| use super::{ImplTraitContext, LoweringContext, ParamMode}; |
| |
| use rustc_hir as hir; |
| use rustc_hir::def::Res; |
| use rustc_span::{source_map::Spanned, Span}; |
| use syntax::ast::*; |
| use syntax::ptr::P; |
| |
| impl<'a, 'hir> LoweringContext<'a, 'hir> { |
| crate fn lower_pat(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> { |
| let node = match p.kind { |
| PatKind::Wild => hir::PatKind::Wild, |
| PatKind::Ident(ref binding_mode, ident, ref sub) => { |
| let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(&*s)); |
| let node = self.lower_pat_ident(p, binding_mode, ident, lower_sub); |
| node |
| } |
| PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)), |
| PatKind::TupleStruct(ref path, ref pats) => { |
| let qpath = self.lower_qpath( |
| p.id, |
| &None, |
| path, |
| ParamMode::Optional, |
| ImplTraitContext::disallowed(), |
| ); |
| let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct"); |
| hir::PatKind::TupleStruct(qpath, pats, ddpos) |
| } |
| PatKind::Or(ref pats) => { |
| hir::PatKind::Or(self.arena.alloc_from_iter(pats.iter().map(|x| self.lower_pat(x)))) |
| } |
| PatKind::Path(ref qself, ref path) => { |
| let qpath = self.lower_qpath( |
| p.id, |
| qself, |
| path, |
| ParamMode::Optional, |
| ImplTraitContext::disallowed(), |
| ); |
| hir::PatKind::Path(qpath) |
| } |
| PatKind::Struct(ref path, ref fields, etc) => { |
| let qpath = self.lower_qpath( |
| p.id, |
| &None, |
| path, |
| ParamMode::Optional, |
| ImplTraitContext::disallowed(), |
| ); |
| |
| let fs = self.arena.alloc_from_iter(fields.iter().map(|f| hir::FieldPat { |
| hir_id: self.next_id(), |
| ident: f.ident, |
| pat: self.lower_pat(&f.pat), |
| is_shorthand: f.is_shorthand, |
| span: f.span, |
| })); |
| hir::PatKind::Struct(qpath, fs, etc) |
| } |
| PatKind::Tuple(ref pats) => { |
| let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple"); |
| hir::PatKind::Tuple(pats, ddpos) |
| } |
| PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)), |
| PatKind::Ref(ref inner, mutbl) => hir::PatKind::Ref(self.lower_pat(inner), mutbl), |
| PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range( |
| e1.as_deref().map(|e| self.lower_expr(e)), |
| e2.as_deref().map(|e| self.lower_expr(e)), |
| self.lower_range_end(end, e2.is_some()), |
| ), |
| PatKind::Slice(ref pats) => self.lower_pat_slice(pats), |
| PatKind::Rest => { |
| // If we reach here the `..` pattern is not semantically allowed. |
| self.ban_illegal_rest_pat(p.span) |
| } |
| PatKind::Paren(ref inner) => return self.lower_pat(inner), |
| PatKind::Mac(_) => panic!("Shouldn't exist here"), |
| }; |
| |
| self.pat_with_node_id_of(p, node) |
| } |
| |
| fn lower_pat_tuple( |
| &mut self, |
| pats: &[P<Pat>], |
| ctx: &str, |
| ) -> (&'hir [&'hir hir::Pat<'hir>], Option<usize>) { |
| let mut elems = Vec::with_capacity(pats.len()); |
| let mut rest = None; |
| |
| let mut iter = pats.iter().enumerate(); |
| for (idx, pat) in iter.by_ref() { |
| // Interpret the first `..` pattern as a sub-tuple pattern. |
| // Note that unlike for slice patterns, |
| // where `xs @ ..` is a legal sub-slice pattern, |
| // it is not a legal sub-tuple pattern. |
| if pat.is_rest() { |
| rest = Some((idx, pat.span)); |
| break; |
| } |
| // It was not a sub-tuple pattern so lower it normally. |
| elems.push(self.lower_pat(pat)); |
| } |
| |
| for (_, pat) in iter { |
| // There was a previous sub-tuple pattern; make sure we don't allow more... |
| if pat.is_rest() { |
| // ...but there was one again, so error. |
| self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx); |
| } else { |
| elems.push(self.lower_pat(pat)); |
| } |
| } |
| |
| (self.arena.alloc_from_iter(elems), rest.map(|(ddpos, _)| ddpos)) |
| } |
| |
| /// Lower a slice pattern of form `[pat_0, ..., pat_n]` into |
| /// `hir::PatKind::Slice(before, slice, after)`. |
| /// |
| /// When encountering `($binding_mode $ident @)? ..` (`slice`), |
| /// this is interpreted as a sub-slice pattern semantically. |
| /// Patterns that follow, which are not like `slice` -- or an error occurs, are in `after`. |
| fn lower_pat_slice(&mut self, pats: &[P<Pat>]) -> hir::PatKind<'hir> { |
| let mut before = Vec::new(); |
| let mut after = Vec::new(); |
| let mut slice = None; |
| let mut prev_rest_span = None; |
| |
| let mut iter = pats.iter(); |
| // Lower all the patterns until the first occurrence of a sub-slice pattern. |
| for pat in iter.by_ref() { |
| match pat.kind { |
| // Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here. |
| PatKind::Rest => { |
| prev_rest_span = Some(pat.span); |
| slice = Some(self.pat_wild_with_node_id_of(pat)); |
| break; |
| } |
| // Found a sub-slice pattern `$binding_mode $ident @ ..`. |
| // Record, lower it to `$binding_mode $ident @ _`, and stop here. |
| PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => { |
| prev_rest_span = Some(sub.span); |
| let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub)); |
| let node = self.lower_pat_ident(pat, bm, ident, lower_sub); |
| slice = Some(self.pat_with_node_id_of(pat, node)); |
| break; |
| } |
| // It was not a subslice pattern so lower it normally. |
| _ => before.push(self.lower_pat(pat)), |
| } |
| } |
| |
| // Lower all the patterns after the first sub-slice pattern. |
| for pat in iter { |
| // There was a previous subslice pattern; make sure we don't allow more. |
| let rest_span = match pat.kind { |
| PatKind::Rest => Some(pat.span), |
| PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => { |
| // The `HirValidator` is merciless; add a `_` pattern to avoid ICEs. |
| after.push(self.pat_wild_with_node_id_of(pat)); |
| Some(sub.span) |
| } |
| _ => None, |
| }; |
| if let Some(rest_span) = rest_span { |
| // We have e.g., `[a, .., b, ..]`. That's no good, error! |
| self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice"); |
| } else { |
| // Lower the pattern normally. |
| after.push(self.lower_pat(pat)); |
| } |
| } |
| |
| hir::PatKind::Slice( |
| self.arena.alloc_from_iter(before), |
| slice, |
| self.arena.alloc_from_iter(after), |
| ) |
| } |
| |
| fn lower_pat_ident( |
| &mut self, |
| p: &Pat, |
| binding_mode: &BindingMode, |
| ident: Ident, |
| lower_sub: impl FnOnce(&mut Self) -> Option<&'hir hir::Pat<'hir>>, |
| ) -> hir::PatKind<'hir> { |
| match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) { |
| // `None` can occur in body-less function signatures |
| res @ None | res @ Some(Res::Local(_)) => { |
| let canonical_id = match res { |
| Some(Res::Local(id)) => id, |
| _ => p.id, |
| }; |
| |
| hir::PatKind::Binding( |
| self.lower_binding_mode(binding_mode), |
| self.lower_node_id(canonical_id), |
| ident, |
| lower_sub(self), |
| ) |
| } |
| Some(res) => hir::PatKind::Path(hir::QPath::Resolved( |
| None, |
| self.arena.alloc(hir::Path { |
| span: ident.span, |
| res: self.lower_res(res), |
| segments: arena_vec![self; hir::PathSegment::from_ident(ident)], |
| }), |
| )), |
| } |
| } |
| |
| fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation { |
| match *b { |
| BindingMode::ByValue(Mutability::Not) => hir::BindingAnnotation::Unannotated, |
| BindingMode::ByRef(Mutability::Not) => hir::BindingAnnotation::Ref, |
| BindingMode::ByValue(Mutability::Mut) => hir::BindingAnnotation::Mutable, |
| BindingMode::ByRef(Mutability::Mut) => hir::BindingAnnotation::RefMut, |
| } |
| } |
| |
| fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> { |
| self.pat_with_node_id_of(p, hir::PatKind::Wild) |
| } |
| |
| /// Construct a `Pat` with the `HirId` of `p.id` lowered. |
| fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> { |
| self.arena.alloc(hir::Pat { hir_id: self.lower_node_id(p.id), kind, span: p.span }) |
| } |
| |
| /// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern. |
| fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) { |
| self.diagnostic() |
| .struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx)) |
| .span_label(sp, &format!("can only be used once per {} pattern", ctx)) |
| .span_label(prev_sp, "previously used here") |
| .emit(); |
| } |
| |
| /// Used to ban the `..` pattern in places it shouldn't be semantically. |
| fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind<'hir> { |
| self.diagnostic() |
| .struct_span_err(sp, "`..` patterns are not allowed here") |
| .note("only allowed in tuple, tuple struct, and slice patterns") |
| .emit(); |
| |
| // We're not in a list context so `..` can be reasonably treated |
| // as `_` because it should always be valid and roughly matches the |
| // intent of `..` (notice that the rest of a single slot is that slot). |
| hir::PatKind::Wild |
| } |
| |
| fn lower_range_end(&mut self, e: &RangeEnd, has_end: bool) -> hir::RangeEnd { |
| match *e { |
| RangeEnd::Excluded if has_end => hir::RangeEnd::Excluded, |
| // No end; so `X..` behaves like `RangeFrom`. |
| RangeEnd::Excluded | RangeEnd::Included(_) => hir::RangeEnd::Included, |
| } |
| } |
| } |