Auto merge of #4123 - Centril:rustup-let-chains-ast, r=Manishearth

Fix fallout from rust-lang/rust PR 60861

Fixes incoming breakage for unlanded rust-lang/rust#60861.

Tests are passing locally; the Rust PR now needs to land first.

@Manishearth also says we'll want to split out to a `collapsible_if_let` once we have let-chains working in Rust nightly or something.

clippy_lints/src/collapsible_if.rs

@@ -84,18 +84,14 @@ impl EarlyLintPass for CollapsibleIf {
 }
 
 fn check_if(cx: &EarlyContext<'_>, expr: &ast::Expr) {
- match expr.node {
- ast::ExprKind::If(ref check, ref then, ref else_) => {
- if let Some(ref else_) = *else_ {
- check_collapsible_maybe_if_let(cx, else_);
- } else {
- check_collapsible_no_if_let(cx, expr, check, then);
- }
- },
- ast::ExprKind::IfLet(_, _, _, Some(ref else_)) => {
+ if let ast::ExprKind::If(check, then, else_) = &expr.node {
+ if let Some(else_) = else_ {
  check_collapsible_maybe_if_let(cx, else_);
- },
- _ => (),
+ } else if let ast::ExprKind::Let(..) = check.node {
+ // Prevent triggering on `if let a = b { if c { .. } }`.
+ } else {
+ check_collapsible_no_if_let(cx, expr, check, then);
+ }
  }
 }
 
@@ -113,22 +109,18 @@ fn check_collapsible_maybe_if_let(cx: &EarlyContext<'_>, else_: &ast::Expr) {
  if !block_starts_with_comment(cx, block);
  if let Some(else_) = expr_block(block);
  if !in_macro_or_desugar(else_.span);
+ if let ast::ExprKind::If(..) = else_.node;
  then {
- match else_.node {
- ast::ExprKind::If(..) | ast::ExprKind::IfLet(..) => {
- let mut applicability = Applicability::MachineApplicable;
- span_lint_and_sugg(
- cx,
- COLLAPSIBLE_IF,
- block.span,
- "this `else { if .. }` block can be collapsed",
- "try",
- snippet_block_with_applicability(cx, else_.span, "..", &mut applicability).into_owned(),
- applicability,
- );
- }
- _ => (),
- }
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ COLLAPSIBLE_IF,
+ block.span,
+ "this `else { if .. }` block can be collapsed",
+ "try",
+ snippet_block_with_applicability(cx, else_.span, "..", &mut applicability).into_owned(),
+ applicability,
+ );
  }
  }
 }
@@ -139,6 +131,11 @@ fn check_collapsible_no_if_let(cx: &EarlyContext<'_>, expr: &ast::Expr, check: &
  if let Some(inner) = expr_block(then);
  if let ast::ExprKind::If(ref check_inner, ref content, None) = inner.node;
  then {
+ if let ast::ExprKind::Let(..) = check_inner.node {
+ // Prevent triggering on `if c { if let a = b { .. } }`.
+ return;
+ }
+
  if expr.span.ctxt() != inner.span.ctxt() {
  return;
  }

clippy_lints/src/formatting.rs

@@ -248,9 +248,7 @@ fn is_block(expr: &ast::Expr) -> bool {
 /// Match `if` or `if let` expressions and return the `then` and `else` block.
 fn unsugar_if(expr: &ast::Expr) -> Option<(&P<ast::Block>, &Option<P<ast::Expr>>)> {
  match expr.node {
- ast::ExprKind::If(_, ref then, ref else_) | ast::ExprKind::IfLet(_, _, ref then, ref else_) => {
- Some((then, else_))
- },
+ ast::ExprKind::If(_, ref then, ref else_) => Some((then, else_)),
  _ => None,
  }
 }

clippy_lints/src/identity_conversion.rs

@@ -50,8 +50,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityConversion {
  };
  if let ExprKind::Call(_, ref args) = e.node {
  self.try_desugar_arm.push(args[0].hir_id);
- } else {
- return;
  }
  },
 

clippy_lints/src/needless_continue.rs

@@ -209,12 +209,11 @@ fn with_loop_block<F>(expr: &ast::Expr, mut func: F)
 where
  F: FnMut(&ast::Block, Option<&ast::Label>),
 {
- match expr.node {
- ast::ExprKind::While(_, ref loop_block, ref label)
- | ast::ExprKind::WhileLet(_, _, ref loop_block, ref label)
- | ast::ExprKind::ForLoop(_, _, ref loop_block, ref label)
- | ast::ExprKind::Loop(ref loop_block, ref label) => func(loop_block, label.as_ref()),
- _ => {},
+ if let ast::ExprKind::While(_, loop_block, label)
+ | ast::ExprKind::ForLoop(_, _, loop_block, label)
+ | ast::ExprKind::Loop(loop_block, label) = &expr.node
+ {
+ func(loop_block, label.as_ref());
  }
 }
 

clippy_lints/src/utils/sugg.rs

@@ -135,7 +135,7 @@ impl<'a> Sugg<'a> {
  | ast::ExprKind::Box(..)
  | ast::ExprKind::Closure(..)
  | ast::ExprKind::If(..)
- | ast::ExprKind::IfLet(..)
+ | ast::ExprKind::Let(..)
  | ast::ExprKind::Unary(..)
  | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
  ast::ExprKind::Async(..)
@@ -162,7 +162,6 @@ impl<'a> Sugg<'a> {
  | ast::ExprKind::Tup(..)
  | ast::ExprKind::Array(..)
  | ast::ExprKind::While(..)
- | ast::ExprKind::WhileLet(..)
  | ast::ExprKind::Await(..)
  | ast::ExprKind::Err => Sugg::NonParen(snippet),
  ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),

clippy_lints/src/utils/usage.rs

@@ -37,7 +37,7 @@ pub fn is_potentially_mutated<'a, 'tcx>(variable: &'tcx Path, expr: &'tcx Expr,
  if let Res::Local(id) = variable.res {
  mutated_variables(expr, cx).map_or(true, |mutated| mutated.contains(&id))
  } else {
- return true;
+ true
  }
 }
 

tests/ui/collapsible_if.fixed

@@ -172,4 +172,25 @@ else {
  println!("Hello world!");
  }
  }
+
+ // Test behavior wrt. `let_chains`.
+ // None of the cases below should be collapsed.
+ fn truth() -> bool { true }
+
+ // Prefix:
+ if let 0 = 1 {
+ if truth() {}
+ }
+
+ // Suffix:
+ if truth() {
+ if let 0 = 1 {}
+ }
+
+ // Midfix:
+ if truth() {
+ if let 0 = 1 {
+ if truth() {}
+ }
+ }
 }

tests/ui/collapsible_if.rs

@@ -200,4 +200,25 @@ fn main() {
  println!("Hello world!");
  }
  }
+
+ // Test behavior wrt. `let_chains`.
+ // None of the cases below should be collapsed.
+ fn truth() -> bool { true }
+
+ // Prefix:
+ if let 0 = 1 {
+ if truth() {}
+ }
+
+ // Suffix:
+ if truth() {
+ if let 0 = 1 {}
+ }
+
+ // Midfix:
+ if truth() {
+ if let 0 = 1 {
+ if truth() {}
+ }
+ }
 }