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shorten common if let patterns to function calls #30266

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merged 1 commit into from
Dec 9, 2015
Merged

shorten common if let patterns to function calls #30266

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63 changes: 23 additions & 40 deletions src/librustc/middle/const_eval.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -515,6 +515,21 @@ pub enum EvalHint<'tcx> {
UncheckedExprNoHint,
}

impl<'tcx> EvalHint<'tcx> {
fn erase_hint(&self) -> EvalHint<'tcx> {
match *self {
ExprTypeChecked => ExprTypeChecked,
UncheckedExprHint(_) | UncheckedExprNoHint => UncheckedExprNoHint,
}
}
fn checked_or(&self, ty: Ty<'tcx>) -> EvalHint<'tcx> {
match *self {
ExprTypeChecked => ExprTypeChecked,
_ => UncheckedExprHint(ty),
}
}
}

#[derive(Copy, Clone, PartialEq, Debug)]
pub enum IntTy { I8, I16, I32, I64 }
#[derive(Copy, Clone, PartialEq, Debug)]
Expand Down Expand Up @@ -846,13 +861,7 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
}
hir::ExprBinary(op, ref a, ref b) => {
let b_ty = match op.node {
hir::BiShl | hir::BiShr => {
if let ExprTypeChecked = ty_hint {
ExprTypeChecked
} else {
UncheckedExprHint(tcx.types.usize)
}
}
hir::BiShl | hir::BiShr => ty_hint.checked_or(tcx.types.usize),
_ => ty_hint
};
match (try!(eval_const_expr_partial(tcx, &**a, ty_hint, fn_args)),
Expand Down Expand Up @@ -1072,11 +1081,7 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
try!(eval_const_expr_partial(tcx, const_expr, item_hint, fn_args))
}
hir::ExprCall(ref callee, ref args) => {
let sub_ty_hint = if let ExprTypeChecked = ty_hint {
ExprTypeChecked
} else {
UncheckedExprNoHint // we cannot reason about UncheckedExprHint here
};
let sub_ty_hint = ty_hint.erase_hint();
let callee_val = try!(eval_const_expr_partial(tcx, callee, sub_ty_hint, fn_args));
let (decl, block, constness) = try!(get_fn_def(tcx, e, callee_val));
match (ty_hint, constness) {
Expand Down Expand Up @@ -1109,9 +1114,7 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
debug!("const call({:?})", call_args);
try!(eval_const_expr_partial(tcx, &**result, ty_hint, Some(&call_args)))
},
hir::ExprLit(ref lit) => {
lit_to_const(&**lit, ety)
}
hir::ExprLit(ref lit) => lit_to_const(&**lit, ety),
hir::ExprBlock(ref block) => {
match block.expr {
Some(ref expr) => try!(eval_const_expr_partial(tcx, &**expr, ty_hint, fn_args)),
Expand All @@ -1124,17 +1127,9 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
if !tcx.sess.features.borrow().const_indexing {
signal!(e, IndexOpFeatureGated);
}
let arr_hint = if let ExprTypeChecked = ty_hint {
ExprTypeChecked
} else {
UncheckedExprNoHint
};
let arr_hint = ty_hint.erase_hint();
let arr = try!(eval_const_expr_partial(tcx, arr, arr_hint, fn_args));
let idx_hint = if let ExprTypeChecked = ty_hint {
ExprTypeChecked
} else {
UncheckedExprHint(tcx.types.usize)
};
let idx_hint = ty_hint.checked_or(tcx.types.usize);
let idx = match try!(eval_const_expr_partial(tcx, idx, idx_hint, fn_args)) {
Int(i) if i >= 0 => i as u64,
Int(_) => signal!(idx, IndexNegative),
Expand Down Expand Up @@ -1169,11 +1164,7 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
}
hir::ExprVec(ref v) => Array(e.id, v.len() as u64),
hir::ExprRepeat(_, ref n) => {
let len_hint = if let ExprTypeChecked = ty_hint {
ExprTypeChecked
} else {
UncheckedExprHint(tcx.types.usize)
};
let len_hint = ty_hint.checked_or(tcx.types.usize);
Repeat(
e.id,
match try!(eval_const_expr_partial(tcx, &**n, len_hint, fn_args)) {
Expand All @@ -1185,11 +1176,7 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
)
},
hir::ExprTupField(ref base, index) => {
let base_hint = if let ExprTypeChecked = ty_hint {
ExprTypeChecked
} else {
UncheckedExprNoHint
};
let base_hint = ty_hint.erase_hint();
if let Ok(c) = eval_const_expr_partial(tcx, base, base_hint, fn_args) {
if let Tuple(tup_id) = c {
if let hir::ExprTup(ref fields) = tcx.map.expect_expr(tup_id).node {
Expand All @@ -1209,12 +1196,8 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
}
}
hir::ExprField(ref base, field_name) => {
let base_hint = ty_hint.erase_hint();
// Get the base expression if it is a struct and it is constant
let base_hint = if let ExprTypeChecked = ty_hint {
ExprTypeChecked
} else {
UncheckedExprNoHint
};
if let Ok(c) = eval_const_expr_partial(tcx, base, base_hint, fn_args) {
if let Struct(struct_id) = c {
if let hir::ExprStruct(_, ref fields, _) = tcx.map.expect_expr(struct_id).node {
Expand Down