//! }])
//! ~~~
//!
-//! For `C1 {x}` and `C1 {x}` ,
+//! For `C1 {x}` and `C1 {x}`,
//!
//! ~~~text
//! EnumMatching(1, <ast::Variant for C1>,
//! For `C0(a)` and `C1 {x}` ,
//!
//! ~~~text
-//! EnumNonMatching(~[(0, <ast::Variant for B0>,
-//! ~[(<span of int>, None, <expr for &a>)]),
-//! (1, <ast::Variant for B1>,
-//! ~[(<span of x>, Some(<ident of x>),
-//! <expr for &other.x>)])])
+//! EnumNonMatchingCollapsed(
+//! ~[<ident of self>, <ident of __arg_1>],
+//! &[<ast::Variant for C0>, <ast::Variant for C1>],
+//! &[<ident for self index value>, <ident of __arg_1 index value>])
//! ~~~
//!
-//! (and vice versa, but with the order of the outermost list flipped.)
+//! It is the same for when the arguments are flipped to `C1 {x}` and
+//! `C0(a)`; the only difference is what the values of the identifiers
+//! <ident for self index value> and <ident of __arg_1 index value> will
+//! be in the generated code.
+//!
+//! `EnumNonMatchingCollapsed` deliberately provides far less information
+//! than is generally available for a given pair of variants; see #15375
+//! for discussion.
//!
//! ## Static
//!
//! (<ident of C1>, <span of C1>,
//! Named(~[(<ident of x>, <span of x>)]))])
//! ~~~
-//!
use std::cell::RefCell;
use std::gc::{Gc, GC};
#[deriving(PartialEq, Eq)]
pub enum HandleNonMatchingEnums {
- NonMatchesCollapse, // handle all non-matches via one `_ => ..` clause
- NonMatchesExplode, // handle via n^k cases for n variants and k self-args
- NonMatchHandlingIrrelevant, // cannot encounter two enums of Self type
+ /// handle all non-matches via one `_ => ..` clause
+ NonMatchesCollapse,
+
+ /// handle all non-matches via one `_ => ..` clause that has
+ /// access to a tuple of tags indicating each variant index.
+ NonMatchesCollapseWithTags,
+
+ /// handle via n^k cases for n variants and k self-args
+ NonMatchesExplode,
+
+ /// cannot encounter two enums of Self type
+ NonMatchHandlingIrrelevant,
}
pub struct MethodDef<'a> {
EnumNonMatching(&'a [(uint, P<ast::Variant>,
Vec<(Span, Option<Ident>, Gc<Expr>)>)]),
+ /**
+ non-matching variants of the enum, but with all state hidden from
+ the consequent code. The first component holds Idents for all of
+ the Self arguments; the second component is a slice of all of the
+ variants for the enum itself, and the third component is a list of
+ Idents bound to the variant index values for each of the actual
+ input Self arguments.
+ */
+ EnumNonMatchingCollapsed(Vec<Ident>, &'a [Gc<ast::Variant>], &'a [Ident]),
+
/// A static method where Self is a struct.
StaticStruct(&'a ast::StructDef, StaticFields),
/// A static method where Self is an enum.
|&mut ExtCtxt, Span, &Substructure|: 'a -> Gc<Expr>;
/**
-Deal with non-matching enum variants, the arguments are a list
-representing each variant: (variant index, ast::Variant instance,
-[variant fields]), and a list of the nonself args of the type
+Deal with non-matching enum variants. The tuple is a list of
+identifiers (one for each Self argument, which could be any of the
+variants since they have been collapsed together) and the identifiers
+holding the variant index value for each of the Self arguments. The
+last argument is all the non-Self args of the method being derived.
*/
-pub type EnumNonMatchFunc<'a> =
+pub type EnumNonMatchCollapsedFunc<'a> =
|&mut ExtCtxt,
Span,
- &[(uint, P<ast::Variant>, Vec<(Span, Option<Ident>, Gc<Expr>)>)],
+ (&[Ident], &[Ident]),
&[Gc<Expr>]|: 'a
-> Gc<Expr>;
}
}
+fn variant_to_pat(cx: &mut ExtCtxt, sp: Span, variant: &ast::Variant)
+ -> Gc<ast::Pat> {
+ let ident = cx.path_ident(sp, variant.node.name);
+ cx.pat(sp, match variant.node.kind {
+ ast::TupleVariantKind(..) => ast::PatEnum(ident, None),
+ ast::StructVariantKind(..) => ast::PatStruct(ident, Vec::new(), true),
+ })
+}
+
impl<'a> MethodDef<'a> {
fn call_substructure_method(&self,
cx: &mut ExtCtxt,
~~~
#[deriving(PartialEq)]
enum A {
- A1
+ A1,
A2(int)
}
- // is equivalent to (with on_nonmatching == NonMatchesExplode)
+ // is equivalent to
impl PartialEq for A {
- fn eq(&self, __arg_1: &A) {
- match *self {
- A1 => match *__arg_1 {
- A1 => true
- A2(ref __arg_1_1) => false
- },
- A2(self_1) => match *__arg_1 {
- A1 => false,
- A2(ref __arg_1_1) => self_1.eq(__arg_1_1)
+ fn eq(&self, __arg_1: &A) -> ::bool {
+ match (&*self, &*__arg_1) {
+ (&A1, &A1) => true,
+ (&A2(ref __self_0),
+ &A2(ref __arg_1_0)) => (*__self_0).eq(&(*__arg_1_0)),
+ _ => {
+ let __self_vi = match *self { A1(..) => 0u, A2(..) => 1u };
+ let __arg_1_vi = match *__arg_1 { A1(..) => 0u, A2(..) => 1u };
+ false
}
}
}
}
~~~
+
+ (Of course `__self_vi` and `__arg_1_vi` are unused for
+ `PartialEq`, and those subcomputations will hopefully be removed
+ as their results are unused. The point of `__self_vi` and
+ `__arg_1_vi` is for `PartialOrd`; see #15503.)
*/
fn expand_enum_method_body(&self,
cx: &mut ExtCtxt,
nonself_args: &[Gc<Expr>])
-> Gc<Expr> {
let mut matches = Vec::new();
- self.build_enum_match(cx, trait_, enum_def, type_ident,
- self_args, nonself_args,
- None, &mut matches, 0)
+ match self.on_nonmatching {
+ NonMatchesCollapseWithTags =>
+ self.build_enum_match_tuple(
+ cx, trait_, enum_def, type_ident, self_args, nonself_args),
+ NonMatchesCollapse | NonMatchesExplode | NonMatchHandlingIrrelevant =>
+ self.build_enum_match(
+ cx, trait_, enum_def, type_ident, self_args, nonself_args,
+ None, &mut matches, 0),
+ }
}
let mut arms = Vec::new();
+ assert!(self.on_nonmatching == NonMatchesCollapse ||
+ self.on_nonmatching == NonMatchesExplode ||
+ self.on_nonmatching == NonMatchHandlingIrrelevant);
+
// the code for nonmatching variants only matters when
// we've seen at least one other variant already
assert!(match_count == 0 ||
}
}
+ /**
+ Creates a match for a tuple of all `self_args`, where either all
+ variants match, or it falls into a catch-all for when one variant
+ does not match.
+
+ There are N + 1 cases because is a case for each of the N
+ variants where all of the variants match, and one catch-all for
+ when one does not match.
+
+ The catch-all handler is provided access the variant index values
+ for each of the self-args, carried in precomputed variables. (Nota
+ bene: the variant index values are not necessarily the
+ discriminant values. See issue #15523.)
+
+ ~~~text
+ match (this, that, ...) {
+ (Variant1, Variant1, Variant1) => ... // delegate Matching on Variant1
+ (Variant2, Variant2, Variant2) => ... // delegate Matching on Variant2
+ ...
+ _ => {
+ let __this_vi = match this { Variant1 => 0u, Variant2 => 1u, ... };
+ let __that_vi = match that { Variant1 => 0u, Variant2 => 1u, ... };
+ ... // catch-all remainder can inspect above variant index values.
+ }
+ }
+ ~~~
+ */
+ fn build_enum_match_tuple(
+ &self,
+ cx: &mut ExtCtxt,
+ trait_: &TraitDef,
+ enum_def: &EnumDef,
+ type_ident: Ident,
+ self_args: &[Gc<Expr>],
+ nonself_args: &[Gc<Expr>]) -> Gc<Expr> {
+
+ let sp = trait_.span;
+ let variants = &enum_def.variants;
+
+ let self_arg_names = self_args.iter().enumerate()
+ .map(|(arg_count, _self_arg)| {
+ if arg_count == 0 {
+ "__self".to_string()
+ } else {
+ format!("__arg_{}", arg_count)
+ }
+ })
+ .collect::<Vec<String>>();
+
+ let self_arg_idents = self_arg_names.iter()
+ .map(|name|cx.ident_of(name.as_slice()))
+ .collect::<Vec<ast::Ident>>();
+
+ // The `vi_idents` will be bound, solely in the catch-all, to
+ // a series of let statements mapping each self_arg to a uint
+ // corresponding to its variant index.
+ let vi_idents : Vec<ast::Ident> = self_arg_names.iter()
+ .map(|name| { let vi_suffix = format!("{:s}_vi", name.as_slice());
+ cx.ident_of(vi_suffix.as_slice()) })
+ .collect::<Vec<ast::Ident>>();
+
+ // Builds, via callback to call_substructure_method, the
+ // delegated expression that handles the catch-all case,
+ // using `__variants_tuple` to drive logic if necessary.
+ let catch_all_substructure = EnumNonMatchingCollapsed(
+ self_arg_idents, variants.as_slice(), vi_idents.as_slice());
+
+ // These arms are of the form:
+ // (Variant1, Variant1, ...) => Body1
+ // (Variant2, Variant2, ...) => Body2
+ // ...
+ // where each tuple has length = self_args.len()
+ let mut match_arms : Vec<ast::Arm> = variants.iter().enumerate()
+ .map(|(index, &variant)| {
+
+ // These self_pats have form Variant1, Variant2, ...
+ let self_pats : Vec<(Gc<ast::Pat>,
+ Vec<(Span, Option<Ident>, Gc<Expr>)>)>;
+ self_pats = self_arg_names.iter()
+ .map(|self_arg_name|
+ trait_.create_enum_variant_pattern(
+ cx, &*variant, self_arg_name.as_slice(),
+ ast::MutImmutable))
+ .collect();
+
+ // A single arm has form (&VariantK, &VariantK, ...) => BodyK
+ // (see "Final wrinkle" note below for why.)
+ let subpats = self_pats.iter()
+ .map(|&(p, ref _idents)| cx.pat(sp, ast::PatRegion(p)))
+ .collect::<Vec<Gc<ast::Pat>>>();
+
+ // Here is the pat = `(&VariantK, &VariantK, ...)`
+ let single_pat = cx.pat(sp, ast::PatTup(subpats));
+
+ // For the BodyK, we need to delegate to our caller,
+ // passing it an EnumMatching to indicate which case
+ // we are in.
+
+ // All of the Self args have the same variant in these
+ // cases. So we transpose the info in self_pats to
+ // gather the getter expressions together, in the form
+ // that EnumMatching expects.
+
+ // The transposition is driven by walking across the
+ // arg fields of the variant for the first self pat.
+ let &(_, ref self_arg_fields) = self_pats.get(0);
+
+ let field_tuples : Vec<FieldInfo>;
+
+ field_tuples = self_arg_fields.iter().enumerate()
+ // For each arg field of self, pull out its getter expr ...
+ .map(|(field_index, &(sp, opt_ident, self_getter_expr))| {
+ // ... but FieldInfo also wants getter expr
+ // for matching other arguments of Self type;
+ // so walk across the *other* self_pats and
+ // pull out getter for same field in each of
+ // them (using `field_index` tracked above).
+ // That is the heart of the transposition.
+ let others = self_pats.tail().iter()
+ .map(|&(_pat, ref fields)| {
+
+ let &(_, _opt_ident, other_getter_expr) =
+ fields.get(field_index);
+
+ // All Self args have same variant, so
+ // opt_idents are the same. (Assert
+ // here to make it self-evident that
+ // it is okay to ignore `_opt_ident`.)
+ assert!(opt_ident == _opt_ident);
+
+ other_getter_expr
+ }).collect::<Vec<Gc<Expr>>>();
+
+ FieldInfo { span: sp,
+ name: opt_ident,
+ self_: self_getter_expr,
+ other: others,
+ }
+ }).collect::<Vec<FieldInfo>>();
+
+ // Now, for some given VariantK, we have built up
+ // expressions for referencing every field of every
+ // Self arg, assuming all are instances of VariantK.
+ // Build up code associated with such a case.
+ let substructure = EnumMatching(index, variant, field_tuples);
+ let arm_expr = self.call_substructure_method(
+ cx, trait_, type_ident, self_args, nonself_args,
+ &substructure);
+
+ cx.arm(sp, vec![single_pat], arm_expr)
+ }).collect();
+
+ // We will usually need the catch-all after matching the
+ // tuples `(VariantK, VariantK, ...)` for each VariantK of the
+ // enum. But:
+ //
+ // * when there is only one Self arg, the arms above suffice
+ // (and the deriving we call back into may not be prepared to
+ // handle EnumNonMatchCollapsed), and,
+ //
+ // * when the enum has only one variant, the single arm that
+ // is already present always suffices.
+ //
+ // * In either of the two cases above, if we *did* add a
+ // catch-all `_` match, it would trigger the
+ // unreachable-pattern error.
+ //
+ if variants.len() > 1 && self_args.len() > 1 {
+ let arms : Vec<ast::Arm> = variants.iter().enumerate()
+ .map(|(index, &variant)| {
+ let pat = variant_to_pat(cx, sp, &*variant);
+ let lit = ast::LitUint(index as u64, ast::TyU);
+ cx.arm(sp, vec![pat], cx.expr_lit(sp, lit))
+ }).collect();
+
+ // Build a series of let statements mapping each self_arg
+ // to a uint corresponding to its variant index.
+ // i.e. for `enum E<T> { A, B(1), C(T, T) }`, and a deriving
+ // with three Self args, builds three statements:
+ //
+ // ```
+ // let __self0_vi = match self {
+ // A => 0u, B(..) => 1u, C(..) => 2u
+ // };
+ // let __self1_vi = match __arg1 {
+ // A => 0u, B(..) => 1u, C(..) => 2u
+ // };
+ // let __self2_vi = match __arg2 {
+ // A => 0u, B(..) => 1u, C(..) => 2u
+ // };
+ // ```
+ let mut index_let_stmts : Vec<Gc<ast::Stmt>> = Vec::new();
+ for (&ident, &self_arg) in vi_idents.iter().zip(self_args.iter()) {
+ let variant_idx = cx.expr_match(sp, self_arg, arms.clone());
+ let let_stmt = cx.stmt_let(sp, false, ident, variant_idx);
+ index_let_stmts.push(let_stmt);
+ }
+
+ let arm_expr = self.call_substructure_method(
+ cx, trait_, type_ident, self_args, nonself_args,
+ &catch_all_substructure);
+
+ // Builds the expression:
+ // {
+ // let __self0_vi = ...;
+ // let __self1_vi = ...;
+ // ...
+ // <delegated expression referring to __self0_vi, et al.>
+ // }
+ let arm_expr = cx.expr_block(
+ cx.block_all(sp, Vec::new(), index_let_stmts, Some(arm_expr)));
+
+ // Builds arm:
+ // _ => { let __self0_vi = ...;
+ // let __self1_vi = ...;
+ // ...
+ // <delegated expression as above> }
+ let catch_all_match_arm =
+ cx.arm(sp, vec![cx.pat_wild(sp)], arm_expr);
+
+ match_arms.push(catch_all_match_arm);
+
+ } else if variants.len() == 0 {
+ // As an additional wrinkle, For a zero-variant enum A,
+ // currently the compiler
+ // will accept `fn (a: &Self) { match *a { } }`
+ // but rejects `fn (a: &Self) { match (&*a,) { } }`
+ // as well as `fn (a: &Self) { match ( *a,) { } }`
+ //
+ // This means that the strategy of building up a tuple of
+ // all Self arguments fails when Self is a zero variant
+ // enum: rustc rejects the expanded program, even though
+ // the actual code tends to be impossible to execute (at
+ // least safely), according to the type system.
+ //
+ // The most expedient fix for this is to just let the
+ // code fall through to the catch-all. But even this is
+ // error-prone, since the catch-all as defined above would
+ // generate code like this:
+ //
+ // _ => { let __self0 = match *self { };
+ // let __self1 = match *__arg_0 { };
+ // <catch-all-expr> }
+ //
+ // Which is yields bindings for variables which type
+ // inference cannot resolve to unique types.
+ //
+ // One option to the above might be to add explicit type
+ // annotations. But the *only* reason to go down that path
+ // would be to try to make the expanded output consistent
+ // with the case when the number of enum variants >= 1.
+ //
+ // That just isn't worth it. In fact, trying to generate
+ // sensible code for *any* deriving on a zero-variant enum
+ // does not make sense. But at the same time, for now, we
+ // do not want to cause a compile failure just because the
+ // user happened to attach a deriving to their
+ // zero-variant enum.
+ //
+ // Instead, just generate a failing expression for the
+ // zero variant case, skipping matches and also skipping
+ // delegating back to the end user code entirely.
+ //
+ // (See also #4499 and #12609; note that some of the
+ // discussions there influence what choice we make here;
+ // e.g. if we feature-gate `match x { ... }` when x refers
+ // to an uninhabited type (e.g. a zero-variant enum or a
+ // type holding such an enum), but do not feature-gate
+ // zero-variant enums themselves, then attempting to
+ // derive Show on such a type could here generate code
+ // that needs the feature gate enabled.)
+
+ return cx.expr_unreachable(sp);
+ }
+
+ // Final wrinkle: the self_args are expressions that deref
+ // down to desired l-values, but we cannot actually deref
+ // them when they are fed as r-values into a tuple
+ // expression; here add a layer of borrowing, turning
+ // `(*self, *__arg_0, ...)` into `(&*self, &*__arg_0, ...)`.
+ let borrowed_self_args = self_args.iter()
+ .map(|&self_arg| cx.expr_addr_of(sp, self_arg))
+ .collect::<Vec<Gc<ast::Expr>>>();
+ let match_arg = cx.expr(sp, ast::ExprTup(borrowed_self_args));
+ cx.expr_match(sp, match_arg, match_arms)
+ }
+
fn expand_static_enum_method_body(&self,
cx: &mut ExtCtxt,
trait_: &TraitDef,
f: |&mut ExtCtxt, Span, Gc<Expr>, Gc<Expr>, &[Gc<Expr>]| -> Gc<Expr>,
base: Gc<Expr>,
enum_nonmatch_f: EnumNonMatchFunc,
+ enum_nonmatch_g: EnumNonMatchCollapsedFunc,
cx: &mut ExtCtxt,
trait_span: Span,
substructure: &Substructure)
})
}
},
- EnumNonMatching(ref all_enums) => enum_nonmatch_f(cx, trait_span,
- *all_enums,
- substructure.nonself_args),
+ EnumNonMatching(ref all_enums) =>
+ enum_nonmatch_f(cx, trait_span, *all_enums,
+ substructure.nonself_args),
+ EnumNonMatchingCollapsed(ref all_args, _, tuple) =>
+ enum_nonmatch_g(cx, trait_span, (all_args.as_slice(), tuple),
+ substructure.nonself_args),
StaticEnum(..) | StaticStruct(..) => {
cx.span_bug(trait_span, "static function in `deriving`")
}
#[inline]
pub fn cs_same_method(f: |&mut ExtCtxt, Span, Vec<Gc<Expr>>| -> Gc<Expr>,
enum_nonmatch_f: EnumNonMatchFunc,
+ enum_nonmatch_g: EnumNonMatchCollapsedFunc,
cx: &mut ExtCtxt,
trait_span: Span,
substructure: &Substructure)
f(cx, trait_span, called)
},
- EnumNonMatching(ref all_enums) => enum_nonmatch_f(cx, trait_span,
- *all_enums,
- substructure.nonself_args),
+ EnumNonMatching(ref all_enums) =>
+ enum_nonmatch_f(cx, trait_span, *all_enums,
+ substructure.nonself_args),
+ EnumNonMatchingCollapsed(ref all_self_args, _, tuple) =>
+ enum_nonmatch_g(cx, trait_span, (all_self_args.as_slice(), tuple),
+ substructure.nonself_args),
StaticEnum(..) | StaticStruct(..) => {
cx.span_bug(trait_span, "static function in `deriving`")
}
f: |&mut ExtCtxt, Span, Gc<Expr>, Gc<Expr>| -> Gc<Expr>,
base: Gc<Expr>,
enum_nonmatch_f: EnumNonMatchFunc,
+ enum_nonmatch_g: EnumNonMatchCollapsedFunc,
cx: &mut ExtCtxt,
trait_span: Span,
substructure: &Substructure)
}
},
enum_nonmatch_f,
+ enum_nonmatch_g,
cx, trait_span, substructure)
}
#[inline]
pub fn cs_binop(binop: ast::BinOp, base: Gc<Expr>,
enum_nonmatch_f: EnumNonMatchFunc,
+ enum_nonmatch_g: EnumNonMatchCollapsedFunc,
cx: &mut ExtCtxt, trait_span: Span,
substructure: &Substructure) -> Gc<Expr> {
cs_same_method_fold(
},
base,
enum_nonmatch_f,
+ enum_nonmatch_g,
cx, trait_span, substructure)
}
/// cs_binop with binop == or
#[inline]
pub fn cs_or(enum_nonmatch_f: EnumNonMatchFunc,
+ enum_nonmatch_g: EnumNonMatchCollapsedFunc,
cx: &mut ExtCtxt, span: Span,
substructure: &Substructure) -> Gc<Expr> {
cs_binop(ast::BiOr, cx.expr_bool(span, false),
enum_nonmatch_f,
+ enum_nonmatch_g,
cx, span, substructure)
}
/// cs_binop with binop == and
#[inline]
pub fn cs_and(enum_nonmatch_f: EnumNonMatchFunc,
+ enum_nonmatch_g: EnumNonMatchCollapsedFunc,
cx: &mut ExtCtxt, span: Span,
substructure: &Substructure) -> Gc<Expr> {
cs_binop(ast::BiAnd, cx.expr_bool(span, true),
enum_nonmatch_f,
+ enum_nonmatch_g,
cx, span, substructure)
}
projects / rust.git / commitdiff