rust/src/test/run-pass-fulldeps/pprust-expr-roundtrip.rs

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// ignore-cross-compile
// The general idea of this test is to enumerate all "interesting" expressions and check that
// `parse(print(e)) == e` for all `e`. Here's what's interesting, for the purposes of this test:
//
// 1. The test focuses on expression nesting, because interactions between different expression
// types are harder to test manually than single expression types in isolation.
//
// 2. The test only considers expressions of at most two nontrivial nodes. So it will check `x +
// x` and `x + (x - x)` but not `(x * x) + (x - x)`. The assumption here is that the correct
// handling of an expression might depend on the expression's parent, but doesn't depend on its
// siblings or any more distant ancestors.
//
// 3. The test only checks certain expression kinds. The assumption is that similar expression
// types, such as `if` and `while` or `+` and `-`, will be handled identically in the printer
// and parser. So if all combinations of exprs involving `if` work correctly, then combinations
// using `while`, `if let`, and so on will likely work as well.
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#![feature(rustc_private)]
extern crate rustc_data_structures;
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extern crate syntax;
use rustc_data_structures::thin_vec::ThinVec;
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use syntax::ast::*;
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use syntax::source_map::{Spanned, DUMMY_SP, FileName};
use syntax::source_map::FilePathMapping;
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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use syntax::mut_visit::{self, MutVisitor, visit_clobber};
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use syntax::parse::{self, ParseSess};
use syntax::print::pprust;
use syntax::ptr::P;
fn parse_expr(ps: &ParseSess, src: &str) -> P<Expr> {
let src_as_string = src.to_string();
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let mut p = parse::new_parser_from_source_str(ps,
FileName::Custom(src_as_string.clone()),
src_as_string);
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p.parse_expr().unwrap()
}
// Helper functions for building exprs
fn expr(kind: ExprKind) -> P<Expr> {
P(Expr {
id: DUMMY_NODE_ID,
node: kind,
span: DUMMY_SP,
attrs: ThinVec::new(),
})
}
fn make_x() -> P<Expr> {
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let seg = PathSegment::from_ident(Ident::from_str("x"));
let path = Path { segments: vec![seg], span: DUMMY_SP };
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expr(ExprKind::Path(None, path))
}
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/// Iterate over exprs of depth up to `depth`. The goal is to explore all "interesting"
/// combinations of expression nesting. For example, we explore combinations using `if`, but not
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/// `while` or `match`, since those should print and parse in much the same way as `if`.
fn iter_exprs(depth: usize, f: &mut FnMut(P<Expr>)) {
if depth == 0 {
f(make_x());
return;
}
let mut g = |e| f(expr(e));
for kind in 0 .. 16 {
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match kind {
0 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Box(e))),
1 => iter_exprs(depth - 1, &mut |e| g(ExprKind::Call(e, vec![]))),
2 => {
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let seg = PathSegment::from_ident(Ident::from_str("x"));
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iter_exprs(depth - 1, &mut |e| g(ExprKind::MethodCall(
seg.clone(), vec![e, make_x()])));
iter_exprs(depth - 1, &mut |e| g(ExprKind::MethodCall(
seg.clone(), vec![make_x(), e])));
},
3 => {
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let op = Spanned { span: DUMMY_SP, node: BinOpKind::Add };
iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, e, make_x())));
iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, make_x(), e)));
},
4 => {
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let op = Spanned { span: DUMMY_SP, node: BinOpKind::Mul };
iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, e, make_x())));
iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, make_x(), e)));
},
5 => {
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let op = Spanned { span: DUMMY_SP, node: BinOpKind::Shl };
iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, e, make_x())));
iter_exprs(depth - 1, &mut |e| g(ExprKind::Binary(op, make_x(), e)));
},
6 => {
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iter_exprs(depth - 1, &mut |e| g(ExprKind::Unary(UnOp::Deref, e)));
},
7 => {
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let block = P(Block {
stmts: Vec::new(),
id: DUMMY_NODE_ID,
rules: BlockCheckMode::Default,
span: DUMMY_SP,
});
iter_exprs(depth - 1, &mut |e| g(ExprKind::If(e, block.clone(), None)));
},
8 => {
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let decl = P(FnDecl {
inputs: vec![],
output: FunctionRetTy::Default(DUMMY_SP),
c_variadic: false,
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});
iter_exprs(depth - 1, &mut |e| g(
ExprKind::Closure(CaptureBy::Value,
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IsAsync::NotAsync,
Movability::Movable,
decl.clone(),
e,
DUMMY_SP)));
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},
9 => {
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iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(e, make_x())));
iter_exprs(depth - 1, &mut |e| g(ExprKind::Assign(make_x(), e)));
},
10 => {
iter_exprs(depth - 1, &mut |e| g(ExprKind::Field(e, Ident::from_str("f"))));
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},
11 => {
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iter_exprs(depth - 1, &mut |e| g(ExprKind::Range(
Some(e), Some(make_x()), RangeLimits::HalfOpen)));
iter_exprs(depth - 1, &mut |e| g(ExprKind::Range(
Some(make_x()), Some(e), RangeLimits::HalfOpen)));
},
12 => {
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iter_exprs(depth - 1, &mut |e| g(ExprKind::AddrOf(Mutability::Immutable, e)));
},
13 => {
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g(ExprKind::Ret(None));
iter_exprs(depth - 1, &mut |e| g(ExprKind::Ret(Some(e))));
},
14 => {
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let path = Path::from_ident(Ident::from_str("S"));
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g(ExprKind::Struct(path, vec![], Some(make_x())));
},
15 => {
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iter_exprs(depth - 1, &mut |e| g(ExprKind::Try(e)));
},
_ => panic!("bad counter value in iter_exprs"),
}
}
}
// Folders for manipulating the placement of `Paren` nodes. See below for why this is needed.
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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/// MutVisitor that removes all `ExprKind::Paren` nodes.
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struct RemoveParens;
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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impl MutVisitor for RemoveParens {
fn visit_expr(&mut self, e: &mut P<Expr>) {
match e.node.clone() {
ExprKind::Paren(inner) => *e = inner,
_ => {}
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};
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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mut_visit::noop_visit_expr(e, self);
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}
}
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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/// MutVisitor that inserts `ExprKind::Paren` nodes around every `Expr`.
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struct AddParens;
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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impl MutVisitor for AddParens {
fn visit_expr(&mut self, e: &mut P<Expr>) {
mut_visit::noop_visit_expr(e, self);
visit_clobber(e, |e| {
P(Expr {
id: DUMMY_NODE_ID,
node: ExprKind::Paren(e),
span: DUMMY_SP,
attrs: ThinVec::new(),
})
});
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}
}
fn main() {
syntax::with_default_globals(|| run());
}
fn run() {
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let ps = ParseSess::new(FilePathMapping::empty());
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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iter_exprs(2, &mut |mut e| {
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// If the pretty printer is correct, then `parse(print(e))` should be identical to `e`,
// modulo placement of `Paren` nodes.
let printed = pprust::expr_to_string(&e);
println!("printed: {}", printed);
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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let mut parsed = parse_expr(&ps, &printed);
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// We want to know if `parsed` is structurally identical to `e`, ignoring trivial
// differences like placement of `Paren`s or the exact ranges of node spans.
// Unfortunately, there is no easy way to make this comparison. Instead, we add `Paren`s
// everywhere we can, then pretty-print. This should give an unambiguous representation of
// each `Expr`, and it bypasses nearly all of the parenthesization logic, so we aren't
// relying on the correctness of the very thing we're testing.
Overhaul `syntax::fold::Folder`. This commit changes `syntax::fold::Folder` from a functional style (where most methods take a `T` and produce a new `T`) to a more imperative style (where most methods take and modify a `&mut T`), and renames it `syntax::mut_visit::MutVisitor`. The first benefit is speed. The functional style does not require any reallocations, due to the use of `P::map` and `MoveMap::move_{,flat_}map`. However, every field in the AST must be overwritten; even those fields that are unchanged are overwritten with the same value. This causes a lot of unnecessary memory writes. The imperative style reduces instruction counts by 1--3% across a wide range of workloads, particularly incremental workloads. The second benefit is conciseness; the imperative style is usually more concise. E.g. compare the old functional style: ``` fn fold_abc(&mut self, abc: ABC) { ABC { a: fold_a(abc.a), b: fold_b(abc.b), c: abc.c, } } ``` with the imperative style: ``` fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) { visit_a(a); visit_b(b); } ``` (The reductions get larger in more complex examples.) Overall, the patch removes over 200 lines of code -- even though the new code has more comments -- and a lot of the remaining lines have fewer characters. Some notes: - The old style used methods called `fold_*`. The new style mostly uses methods called `visit_*`, but there are a few methods that map a `T` to something other than a `T`, which are called `flat_map_*` (`T` maps to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s). - `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed `map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to reflect their slightly changed signatures. - Although this commit renames the `fold` module as `mut_visit`, it keeps it in the `fold.rs` file, so as not to confuse git. The next commit will rename the file.
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RemoveParens.visit_expr(&mut e);
AddParens.visit_expr(&mut e);
let text1 = pprust::expr_to_string(&e);
RemoveParens.visit_expr(&mut parsed);
AddParens.visit_expr(&mut parsed);
let text2 = pprust::expr_to_string(&parsed);
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assert!(text1 == text2,
"exprs are not equal:\n e = {:?}\n parsed = {:?}",
text1, text2);
});
}