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Get rid of token passing
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@oli-obk
oli-obk committed Aug 31, 2018
1 parent b68bb63 commit 2839f4f
Showing 1 changed file with 35 additions and 55 deletions.
90 changes: 35 additions & 55 deletions src/librustc_mir/transform/qualify_min_const_fn.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,17 +5,7 @@ use rustc::ty::{self, Predicate, TyCtxt};
use std::borrow::Cow;
use syntax_pos::Span;

mod helper {
pub struct IsMinConstFn(());
/// This should only ever be used *once* and then passed around as a token.
pub fn ensure_that_you_really_intended_to_create_an_instance_of_this() -> IsMinConstFn {
IsMinConstFn(())
}
}

use self::helper::*;

type McfResult = Result<IsMinConstFn, (Span, Cow<'static, str>)>;
type McfResult = Result<(), (Span, Cow<'static, str>)>;

pub fn is_min_const_fn(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
Expand Down Expand Up @@ -74,39 +64,35 @@ pub fn is_min_const_fn(
}
}

let mut token = ensure_that_you_really_intended_to_create_an_instance_of_this();

for local in mir.vars_iter() {
return Err((
mir.local_decls[local].source_info.span,
"local variables in const fn are unstable".into(),
));
}
for local in &mir.local_decls {
token = check_ty(tcx, local.ty, local.source_info.span, token)?;
check_ty(tcx, local.ty, local.source_info.span)?;
}
// impl trait is gone in MIR, so check the return type manually
token = check_ty(
check_ty(
tcx,
tcx.fn_sig(def_id).output().skip_binder(),
mir.local_decls.iter().next().unwrap().source_info.span,
token,
)?;

for bb in mir.basic_blocks() {
token = check_terminator(tcx, mir, bb.terminator(), token)?;
check_terminator(tcx, mir, bb.terminator())?;
for stmt in &bb.statements {
token = check_statement(tcx, mir, stmt, token)?;
check_statement(tcx, mir, stmt)?;
}
}
Ok(token)
Ok(())
}

fn check_ty(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
ty: ty::Ty<'tcx>,
span: Span,
token: IsMinConstFn,
) -> McfResult {
for ty in ty.walk() {
match ty.sty {
Expand Down Expand Up @@ -146,22 +132,21 @@ fn check_ty(
_ => {}
}
}
Ok(token)
Ok(())
}

fn check_rvalue(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &'a Mir<'tcx>,
rvalue: &Rvalue<'tcx>,
span: Span,
token: IsMinConstFn,
) -> McfResult {
match rvalue {
Rvalue::Repeat(operand, _) | Rvalue::Use(operand) => {
check_operand(tcx, mir, operand, span, token)
check_operand(tcx, mir, operand, span)
}
Rvalue::Len(place) | Rvalue::Discriminant(place) | Rvalue::Ref(_, _, place) => {
check_place(tcx, mir, place, span, token, PlaceMode::Read)
check_place(tcx, mir, place, span, PlaceMode::Read)
}
Rvalue::Cast(_, operand, cast_ty) => {
use rustc::ty::cast::CastTy;
Expand All @@ -175,16 +160,16 @@ fn check_rvalue(
(CastTy::RPtr(_), CastTy::Float) => bug!(),
(CastTy::RPtr(_), CastTy::Int(_)) => bug!(),
(CastTy::Ptr(_), CastTy::RPtr(_)) => bug!(),
_ => check_operand(tcx, mir, operand, span, token),
_ => check_operand(tcx, mir, operand, span),
}
}
// binops are fine on integers
Rvalue::BinaryOp(_, lhs, rhs) | Rvalue::CheckedBinaryOp(_, lhs, rhs) => {
let token = check_operand(tcx, mir, lhs, span, token)?;
let token = check_operand(tcx, mir, rhs, span, token)?;
check_operand(tcx, mir, lhs, span)?;
check_operand(tcx, mir, rhs, span)?;
let ty = lhs.ty(mir, tcx);
if ty.is_integral() || ty.is_bool() || ty.is_char() {
Ok(token)
Ok(())
} else {
Err((
span,
Expand All @@ -193,11 +178,11 @@ fn check_rvalue(
}
}
// checked by regular const fn checks
Rvalue::NullaryOp(..) => Ok(token),
Rvalue::NullaryOp(..) => Ok(()),
Rvalue::UnaryOp(_, operand) => {
let ty = operand.ty(mir, tcx);
if ty.is_integral() || ty.is_bool() {
check_operand(tcx, mir, operand, span, token)
check_operand(tcx, mir, operand, span)
} else {
Err((
span,
Expand All @@ -206,11 +191,10 @@ fn check_rvalue(
}
}
Rvalue::Aggregate(_, operands) => {
let mut token = token;
for operand in operands {
token = check_operand(tcx, mir, operand, span, token)?;
check_operand(tcx, mir, operand, span)?;
}
Ok(token)
Ok(())
}
}
}
Expand All @@ -224,19 +208,18 @@ fn check_statement(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &'a Mir<'tcx>,
statement: &Statement<'tcx>,
token: IsMinConstFn,
) -> McfResult {
let span = statement.source_info.span;
match &statement.kind {
StatementKind::Assign(place, rval) => {
let token = check_place(tcx, mir, place, span, token, PlaceMode::Assign)?;
check_rvalue(tcx, mir, rval, span, token)
check_place(tcx, mir, place, span, PlaceMode::Assign)?;
check_rvalue(tcx, mir, rval, span)
}

StatementKind::ReadForMatch(_) => Err((span, "match in const fn is unstable".into())),

// just an assignment
StatementKind::SetDiscriminant { .. } => Ok(token),
StatementKind::SetDiscriminant { .. } => Ok(()),

| StatementKind::InlineAsm { .. } => {
Err((span, "cannot use inline assembly in const fn".into()))
Expand All @@ -248,7 +231,7 @@ fn check_statement(
| StatementKind::Validate(..)
| StatementKind::EndRegion(_)
| StatementKind::UserAssertTy(..)
| StatementKind::Nop => Ok(token),
| StatementKind::Nop => Ok(()),
}
}

Expand All @@ -257,13 +240,12 @@ fn check_operand(
mir: &'a Mir<'tcx>,
operand: &Operand<'tcx>,
span: Span,
token: IsMinConstFn,
) -> McfResult {
match operand {
Operand::Move(place) | Operand::Copy(place) => {
check_place(tcx, mir, place, span, token, PlaceMode::Read)
check_place(tcx, mir, place, span, PlaceMode::Read)
}
Operand::Constant(_) => Ok(token),
Operand::Constant(_) => Ok(()),
}
}

Expand All @@ -272,26 +254,25 @@ fn check_place(
mir: &'a Mir<'tcx>,
place: &Place<'tcx>,
span: Span,
token: IsMinConstFn,
mode: PlaceMode,
) -> McfResult {
match place {
Place::Local(l) => match mode {
PlaceMode::Assign => match mir.local_kind(*l) {
LocalKind::Temp | LocalKind::ReturnPointer => Ok(token),
LocalKind::Temp | LocalKind::ReturnPointer => Ok(()),
LocalKind::Arg | LocalKind::Var => {
Err((span, "assignments in const fn are unstable".into()))
}
},
PlaceMode::Read => Ok(token),
PlaceMode::Read => Ok(()),
},
// promoteds are always fine, they are essentially constants
Place::Promoted(_) => Ok(token),
Place::Promoted(_) => Ok(()),
Place::Static(_) => Err((span, "cannot access `static` items in const fn".into())),
Place::Projection(proj) => {
match proj.elem {
| ProjectionElem::Deref | ProjectionElem::Field(..) | ProjectionElem::Index(_) => {
check_place(tcx, mir, &proj.base, span, token, mode)
check_place(tcx, mir, &proj.base, span, mode)
}
// slice patterns are unstable
| ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
Expand All @@ -309,20 +290,19 @@ fn check_terminator(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
mir: &'a Mir<'tcx>,
terminator: &Terminator<'tcx>,
token: IsMinConstFn,
) -> McfResult {
let span = terminator.source_info.span;
match &terminator.kind {
| TerminatorKind::Goto { .. }
| TerminatorKind::Return
| TerminatorKind::Resume => Ok(token),
| TerminatorKind::Resume => Ok(()),

TerminatorKind::Drop { location, .. } => {
check_place(tcx, mir, location, span, token, PlaceMode::Read)
check_place(tcx, mir, location, span, PlaceMode::Read)
}
TerminatorKind::DropAndReplace { location, value, .. } => {
let token = check_place(tcx, mir, location, span, token, PlaceMode::Read)?;
check_operand(tcx, mir, value, span, token)
check_place(tcx, mir, location, span, PlaceMode::Read)?;
check_operand(tcx, mir, value, span)
},
TerminatorKind::SwitchInt { .. } => Err((
span,
Expand All @@ -344,12 +324,12 @@ fn check_terminator(
let fn_ty = func.ty(mir, tcx);
if let ty::FnDef(def_id, _) = fn_ty.sty {
if tcx.is_min_const_fn(def_id) {
let mut token = check_operand(tcx, mir, func, span, token)?;
check_operand(tcx, mir, func, span)?;

for arg in args {
token = check_operand(tcx, mir, arg, span, token)?;
check_operand(tcx, mir, arg, span)?;
}
Ok(token)
Ok(())
} else {
Err((
span,
Expand All @@ -367,7 +347,7 @@ fn check_terminator(
msg: _,
target: _,
cleanup: _,
} => check_operand(tcx, mir, cond, span, token),
} => check_operand(tcx, mir, cond, span),

| TerminatorKind::FalseEdges { .. } | TerminatorKind::FalseUnwind { .. } => span_bug!(
terminator.source_info.span,
Expand Down

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