1 files changed, 160 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/check/gather_locals.rs b/compiler/rustc_typeck/src/check/gather_locals.rs
new file mode 100644
index 000000000..8f34a970f
--- /dev/null
+++ b/compiler/rustc_typeck/src/check/gather_locals.rs
@@ -0,0 +1,160 @@
+use crate::check::{FnCtxt, LocalTy, UserType};
+use rustc_hir as hir;
+use rustc_hir::intravisit::{self, Visitor};
+use rustc_hir::PatKind;
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_middle::ty::Ty;
+use rustc_span::Span;
+use rustc_trait_selection::traits;
+
+/// A declaration is an abstraction of [hir::Local] and [hir::Let].
+///
+/// It must have a hir_id, as this is how we connect gather_locals to the check functions.
+pub(super) struct Declaration<'a> {
+    pub hir_id: hir::HirId,
+    pub pat: &'a hir::Pat<'a>,
+    pub ty: Option<&'a hir::Ty<'a>>,
+    pub span: Span,
+    pub init: Option<&'a hir::Expr<'a>>,
+    pub els: Option<&'a hir::Block<'a>>,
+}
+
+impl<'a> From<&'a hir::Local<'a>> for Declaration<'a> {
+    fn from(local: &'a hir::Local<'a>) -> Self {
+        let hir::Local { hir_id, pat, ty, span, init, els, source: _ } = *local;
+        Declaration { hir_id, pat, ty, span, init, els }
+    }
+}
+
+impl<'a> From<&'a hir::Let<'a>> for Declaration<'a> {
+    fn from(let_expr: &'a hir::Let<'a>) -> Self {
+        let hir::Let { hir_id, pat, ty, span, init } = *let_expr;
+        Declaration { hir_id, pat, ty, span, init: Some(init), els: None }
+    }
+}
+
+pub(super) struct GatherLocalsVisitor<'a, 'tcx> {
+    fcx: &'a FnCtxt<'a, 'tcx>,
+    // parameters are special cases of patterns, but we want to handle them as
+    // *distinct* cases. so track when we are hitting a pattern *within* an fn
+    // parameter.
+    outermost_fn_param_pat: Option<Span>,
+}
+
+impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
+    pub(super) fn new(fcx: &'a FnCtxt<'a, 'tcx>) -> Self {
+        Self { fcx, outermost_fn_param_pat: None }
+    }
+
+    fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
+        match ty_opt {
+            None => {
+                // Infer the variable's type.
+                let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
+                    kind: TypeVariableOriginKind::TypeInference,
+                    span,
+                });
+                self.fcx
+                    .locals
+                    .borrow_mut()
+                    .insert(nid, LocalTy { decl_ty: var_ty, revealed_ty: var_ty });
+                var_ty
+            }
+            Some(typ) => {
+                // Take type that the user specified.
+                self.fcx.locals.borrow_mut().insert(nid, typ);
+                typ.revealed_ty
+            }
+        }
+    }
+
+    /// Allocates a [LocalTy] for a declaration, which may have a type annotation. If it does have
+    /// a type annotation, then the LocalTy stored will be the resolved type. This may be found
+    /// again during type checking by querying [FnCtxt::local_ty] for the same hir_id.
+    fn declare(&mut self, decl: Declaration<'tcx>) {
+        let local_ty = match decl.ty {
+            Some(ref ty) => {
+                let o_ty = self.fcx.to_ty(&ty);
+
+                let c_ty = self.fcx.inh.infcx.canonicalize_user_type_annotation(UserType::Ty(o_ty));
+                debug!("visit_local: ty.hir_id={:?} o_ty={:?} c_ty={:?}", ty.hir_id, o_ty, c_ty);
+                self.fcx
+                    .typeck_results
+                    .borrow_mut()
+                    .user_provided_types_mut()
+                    .insert(ty.hir_id, c_ty);
+
+                Some(LocalTy { decl_ty: o_ty, revealed_ty: o_ty })
+            }
+            None => None,
+        };
+        self.assign(decl.span, decl.hir_id, local_ty);
+
+        debug!(
+            "local variable {:?} is assigned type {}",
+            decl.pat,
+            self.fcx.ty_to_string(self.fcx.locals.borrow().get(&decl.hir_id).unwrap().decl_ty)
+        );
+    }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
+    // Add explicitly-declared locals.
+    fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
+        self.declare(local.into());
+        intravisit::walk_local(self, local)
+    }
+
+    fn visit_let_expr(&mut self, let_expr: &'tcx hir::Let<'tcx>) {
+        self.declare(let_expr.into());
+        intravisit::walk_let_expr(self, let_expr);
+    }
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        let old_outermost_fn_param_pat = self.outermost_fn_param_pat.replace(param.ty_span);
+        intravisit::walk_param(self, param);
+        self.outermost_fn_param_pat = old_outermost_fn_param_pat;
+    }
+
+    // Add pattern bindings.
+    fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
+        if let PatKind::Binding(_, _, ident, _) = p.kind {
+            let var_ty = self.assign(p.span, p.hir_id, None);
+
+            if let Some(ty_span) = self.outermost_fn_param_pat {
+                if !self.fcx.tcx.features().unsized_fn_params {
+                    self.fcx.require_type_is_sized(
+                        var_ty,
+                        p.span,
+                        traits::SizedArgumentType(Some(ty_span)),
+                    );
+                }
+            } else {
+                if !self.fcx.tcx.features().unsized_locals {
+                    self.fcx.require_type_is_sized(var_ty, p.span, traits::VariableType(p.hir_id));
+                }
+            }
+
+            debug!(
+                "pattern binding {} is assigned to {} with type {:?}",
+                ident,
+                self.fcx.ty_to_string(self.fcx.locals.borrow().get(&p.hir_id).unwrap().decl_ty),
+                var_ty
+            );
+        }
+        let old_outermost_fn_param_pat = self.outermost_fn_param_pat.take();
+        intravisit::walk_pat(self, p);
+        self.outermost_fn_param_pat = old_outermost_fn_param_pat;
+    }
+
+    // Don't descend into the bodies of nested closures.
+    fn visit_fn(
+        &mut self,
+        _: intravisit::FnKind<'tcx>,
+        _: &'tcx hir::FnDecl<'tcx>,
+        _: hir::BodyId,
+        _: Span,
+        _: hir::HirId,
+    ) {
+    }
+}