src/libsyntax/ast_map/blocks.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! This module provides a simplified abstraction for working with
  12 //! code blocks identified by their integer node-id.  In particular,
  13 //! it captures a common set of attributes that all "function-like
  14 //! things" (represented by `FnLike` instances) share.  For example,
  15 //! all `FnLike` instances have a type signature (be it explicit or
  16 //! inferred).  And all `FnLike` instances have a body, i.e. the code
  17 //! that is run when the function-like thing it represents is invoked.
  18 //!
  19 //! With the above abstraction in place, one can treat the program
  20 //! text as a collection of blocks of code (and most such blocks are
  21 //! nested within a uniquely determined `FnLike`), and users can ask
  22 //! for the `Code` associated with a particular NodeId.
  23
  24 pub use self::Code::*;
  25
  26 use abi;
  27 use ast::{Block, FnDecl, NodeId};
  28 use ast;
  29 use ast_map::Node;
  30 use ast_map;
  31 use codemap::Span;
  32 use visit;
  33
  34 /// An FnLikeNode is a Node that is like a fn, in that it has a decl
  35 /// and a body (as well as a NodeId, a span, etc).
  36 ///
  37 /// More specifically, it is one of either:
  38 ///   - A function item,
  39 ///   - A closure expr (i.e. an ExprClosure), or
  40 ///   - The default implementation for a trait method.
  41 ///
  42 /// To construct one, use the `Code::from_node` function.
  43 #[derive(Copy, Clone)]
  44 pub struct FnLikeNode<'a> { node: ast_map::Node<'a> }
  45
  46 /// MaybeFnLike wraps a method that indicates if an object
  47 /// corresponds to some FnLikeNode.
  48 pub trait MaybeFnLike { fn is_fn_like(&self) -> bool; }
  49
  50 /// Components shared by fn-like things (fn items, methods, closures).
  51 pub struct FnParts<'a> {
  52     pub decl: &'a FnDecl,
  53     pub body: &'a Block,
  54     pub kind: visit::FnKind<'a>,
  55     pub span: Span,
  56     pub id:   NodeId,
  57 }
  58
  59 impl MaybeFnLike for ast::Item {
  60     fn is_fn_like(&self) -> bool {
  61         match self.node { ast::ItemFn(..) => true, _ => false, }
  62     }
  63 }
  64
  65 impl MaybeFnLike for ast::TraitItem {
  66     fn is_fn_like(&self) -> bool {
  67         match self.node { ast::MethodTraitItem(_, Some(_)) => true, _ => false, }
  68     }
  69 }
  70
  71 impl MaybeFnLike for ast::Expr {
  72     fn is_fn_like(&self) -> bool {
  73         match self.node {
  74             ast::ExprClosure(..) => true,
  75             _ => false,
  76         }
  77     }
  78 }
  79
  80 /// Carries either an FnLikeNode or a Block, as these are the two
  81 /// constructs that correspond to "code" (as in, something from which
  82 /// we can construct a control-flow graph).
  83 #[derive(Copy, Clone)]
  84 pub enum Code<'a> {
  85     FnLikeCode(FnLikeNode<'a>),
  86     BlockCode(&'a Block),
  87 }
  88
  89 impl<'a> Code<'a> {
  90     pub fn id(&self) -> ast::NodeId {
  91         match *self {
  92             FnLikeCode(node) => node.id(),
  93             BlockCode(block) => block.id,
  94         }
  95     }
  96
  97     /// Attempts to construct a Code from presumed FnLike or Block node input.
  98     pub fn from_node(node: Node) -> Option<Code> {
  99         fn new(node: Node) -> FnLikeNode { FnLikeNode { node: node } }
 100         match node {
 101             ast_map::NodeItem(item) if item.is_fn_like() =>
 102                 Some(FnLikeCode(new(node))),
 103             ast_map::NodeTraitItem(tm) if tm.is_fn_like() =>
 104                 Some(FnLikeCode(new(node))),
 105             ast_map::NodeImplItem(_) =>
 106                 Some(FnLikeCode(new(node))),
 107             ast_map::NodeExpr(e) if e.is_fn_like() =>
 108                 Some(FnLikeCode(new(node))),
 109             ast_map::NodeBlock(block) =>
 110                 Some(BlockCode(block)),
 111             _ =>
 112                 None,
 113         }
 114     }
 115 }
 116
 117 /// These are all the components one can extract from a fn item for
 118 /// use when implementing FnLikeNode operations.
 119 struct ItemFnParts<'a> {
 120     ident:    ast::Ident,
 121     decl:     &'a ast::FnDecl,
 122     unsafety: ast::Unsafety,
 123     abi:      abi::Abi,
 124     vis:      ast::Visibility,
 125     generics: &'a ast::Generics,
 126     body:     &'a Block,
 127     id:       ast::NodeId,
 128     span:     Span
 129 }
 130
 131 /// These are all the components one can extract from a closure expr
 132 /// for use when implementing FnLikeNode operations.
 133 struct ClosureParts<'a> {
 134     decl: &'a FnDecl,
 135     body: &'a Block,
 136     id: NodeId,
 137     span: Span
 138 }
 139
 140 impl<'a> ClosureParts<'a> {
 141     fn new(d: &'a FnDecl, b: &'a Block, id: NodeId, s: Span) -> ClosureParts<'a> {
 142         ClosureParts { decl: d, body: b, id: id, span: s }
 143     }
 144 }
 145
 146 impl<'a> FnLikeNode<'a> {
 147     pub fn to_fn_parts(self) -> FnParts<'a> {
 148         FnParts {
 149             decl: self.decl(),
 150             body: self.body(),
 151             kind: self.kind(),
 152             span: self.span(),
 153             id:   self.id(),
 154         }
 155     }
 156
 157     pub fn body(self) -> &'a Block {
 158         self.handle(|i: ItemFnParts<'a>|  &*i.body,
 159                     |_, _, _: &'a ast::MethodSig, _, body: &'a ast::Block, _|  body,
 160                     |c: ClosureParts<'a>| c.body)
 161     }
 162
 163     pub fn decl(self) -> &'a FnDecl {
 164         self.handle(|i: ItemFnParts<'a>|  &*i.decl,
 165                     |_, _, sig: &'a ast::MethodSig, _, _, _|  &sig.decl,
 166                     |c: ClosureParts<'a>| c.decl)
 167     }
 168
 169     pub fn span(self) -> Span {
 170         self.handle(|i: ItemFnParts|     i.span,
 171                     |_, _, _: &'a ast::MethodSig, _, _, span| span,
 172                     |c: ClosureParts|    c.span)
 173     }
 174
 175     pub fn id(self) -> NodeId {
 176         self.handle(|i: ItemFnParts|     i.id,
 177                     |id, _, _: &'a ast::MethodSig, _, _, _| id,
 178                     |c: ClosureParts|    c.id)
 179     }
 180
 181     pub fn kind(self) -> visit::FnKind<'a> {
 182         let item = |p: ItemFnParts<'a>| -> visit::FnKind<'a> {
 183             visit::FkItemFn(p.ident, p.generics, p.unsafety, p.abi, p.vis)
 184         };
 185         let closure = |_: ClosureParts| {
 186             visit::FkFnBlock
 187         };
 188         let method = |_, ident, sig: &'a ast::MethodSig, vis, _, _| {
 189             visit::FkMethod(ident, sig, vis)
 190         };
 191         self.handle(item, method, closure)
 192     }
 193
 194     fn handle<A, I, M, C>(self, item_fn: I, method: M, closure: C) -> A where
 195         I: FnOnce(ItemFnParts<'a>) -> A,
 196         M: FnOnce(NodeId,
 197                   ast::Ident,
 198                   &'a ast::MethodSig,
 199                   Option<ast::Visibility>,
 200                   &'a ast::Block,
 201                   Span)
 202                   -> A,
 203         C: FnOnce(ClosureParts<'a>) -> A,
 204     {
 205         match self.node {
 206             ast_map::NodeItem(i) => match i.node {
 207                 ast::ItemFn(ref decl, unsafety, abi, ref generics, ref block) =>
 208                     item_fn(ItemFnParts{
 209                         ident: i.ident, decl: &**decl, unsafety: unsafety, body: &**block,
 210                         generics: generics, abi: abi, vis: i.vis, id: i.id, span: i.span
 211                     }),
 212                 _ => panic!("item FnLikeNode that is not fn-like"),
 213             },
 214             ast_map::NodeTraitItem(ti) => match ti.node {
 215                 ast::MethodTraitItem(ref sig, Some(ref body)) => {
 216                     method(ti.id, ti.ident, sig, None, body, ti.span)
 217                 }
 218                 _ => panic!("trait method FnLikeNode that is not fn-like"),
 219             },
 220             ast_map::NodeImplItem(ii) => {
 221                 match ii.node {
 222                     ast::MethodImplItem(ref sig, ref body) => {
 223                         method(ii.id, ii.ident, sig, Some(ii.vis), body, ii.span)
 224                     }
 225                     ast::TypeImplItem(_) |
 226                     ast::MacImplItem(_) => {
 227                         panic!("impl method FnLikeNode that is not fn-like")
 228                     }
 229                 }
 230             }
 231             ast_map::NodeExpr(e) => match e.node {
 232                 ast::ExprClosure(_, ref decl, ref block) =>
 233                     closure(ClosureParts::new(&**decl, &**block, e.id, e.span)),
 234                 _ => panic!("expr FnLikeNode that is not fn-like"),
 235             },
 236             _ => panic!("other FnLikeNode that is not fn-like"),
 237         }
 238     }
 239 }