fix handling of blocks with CoerceMany
This commit is contained in:
Niko Matsakis
parent
f83706454f
commit
d448329849
@ -926,7 +926,7 @@ pub struct CoerceMany<'gcx, 'tcx, 'exprs, E>
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/// The type of a `CoerceMany` that is storing up the expressions into
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/// a buffer. We use this in `check/mod.rs` for things like `break`.
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pub type DynamicCoerceMany<'gcx, 'tcx> = CoerceMany<'gcx, 'tcx, 'static, hir::Expr>;
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pub type DynamicCoerceMany<'gcx, 'tcx> = CoerceMany<'gcx, 'tcx, 'gcx, P<hir::Expr>>;
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#[derive(Clone)] // (*)
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enum Expressions<'gcx, 'exprs, E>
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@ -86,6 +86,7 @@ use dep_graph::DepNode;
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use fmt_macros::{Parser, Piece, Position};
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use hir::def::{Def, CtorKind};
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use hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
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use rustc_back::slice::ref_slice;
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use rustc::infer::{self, InferCtxt, InferOk, RegionVariableOrigin, TypeTrace};
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use rustc::infer::type_variable::{self, TypeVariableOrigin};
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use rustc::ty::subst::{Kind, Subst, Substs};
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@ -4108,102 +4109,64 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
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replace(&mut *fcx_ps, unsafety_state)
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};
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let mut ty = if blk.targeted_by_break {
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let unified = self.next_ty_var(TypeVariableOrigin::TypeInference(blk.span));
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let coerce_to = expected.only_has_type(self).unwrap_or(unified);
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let ctxt = BreakableCtxt {
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unified: unified,
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coerce_to: coerce_to,
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break_exprs: vec![],
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may_break: false,
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};
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let (mut ctxt, (e_ty, cause)) = self.with_breakable_ctxt(blk.id, ctxt, || {
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for s in &blk.stmts {
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self.check_stmt(s);
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}
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let coerce_to = {
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let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
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enclosing_breakables.find_breakable(blk.id).coerce_to
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};
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let e_ty;
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let cause;
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match blk.expr {
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Some(ref e) => {
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e_ty = self.check_expr_with_hint(e, coerce_to);
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cause = self.misc(e.span);
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},
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None => {
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e_ty = if self.diverges.get().always() {
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self.tcx.types.never
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} else {
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self.tcx.mk_nil()
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};
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cause = self.misc(blk.span);
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}
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};
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(e_ty, cause)
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});
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if let ExpectHasType(ety) = expected {
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if let Some(ref e) = blk.expr {
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let result = if !ctxt.may_break {
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self.try_coerce(e, e_ty, ctxt.coerce_to)
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} else {
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self.try_find_coercion_lub(&cause, || ctxt.break_exprs.iter().cloned(),
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ctxt.unified, e, e_ty)
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};
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match result {
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Ok(ty) => ctxt.unified = ty,
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Err(err) =>
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self.report_mismatched_types(&cause, ctxt.unified, e_ty, err).emit(),
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}
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} else if self.diverges.get().always() {
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// No tail expression and the body diverges; ignore
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// the expected type, and keep `!` as the type of the
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// block.
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} else {
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self.check_block_no_expr(blk, self.tcx.mk_nil(), e_ty);
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};
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ctxt.unified
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// In some cases, blocks have just one exit, but other blocks
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// can be targeted by multiple breaks. This cannot happen in
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// normal Rust syntax today, but it can happen when we desugar
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// a `do catch { ... }` expression.
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//
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// Example 1:
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//
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// 'a: { if true { break 'a Err(()); } Ok(()) }
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//
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// Here we would wind up with two coercions, one from
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// `Err(())` and the other from the tail expression
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// `Ok(())`. If the tail expression is omitted, that's a
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// "forced unit" -- unless the block diverges, in which
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// case we can ignore the tail expression (e.g., `'a: {
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// break 'a 22; }` would not force the type of the block
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// to be `()`).
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let tail_expr = blk.expr.as_ref();
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let coerce_to_ty = expected.coercion_target_type(self, blk.span);
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let coerce = if blk.targeted_by_break {
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CoerceMany::new(coerce_to_ty)
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} else {
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let tail_expr: &[P<hir::Expr>] = match tail_expr {
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Some(e) => ref_slice(e),
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None => &[],
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};
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CoerceMany::with_coercion_sites(coerce_to_ty, tail_expr)
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};
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let ctxt = BreakableCtxt {
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coerce: Some(coerce),
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may_break: false,
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};
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let (ctxt, ()) = self.with_breakable_ctxt(blk.id, ctxt, || {
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for s in &blk.stmts {
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self.check_stmt(s);
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}
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let mut ty = match blk.expr {
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Some(ref e) => self.check_expr_with_expectation(e, expected),
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None => if self.diverges.get().always() {
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self.tcx.types.never
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} else {
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self.tcx.mk_nil()
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},
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};
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// check the tail expression **without** holding the
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// `enclosing_breakables` lock below.
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let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
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if let ExpectHasType(ety) = expected {
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if let Some(ref e) = blk.expr {
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// Coerce the tail expression to the right type.
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self.demand_coerce(e, ty, ety);
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// We already applied the type (and potentially errored),
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// use the expected type to avoid further errors out.
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ty = ety;
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} else if self.diverges.get().always() {
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// No tail expression and the body diverges; ignore
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// the expected type, and keep `!` as the type of the
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// block.
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} else {
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self.check_block_no_expr(blk, ty, ety);
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// We already applied the type (and potentially errored),
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// use the expected type to avoid further errors out.
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ty = ety;
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}
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let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
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let mut ctxt = enclosing_breakables.find_breakable(blk.id);
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let mut coerce = ctxt.coerce.as_mut().unwrap();
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if let Some(tail_expr_ty) = tail_expr_ty {
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let tail_expr = tail_expr.unwrap();
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coerce.coerce(self,
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&self.misc(tail_expr.span),
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tail_expr,
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tail_expr_ty,
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self.diverges.get()); // TODO
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} else if !self.diverges.get().always() {
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coerce.coerce_forced_unit(self, &self.misc(blk.span));
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}
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ty
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};
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});
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let mut ty = ctxt.coerce.unwrap().complete(self);
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if self.has_errors.get() || ty.references_error() {
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ty = self.tcx.types.err
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