extract pattern lowering -> pat.rs

2 files changed, 256 insertions, 246 deletions

diff --git a/src/librustc_ast_lowering/lib.rs b/src/librustc_ast_lowering/lib.rs
index c4b99224369..658bcb26ecf 100644
--- a/src/librustc_ast_lowering/lib.rs
+++ b/src/librustc_ast_lowering/lib.rs
@@ -33,6 +33,7 @@
 //! in the HIR, especially for multiple identifiers.
 
 #![feature(array_value_iter)]
+#![feature(crate_visibility_modifier)]
 
 use rustc::arena::Arena;
 use rustc::dep_graph::DepGraph;
@@ -58,14 +59,13 @@ use rustc_session::config::nightly_options;
 use rustc_session::node_id::NodeMap;
 use rustc_session::Session;
 use rustc_span::hygiene::ExpnId;
-use rustc_span::source_map::{respan, DesugaringKind, ExpnData, ExpnKind, Spanned};
+use rustc_span::source_map::{respan, DesugaringKind, ExpnData, ExpnKind};
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
 use syntax::ast;
 use syntax::ast::*;
 use syntax::attr;
 use syntax::print::pprust;
-use syntax::ptr::P as AstP;
 use syntax::sess::ParseSess;
 use syntax::token::{self, Nonterminal, Token};
 use syntax::tokenstream::{TokenStream, TokenTree};
@@ -86,6 +86,7 @@ macro_rules! arena_vec {
 
 mod expr;
 mod item;
+mod pat;
 
 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
 
@@ -2636,250 +2637,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.expr_block(block, AttrVec::new())
     }
 
-    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(
-                self.lower_expr(e1),
-                self.lower_expr(e2),
-                self.lower_range_end(end),
-            ),
-            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: &[AstP<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 $ident @)? ..` (`slice`),
-    /// this is interpreted as a sub-slice pattern semantically.
-    /// Patterns that follow, which are not like `slice` -- or an error occurs, are in `after`.
-    fn lower_pat_slice(&mut self, pats: &[AstP<Pat>]) -> hir::PatKind<'hir> {
-        let mut before = Vec::new();
-        let mut after = Vec::new();
-        let mut slice = None;
-        let mut prev_rest_span = None;
-
-        let mut iter = pats.iter();
-        // Lower all the patterns until the first occurence of a sub-slice pattern.
-        for pat in iter.by_ref() {
-            match pat.kind {
-                // Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
-                PatKind::Rest => {
-                    prev_rest_span = Some(pat.span);
-                    slice = Some(self.pat_wild_with_node_id_of(pat));
-                    break;
-                }
-                // Found a sub-slice pattern `$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 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) -> hir::RangeEnd {
-        match *e {
-            RangeEnd::Included(_) => hir::RangeEnd::Included,
-            RangeEnd::Excluded => hir::RangeEnd::Excluded,
-        }
-    }
-
     fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
         self.with_new_scopes(|this| hir::AnonConst {
             hir_id: this.lower_node_id(c.id),
diff --git a/src/librustc_ast_lowering/pat.rs b/src/librustc_ast_lowering/pat.rs
new file mode 100644
index 00000000000..3a3ffd7560b
--- /dev/null
+++ b/src/librustc_ast_lowering/pat.rs
@@ -0,0 +1,253 @@
+use super::{ImplTraitContext, LoweringContext, ParamMode};
+
+use rustc::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(
+                self.lower_expr(e1),
+                self.lower_expr(e2),
+                self.lower_range_end(end),
+            ),
+            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 $ident @)? ..` (`slice`),
+    /// this is interpreted as a sub-slice pattern semantically.
+    /// Patterns that follow, which are not like `slice` -- or an error occurs, are in `after`.
+    fn lower_pat_slice(&mut self, pats: &[P<Pat>]) -> hir::PatKind<'hir> {
+        let mut before = Vec::new();
+        let mut after = Vec::new();
+        let mut slice = None;
+        let mut prev_rest_span = None;
+
+        let mut iter = pats.iter();
+        // Lower all the patterns until the first occurence of a sub-slice pattern.
+        for pat in iter.by_ref() {
+            match pat.kind {
+                // Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
+                PatKind::Rest => {
+                    prev_rest_span = Some(pat.span);
+                    slice = Some(self.pat_wild_with_node_id_of(pat));
+                    break;
+                }
+                // Found a sub-slice pattern `$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 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) -> hir::RangeEnd {
+        match *e {
+            RangeEnd::Included(_) => hir::RangeEnd::Included,
+            RangeEnd::Excluded => hir::RangeEnd::Excluded,
+        }
+    }
+}