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Auto merge of #62075 - Centril:guardless-match-arms, r=petrochenkov
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Remove `ast::Guard`

With the introduction of `ast::ExprKind::Let` in #60861, the `ast::Guard` structure is now redundant in terms of representing [`if let` guards](#51114) in AST since it can be represented by `ExprKind::Let` syntactically. Therefore, we remove `ast::Guard` here.

However, we keep `hir::Guard` because the semantic representation is a different matter and this story is more unclear right now (might involve `goto 'arm` in HIR or something...).

r? @petrochenkov
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bors committed Jun 24, 2019
2 parents 85ed21e + 4d53714 commit 3cc3486
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Showing 8 changed files with 14 additions and 36 deletions.
2 changes: 1 addition & 1 deletion src/librustc/hir/lowering.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1382,7 +1382,7 @@ impl<'a> LoweringContext<'a> {
attrs: self.lower_attrs(&arm.attrs),
pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
guard: match arm.guard {
Some(Guard::If(ref x)) => Some(hir::Guard::If(P(self.lower_expr(x)))),
Some(ref x) => Some(hir::Guard::If(P(self.lower_expr(x)))),
_ => None,
},
body: P(self.lower_expr(&arm.body)),
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2 changes: 1 addition & 1 deletion src/librustc_resolve/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3055,7 +3055,7 @@ impl<'a> Resolver<'a> {

self.resolve_pats(&arm.pats, PatternSource::Match);

if let Some(ast::Guard::If(ref expr)) = arm.guard {
if let Some(ref expr) = arm.guard {
self.visit_expr(expr)
}
self.visit_expr(&arm.body);
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5 changes: 2 additions & 3 deletions src/librustc_save_analysis/dump_visitor.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1609,9 +1609,8 @@ impl<'l, 'tcx, 'll, O: DumpOutput + 'll> Visitor<'l> for DumpVisitor<'l, 'tcx, '

fn visit_arm(&mut self, arm: &'l ast::Arm) {
self.process_var_decl_multi(&arm.pats);
match arm.guard {
Some(ast::Guard::If(ref expr)) => self.visit_expr(expr),
_ => {}
if let Some(expr) = &arm.guard {
self.visit_expr(expr);
}
self.visit_expr(&arm.body);
}
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7 changes: 1 addition & 6 deletions src/libsyntax/ast.rs
Original file line number Diff line number Diff line change
Expand Up @@ -893,16 +893,11 @@ pub struct Local {
pub struct Arm {
pub attrs: Vec<Attribute>,
pub pats: Vec<P<Pat>>,
pub guard: Option<Guard>,
pub guard: Option<P<Expr>>,
pub body: P<Expr>,
pub span: Span,
}

#[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
pub enum Guard {
If(P<Expr>),
}

#[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
pub struct Field {
pub ident: Ident,
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12 changes: 1 addition & 11 deletions src/libsyntax/mut_visit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -131,10 +131,6 @@ pub trait MutVisitor: Sized {
noop_visit_arm(a, self);
}

fn visit_guard(&mut self, g: &mut Guard) {
noop_visit_guard(g, self);
}

fn visit_pat(&mut self, p: &mut P<Pat>) {
noop_visit_pat(p, self);
}
Expand Down Expand Up @@ -389,17 +385,11 @@ pub fn noop_visit_arm<T: MutVisitor>(
) {
visit_attrs(attrs, vis);
visit_vec(pats, |pat| vis.visit_pat(pat));
visit_opt(guard, |guard| vis.visit_guard(guard));
visit_opt(guard, |guard| vis.visit_expr(guard));
vis.visit_expr(body);
vis.visit_span(span);
}

pub fn noop_visit_guard<T: MutVisitor>(g: &mut Guard, vis: &mut T) {
match g {
Guard::If(e) => vis.visit_expr(e),
}
}

pub fn noop_visit_ty_constraint<T: MutVisitor>(
AssocTyConstraint { id, ident, kind, span }: &mut AssocTyConstraint,
vis: &mut T
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4 changes: 2 additions & 2 deletions src/libsyntax/parse/parser.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy};
use crate::ast::{GenericBound, TraitBoundModifier};
use crate::ast::Unsafety;
use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind};
use crate::ast::{Mod, AnonConst, Arg, Arm, Attribute, BindingMode, TraitItemKind};
use crate::ast::Block;
use crate::ast::{BlockCheckMode, CaptureBy, Movability};
use crate::ast::{Constness, Crate};
Expand Down Expand Up @@ -3396,7 +3396,7 @@ impl<'a> Parser<'a> {
let lo = self.token.span;
let pats = self.parse_pats()?;
let guard = if self.eat_keyword(kw::If) {
Some(Guard::If(self.parse_expr()?))
Some(self.parse_expr()?)
} else {
None
};
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12 changes: 4 additions & 8 deletions src/libsyntax/print/pprust.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2653,14 +2653,10 @@ impl<'a> State<'a> {
self.print_outer_attributes(&arm.attrs)?;
self.print_pats(&arm.pats)?;
self.s.space()?;
if let Some(ref g) = arm.guard {
match g {
ast::Guard::If(ref e) => {
self.word_space("if")?;
self.print_expr(e)?;
self.s.space()?;
}
}
if let Some(ref e) = arm.guard {
self.word_space("if")?;
self.print_expr(e)?;
self.s.space()?;
}
self.word_space("=>")?;

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6 changes: 2 additions & 4 deletions src/libsyntax/visit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -826,10 +826,8 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {

pub fn walk_arm<'a, V: Visitor<'a>>(visitor: &mut V, arm: &'a Arm) {
walk_list!(visitor, visit_pat, &arm.pats);
if let Some(ref g) = &arm.guard {
match g {
Guard::If(ref e) => visitor.visit_expr(e),
}
if let Some(ref e) = &arm.guard {
visitor.visit_expr(e);
}
visitor.visit_expr(&arm.body);
walk_list!(visitor, visit_attribute, &arm.attrs);
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