1 files changed, 122 insertions, 0 deletions
diff --git a/compiler/rustc_ast_lowering/src/block.rs b/compiler/rustc_ast_lowering/src/block.rs
new file mode 100644
index 000000000..7cbfe143b
--- /dev/null
+++ b/compiler/rustc_ast_lowering/src/block.rs
@@ -0,0 +1,122 @@
+use crate::{ImplTraitContext, ImplTraitPosition, LoweringContext};
+use rustc_ast::{Block, BlockCheckMode, Local, LocalKind, Stmt, StmtKind};
+use rustc_hir as hir;
+use rustc_session::parse::feature_err;
+use rustc_span::sym;
+
+use smallvec::SmallVec;
+
+impl<'a, 'hir> LoweringContext<'a, 'hir> {
+    pub(super) fn lower_block(
+        &mut self,
+        b: &Block,
+        targeted_by_break: bool,
+    ) -> &'hir hir::Block<'hir> {
+        self.arena.alloc(self.lower_block_noalloc(b, targeted_by_break))
+    }
+
+    pub(super) fn lower_block_noalloc(
+        &mut self,
+        b: &Block,
+        targeted_by_break: bool,
+    ) -> hir::Block<'hir> {
+        let (stmts, expr) = self.lower_stmts(&b.stmts);
+        let rules = self.lower_block_check_mode(&b.rules);
+        let hir_id = self.lower_node_id(b.id);
+        hir::Block { hir_id, stmts, expr, rules, span: self.lower_span(b.span), targeted_by_break }
+    }
+
+    fn lower_stmts(
+        &mut self,
+        mut ast_stmts: &[Stmt],
+    ) -> (&'hir [hir::Stmt<'hir>], Option<&'hir hir::Expr<'hir>>) {
+        let mut stmts = SmallVec::<[hir::Stmt<'hir>; 8]>::new();
+        let mut expr = None;
+        while let [s, tail @ ..] = ast_stmts {
+            match s.kind {
+                StmtKind::Local(ref local) => {
+                    let hir_id = self.lower_node_id(s.id);
+                    let local = self.lower_local(local);
+                    self.alias_attrs(hir_id, local.hir_id);
+                    let kind = hir::StmtKind::Local(local);
+                    let span = self.lower_span(s.span);
+                    stmts.push(hir::Stmt { hir_id, kind, span });
+                }
+                StmtKind::Item(ref it) => {
+                    stmts.extend(self.lower_item_ref(it).into_iter().enumerate().map(
+                        |(i, item_id)| {
+                            let hir_id = match i {
+                                0 => self.lower_node_id(s.id),
+                                _ => self.next_id(),
+                            };
+                            let kind = hir::StmtKind::Item(item_id);
+                            let span = self.lower_span(s.span);
+                            hir::Stmt { hir_id, kind, span }
+                        },
+                    ));
+                }
+                StmtKind::Expr(ref e) => {
+                    let e = self.lower_expr(e);
+                    if tail.is_empty() {
+                        expr = Some(e);
+                    } else {
+                        let hir_id = self.lower_node_id(s.id);
+                        self.alias_attrs(hir_id, e.hir_id);
+                        let kind = hir::StmtKind::Expr(e);
+                        let span = self.lower_span(s.span);
+                        stmts.push(hir::Stmt { hir_id, kind, span });
+                    }
+                }
+                StmtKind::Semi(ref e) => {
+                    let e = self.lower_expr(e);
+                    let hir_id = self.lower_node_id(s.id);
+                    self.alias_attrs(hir_id, e.hir_id);
+                    let kind = hir::StmtKind::Semi(e);
+                    let span = self.lower_span(s.span);
+                    stmts.push(hir::Stmt { hir_id, kind, span });
+                }
+                StmtKind::Empty => {}
+                StmtKind::MacCall(..) => panic!("shouldn't exist here"),
+            }
+            ast_stmts = &ast_stmts[1..];
+        }
+        (self.arena.alloc_from_iter(stmts), expr)
+    }
+
+    fn lower_local(&mut self, l: &Local) -> &'hir hir::Local<'hir> {
+        let ty = l
+            .ty
+            .as_ref()
+            .map(|t| self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::Variable)));
+        let init = l.kind.init().map(|init| self.lower_expr(init));
+        let hir_id = self.lower_node_id(l.id);
+        let pat = self.lower_pat(&l.pat);
+        let els = if let LocalKind::InitElse(_, els) = &l.kind {
+            if !self.tcx.features().let_else {
+                feature_err(
+                    &self.tcx.sess.parse_sess,
+                    sym::let_else,
+                    l.span,
+                    "`let...else` statements are unstable",
+                )
+                .emit();
+            }
+            Some(self.lower_block(els, false))
+        } else {
+            None
+        };
+        let span = self.lower_span(l.span);
+        let source = hir::LocalSource::Normal;
+        self.lower_attrs(hir_id, &l.attrs);
+        self.arena.alloc(hir::Local { hir_id, ty, pat, init, els, span, source })
+    }
+
+    fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
+        match *b {
+            BlockCheckMode::Default => hir::BlockCheckMode::DefaultBlock,
+            BlockCheckMode::Unsafe(u) => {
+                hir::BlockCheckMode::UnsafeBlock(self.lower_unsafe_source(u))
+            }
+        }
+    }
+}