diagnostics::span_lint_and_sugg,
     get_async_fn_body, is_async_fn,
     source::{snippet_with_applicability, snippet_with_context, walk_span_to_context},
-    visitors::visit_break_exprs,
+    visitors::expr_visitor_no_bodies,
 };
 use rustc_errors::Applicability;
-use rustc_hir::intravisit::FnKind;
+use rustc_hir::intravisit::{FnKind, Visitor};
 use rustc_hir::{Block, Body, Expr, ExprKind, FnDecl, FnRetTy, HirId};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
@@ -144,20 +144,24 @@ fn lint_implicit_returns(
 
         ExprKind::Loop(block, ..) => {
             let mut add_return = false;
-            visit_break_exprs(block, |break_expr, dest, sub_expr| {
-                if dest.target_id.ok() == Some(expr.hir_id) {
-                    if call_site_span.is_none() && break_expr.span.ctxt() == ctxt {
-                        // At this point sub_expr can be `None` in async functions which either diverge, or return the
-                        // unit type.
-                        if let Some(sub_expr) = sub_expr {
-                            lint_break(cx, break_expr.span, sub_expr.span);
+            expr_visitor_no_bodies(|e| {
+                if let ExprKind::Break(dest, sub_expr) = e.kind {
+                    if dest.target_id.ok() == Some(expr.hir_id) {
+                        if call_site_span.is_none() && e.span.ctxt() == ctxt {
+                            // At this point sub_expr can be `None` in async functions which either diverge, or return
+                            // the unit type.
+                            if let Some(sub_expr) = sub_expr {
+                                lint_break(cx, e.span, sub_expr.span);
+                            }
+                        } else {
+                            // the break expression is from a macro call, add a return to the loop
+                            add_return = true;
                         }
-                    } else {
-                        // the break expression is from a macro call, add a return to the loop
-                        add_return = true;
                     }
                 }
-            });
+                true
+            })
+            .visit_block(block);
             if add_return {
                 #[allow(clippy::option_if_let_else)]
                 if let Some(span) = call_site_span {

clippy_lints/src/matches.rs

@@ -632,9 +632,6 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
         if let ExprKind::Match(ex, arms, _) = expr.kind {
             check_match_ref_pats(cx, ex, arms.iter().map(|el| el.pat), expr);
         }
-        if let Some(higher::IfLet { let_pat, let_expr, .. }) = higher::IfLet::hir(cx, expr) {
-            check_match_ref_pats(cx, let_expr, once(let_pat), expr);
-        }
     }
 
     fn check_local(&mut self, cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {

clippy_utils/src/lib.rs

@@ -1,6 +1,7 @@
 #![feature(box_patterns)]
 #![feature(in_band_lifetimes)]
 #![feature(iter_zip)]
+#![feature(let_else)]
 #![feature(rustc_private)]
 #![feature(control_flow_enum)]
 #![recursion_limit = "512"]
@@ -68,7 +69,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::hir_id::{HirIdMap, HirIdSet};
-use rustc_hir::intravisit::{self, walk_expr, ErasedMap, FnKind, NestedVisitorMap, Visitor};
+use rustc_hir::intravisit::{walk_expr, ErasedMap, FnKind, NestedVisitorMap, Visitor};
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_hir::LangItem::{OptionNone, ResultErr, ResultOk};
 use rustc_hir::{
@@ -96,6 +97,7 @@ use rustc_target::abi::Integer;
 
 use crate::consts::{constant, Constant};
 use crate::ty::{can_partially_move_ty, is_copy, is_recursively_primitive_type};
+use crate::visitors::expr_visitor_no_bodies;
 
 pub fn parse_msrv(msrv: &str, sess: Option<&Session>, span: Option<Span>) -> Option<RustcVersion> {
     if let Ok(version) = RustcVersion::parse(msrv) {
@@ -1107,63 +1109,30 @@ pub fn contains_name(name: Symbol, expr: &Expr<'_>) -> bool {
 
 /// Returns `true` if `expr` contains a return expression
 pub fn contains_return(expr: &hir::Expr<'_>) -> bool {
-    struct RetCallFinder {
-        found: bool,
-    }
-
-    impl<'tcx> hir::intravisit::Visitor<'tcx> for RetCallFinder {
-        type Map = Map<'tcx>;
-
-        fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
-            if self.found {
-                return;
-            }
+    let mut found = false;
+    expr_visitor_no_bodies(|expr| {
+        if !found {
             if let hir::ExprKind::Ret(..) = &expr.kind {
-                self.found = true;
-            } else {
-                hir::intravisit::walk_expr(self, expr);
+                found = true;
             }
         }
-
-        fn nested_visit_map(&mut self) -> hir::intravisit::NestedVisitorMap<Self::Map> {
-            hir::intravisit::NestedVisitorMap::None
-        }
-    }
-
-    let mut visitor = RetCallFinder { found: false };
-    visitor.visit_expr(expr);
-    visitor.found
-}
-
-struct FindMacroCalls<'a, 'b> {
-    names: &'a [&'b str],
-    result: Vec<Span>,
-}
-
-impl<'a, 'b, 'tcx> Visitor<'tcx> for FindMacroCalls<'a, 'b> {
-    type Map = Map<'tcx>;
-
-    fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
-        if self.names.iter().any(|fun| is_expn_of(expr.span, fun).is_some()) {
-            self.result.push(expr.span);
-        }
-        // and check sub-expressions
-        intravisit::walk_expr(self, expr);
-    }
-
-    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
-        NestedVisitorMap::None
-    }
+        !found
+    })
+    .visit_expr(expr);
+    found
 }
 
 /// Finds calls of the specified macros in a function body.
 pub fn find_macro_calls(names: &[&str], body: &Body<'_>) -> Vec<Span> {
-    let mut fmc = FindMacroCalls {
-        names,
-        result: Vec::new(),
-    };
-    fmc.visit_expr(&body.value);
-    fmc.result
+    let mut result = Vec::new();
+    expr_visitor_no_bodies(|expr| {
+        if names.iter().any(|fun| is_expn_of(expr.span, fun).is_some()) {
+            result.push(expr.span);
+        }
+        true
+    })
+    .visit_expr(&body.value);
+    result
 }
 
 /// Extends the span to the beginning of the spans line, incl. whitespaces.

clippy_utils/src/ptr.rs

@@ -1,9 +1,9 @@
 use crate::source::snippet;
+use crate::visitors::expr_visitor_no_bodies;
 use crate::{path_to_local_id, strip_pat_refs};
-use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
-use rustc_hir::{Body, BodyId, Expr, ExprKind, HirId, PatKind};
+use rustc_hir::intravisit::Visitor;
+use rustc_hir::{Body, BodyId, ExprKind, HirId, PatKind};
 use rustc_lint::LateContext;
-use rustc_middle::hir::map::Map;
 use rustc_span::Span;
 use std::borrow::Cow;
 
@@ -30,50 +30,28 @@ fn extract_clone_suggestions<'tcx>(
     replace: &[(&'static str, &'static str)],
     body: &'tcx Body<'_>,
 ) -> Option<Vec<(Span, Cow<'static, str>)>> {
-    let mut visitor = PtrCloneVisitor {
-        cx,
-        id,
-        replace,
-        spans: vec![],
-        abort: false,
-    };
-    visitor.visit_body(body);
-    if visitor.abort { None } else { Some(visitor.spans) }
-}
-
-struct PtrCloneVisitor<'a, 'tcx> {
-    cx: &'a LateContext<'tcx>,
-    id: HirId,
-    replace: &'a [(&'static str, &'static str)],
-    spans: Vec<(Span, Cow<'static, str>)>,
-    abort: bool,
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for PtrCloneVisitor<'a, 'tcx> {
-    type Map = Map<'tcx>;
-
-    fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
-        if self.abort {
-            return;
+    let mut abort = false;
+    let mut spans = Vec::new();
+    expr_visitor_no_bodies(|expr| {
+        if abort {
+            return false;
         }
         if let ExprKind::MethodCall(seg, _, [recv], _) = expr.kind {
-            if path_to_local_id(recv, self.id) {
+            if path_to_local_id(recv, id) {
                 if seg.ident.name.as_str() == "capacity" {
-                    self.abort = true;
-                    return;
+                    abort = true;
+                    return false;
                 }
-                for &(fn_name, suffix) in self.replace {
+                for &(fn_name, suffix) in replace {
                     if seg.ident.name.as_str() == fn_name {
-                        self.spans.push((expr.span, snippet(self.cx, recv.span, "_") + suffix));
-                        return;
+                        spans.push((expr.span, snippet(cx, recv.span, "_") + suffix));
+                        return false;
                     }
                 }
             }
         }
-        walk_expr(self, expr);
-    }
-
-    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
-        NestedVisitorMap::None
-    }
+        !abort
+    })
+    .visit_body(body);
+    if abort { None } else { Some(spans) }
 }