//! Contains utility functions to generate suggestions.
#![deny(clippy::missing_docs_in_private_items)]
-use crate::higher;
-use crate::source::{snippet, snippet_opt, snippet_with_context, snippet_with_macro_callsite};
+use crate::source::{
+ snippet, snippet_opt, snippet_with_applicability, snippet_with_context, snippet_with_macro_callsite,
+};
+use crate::{get_parent_expr_for_hir, higher};
use rustc_ast::util::parser::AssocOp;
use rustc_ast::{ast, token};
use rustc_ast_pretty::pprust::token_kind_to_string;
use rustc_errors::Applicability;
use rustc_hir as hir;
+use rustc_hir::{ExprKind, HirId, MutTy, TyKind};
+use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::{EarlyContext, LateContext, LintContext};
-use rustc_span::source_map::{CharPos, Span};
-use rustc_span::{BytePos, Pos, SyntaxContext};
+use rustc_middle::hir::place::ProjectionKind;
+use rustc_middle::mir::{FakeReadCause, Mutability};
+use rustc_middle::ty;
+use rustc_span::source_map::{BytePos, CharPos, Pos, Span, SyntaxContext};
+use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
use std::borrow::Cow;
use std::convert::TryInto;
use std::fmt::Display;
+use std::iter;
use std::ops::{Add, Neg, Not, Sub};
/// A helper type to build suggestion correctly handling parentheses.
}
}
+/// Suggestion results for handling closure
+/// args dereferencing and borrowing
+pub struct DerefClosure {
+ /// confidence on the built suggestion
+ pub applicability: Applicability,
+ /// gradually built suggestion
+ pub suggestion: String,
+}
+
+/// Build suggestion gradually by handling closure arg specific usages,
+/// such as explicit deref and borrowing cases.
+/// Returns `None` if no such use cases have been triggered in closure body
+///
+/// note: this only works on single line immutable closures with exactly one input parameter.
+pub fn deref_closure_args<'tcx>(cx: &LateContext<'_>, closure: &'tcx hir::Expr<'_>) -> Option<DerefClosure> {
+ if let hir::ExprKind::Closure(_, fn_decl, body_id, ..) = closure.kind {
+ let closure_body = cx.tcx.hir().body(body_id);
+ // is closure arg a type annotated double reference (i.e.: `|x: &&i32| ...`)
+ // a type annotation is present if param `kind` is different from `TyKind::Infer`
+ let closure_arg_is_type_annotated_double_ref = if let TyKind::Rptr(_, MutTy { ty, .. }) = fn_decl.inputs[0].kind
+ {
+ matches!(ty.kind, TyKind::Rptr(_, MutTy { .. }))
+ } else {
+ false
+ };
+
+ let mut visitor = DerefDelegate {
+ cx,
+ closure_span: closure.span,
+ closure_arg_is_type_annotated_double_ref,
+ next_pos: closure.span.lo(),
+ suggestion_start: String::new(),
+ applicability: Applicability::MaybeIncorrect,
+ };
+
+ let fn_def_id = cx.tcx.hir().local_def_id(closure.hir_id);
+ cx.tcx.infer_ctxt().enter(|infcx| {
+ ExprUseVisitor::new(&mut visitor, &infcx, fn_def_id, cx.param_env, cx.typeck_results())
+ .consume_body(closure_body);
+ });
+
+ if !visitor.suggestion_start.is_empty() {
+ return Some(DerefClosure {
+ applicability: visitor.applicability,
+ suggestion: visitor.finish(),
+ });
+ }
+ }
+ None
+}
+
+/// Visitor struct used for tracking down
+/// dereferencing and borrowing of closure's args
+struct DerefDelegate<'a, 'tcx> {
+ /// The late context of the lint
+ cx: &'a LateContext<'tcx>,
+ /// The span of the input closure to adapt
+ closure_span: Span,
+ /// Indicates if the arg of the closure is a type annotated double reference
+ closure_arg_is_type_annotated_double_ref: bool,
+ /// last position of the span to gradually build the suggestion
+ next_pos: BytePos,
+ /// starting part of the gradually built suggestion
+ suggestion_start: String,
+ /// confidence on the built suggestion
+ applicability: Applicability,
+}
+
+impl DerefDelegate<'_, 'tcx> {
+ /// build final suggestion:
+ /// - create the ending part of suggestion
+ /// - concatenate starting and ending parts
+ /// - potentially remove needless borrowing
+ pub fn finish(&mut self) -> String {
+ let end_span = Span::new(self.next_pos, self.closure_span.hi(), self.closure_span.ctxt(), None);
+ let end_snip = snippet_with_applicability(self.cx, end_span, "..", &mut self.applicability);
+ let sugg = format!("{}{}", self.suggestion_start, end_snip);
+ if self.closure_arg_is_type_annotated_double_ref {
+ sugg.replacen('&', "", 1)
+ } else {
+ sugg
+ }
+ }
+
+ /// indicates whether the function from `parent_expr` takes its args by double reference
+ fn func_takes_arg_by_double_ref(&self, parent_expr: &'tcx hir::Expr<'_>, cmt_hir_id: HirId) -> bool {
+ let (call_args, inputs) = match parent_expr.kind {
+ ExprKind::MethodCall(_, _, call_args, _) => {
+ if let Some(method_did) = self.cx.typeck_results().type_dependent_def_id(parent_expr.hir_id) {
+ (call_args, self.cx.tcx.fn_sig(method_did).skip_binder().inputs())
+ } else {
+ return false;
+ }
+ },
+ ExprKind::Call(func, call_args) => {
+ let typ = self.cx.typeck_results().expr_ty(func);
+ (call_args, typ.fn_sig(self.cx.tcx).skip_binder().inputs())
+ },
+ _ => return false,
+ };
+
+ iter::zip(call_args, inputs)
+ .any(|(arg, ty)| arg.hir_id == cmt_hir_id && matches!(ty.kind(), ty::Ref(_, inner, _) if inner.is_ref()))
+ }
+}
+
+impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
+ fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
+
+ #[allow(clippy::too_many_lines)]
+ fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, _: ty::BorrowKind) {
+ if let PlaceBase::Local(id) = cmt.place.base {
+ let map = self.cx.tcx.hir();
+ let span = map.span(cmt.hir_id);
+ let start_span = Span::new(self.next_pos, span.lo(), span.ctxt(), None);
+ let mut start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
+
+ // identifier referring to the variable currently triggered (i.e.: `fp`)
+ let ident_str = map.name(id).to_string();
+ // full identifier that includes projection (i.e.: `fp.field`)
+ let ident_str_with_proj = snippet(self.cx, span, "..").to_string();
+
+ if cmt.place.projections.is_empty() {
+ // handle item without any projection, that needs an explicit borrowing
+ // i.e.: suggest `&x` instead of `x`
+ self.suggestion_start.push_str(&format!("{}&{}", start_snip, ident_str));
+ } else {
+ // cases where a parent `Call` or `MethodCall` is using the item
+ // i.e.: suggest `.contains(&x)` for `.find(|x| [1, 2, 3].contains(x)).is_none()`
+ //
+ // Note about method calls:
+ // - compiler automatically dereference references if the target type is a reference (works also for
+ // function call)
+ // - `self` arguments in the case of `x.is_something()` are also automatically (de)referenced, and
+ // no projection should be suggested
+ if let Some(parent_expr) = get_parent_expr_for_hir(self.cx, cmt.hir_id) {
+ match &parent_expr.kind {
+ // given expression is the self argument and will be handled completely by the compiler
+ // i.e.: `|x| x.is_something()`
+ ExprKind::MethodCall(_, _, [self_expr, ..], _) if self_expr.hir_id == cmt.hir_id => {
+ self.suggestion_start
+ .push_str(&format!("{}{}", start_snip, ident_str_with_proj));
+ self.next_pos = span.hi();
+ return;
+ },
+ // item is used in a call
+ // i.e.: `Call`: `|x| please(x)` or `MethodCall`: `|x| [1, 2, 3].contains(x)`
+ ExprKind::Call(_, [call_args @ ..]) | ExprKind::MethodCall(_, _, [_, call_args @ ..], _) => {
+ let expr = self.cx.tcx.hir().expect_expr(cmt.hir_id);
+ let arg_ty_kind = self.cx.typeck_results().expr_ty(expr).kind();
+
+ if matches!(arg_ty_kind, ty::Ref(_, _, Mutability::Not)) {
+ // suggest ampersand if call function is taking args by double reference
+ let takes_arg_by_double_ref =
+ self.func_takes_arg_by_double_ref(parent_expr, cmt.hir_id);
+
+ // compiler will automatically dereference field or index projection, so no need
+ // to suggest ampersand, but full identifier that includes projection is required
+ let has_field_or_index_projection =
+ cmt.place.projections.iter().any(|proj| {
+ matches!(proj.kind, ProjectionKind::Field(..) | ProjectionKind::Index)
+ });
+
+ // no need to bind again if the function doesn't take arg by double ref
+ // and if the item is already a double ref
+ let ident_sugg = if !call_args.is_empty()
+ && !takes_arg_by_double_ref
+ && (self.closure_arg_is_type_annotated_double_ref || has_field_or_index_projection)
+ {
+ let ident = if has_field_or_index_projection {
+ ident_str_with_proj
+ } else {
+ ident_str
+ };
+ format!("{}{}", start_snip, ident)
+ } else {
+ format!("{}&{}", start_snip, ident_str)
+ };
+ self.suggestion_start.push_str(&ident_sugg);
+ self.next_pos = span.hi();
+ return;
+ }
+
+ self.applicability = Applicability::Unspecified;
+ },
+ _ => (),
+ }
+ }
+
+ let mut replacement_str = ident_str;
+ let mut projections_handled = false;
+ cmt.place.projections.iter().enumerate().for_each(|(i, proj)| {
+ match proj.kind {
+ // Field projection like `|v| v.foo`
+ // no adjustment needed here, as field projections are handled by the compiler
+ ProjectionKind::Field(..) => match cmt.place.ty_before_projection(i).kind() {
+ ty::Adt(..) | ty::Tuple(_) => {
+ replacement_str = ident_str_with_proj.clone();
+ projections_handled = true;
+ },
+ _ => (),
+ },
+ // Index projection like `|x| foo[x]`
+ // the index is dropped so we can't get it to build the suggestion,
+ // so the span is set-up again to get more code, using `span.hi()` (i.e.: `foo[x]`)
+ // instead of `span.lo()` (i.e.: `foo`)
+ ProjectionKind::Index => {
+ let start_span = Span::new(self.next_pos, span.hi(), span.ctxt(), None);
+ start_snip = snippet_with_applicability(self.cx, start_span, "..", &mut self.applicability);
+ replacement_str.clear();
+ projections_handled = true;
+ },
+ // note: unable to trigger `Subslice` kind in tests
+ ProjectionKind::Subslice => (),
+ ProjectionKind::Deref => {
+ // Explicit derefs are typically handled later on, but
+ // some items do not need explicit deref, such as array accesses,
+ // so we mark them as already processed
+ // i.e.: don't suggest `*sub[1..4].len()` for `|sub| sub[1..4].len() == 3`
+ if let ty::Ref(_, inner, _) = cmt.place.ty_before_projection(i).kind() {
+ if matches!(inner.kind(), ty::Ref(_, innermost, _) if innermost.is_array()) {
+ projections_handled = true;
+ }
+ }
+ },
+ }
+ });
+
+ // handle `ProjectionKind::Deref` by removing one explicit deref
+ // if no special case was detected (i.e.: suggest `*x` instead of `**x`)
+ if !projections_handled {
+ let last_deref = cmt
+ .place
+ .projections
+ .iter()
+ .rposition(|proj| proj.kind == ProjectionKind::Deref);
+
+ if let Some(pos) = last_deref {
+ let mut projections = cmt.place.projections.clone();
+ projections.truncate(pos);
+
+ for item in projections {
+ if item.kind == ProjectionKind::Deref {
+ replacement_str = format!("*{}", replacement_str);
+ }
+ }
+ }
+ }
+
+ self.suggestion_start
+ .push_str(&format!("{}{}", start_snip, replacement_str));
+ }
+ self.next_pos = span.hi();
+ }
+ }
+
+ fn mutate(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
+
+ fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _: HirId) {}
+}
+
#[cfg(test)]
mod test {
use super::Sugg;
projects / rust.git / blobdiff