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Auto merge of #34374 - jseyfried:fix_hygiene_bug, r=nrc
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Fix macro hygiene regression

The regression was caused by #32923, which is currently in beta.

The following is an example of regressed code:
```rust
fn main() {
    let x = 0;
    macro_rules! foo { () => {
        println!("{}", x); // prints `0` on stable and after this PR, prints `1` on beta and nightly
    } }

    let x = 1;
    foo!();
}
```

For code to regress, the following is necessary (but not sufficient):
 - There must be a local variable before a macro in a block, and the macro must use the variable.
 - There must be a second local variable with the same name after the macro.
 - The macro must be invoked in a statement position after the second local variable.

For example, if the `let x = 0;` from the breaking example were commented out, it would (correctly) not compile on beta/nightly. If the semicolon were removed from `foo!();`, it would (correctly) print `0` on beta and nightly.

r? @nrc
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@bors
bors committed Jun 23, 2016
2 parents 6dcc2c1 + eef8485 commit 4960f2f
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Showing 3 changed files with 163 additions and 596 deletions.
264 changes: 3 additions & 261 deletions src/libsyntax/ext/expand.rs
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Expand Up @@ -681,7 +681,7 @@ pub struct IdentRenamer<'a> {

impl<'a> Folder for IdentRenamer<'a> {
fn fold_ident(&mut self, id: Ident) -> Ident {
Ident::new(id.name, mtwt::apply_renames(self.renames, id.ctxt))
mtwt::apply_renames(self.renames, id)
}
fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
fold::noop_fold_mac(mac, self)
Expand All @@ -705,8 +705,7 @@ impl<'a> Folder for PatIdentRenamer<'a> {

pat.map(|ast::Pat {id, node, span}| match node {
PatKind::Ident(binding_mode, Spanned{span: sp, node: ident}, sub) => {
let new_ident = Ident::new(ident.name,
mtwt::apply_renames(self.renames, ident.ctxt));
let new_ident = mtwt::apply_renames(self.renames, ident);
let new_node =
PatKind::Ident(binding_mode,
Spanned{span: sp, node: new_ident},
Expand Down Expand Up @@ -1266,7 +1265,7 @@ mod tests {
use ext::mtwt;
use fold::Folder;
use parse;
use parse::token::{self, keywords};
use parse::token;
use util::parser_testing::{string_to_parser};
use util::parser_testing::{string_to_pat, string_to_crate, strs_to_idents};
use visit;
Expand Down Expand Up @@ -1396,267 +1395,10 @@ mod tests {
);
}

// renaming tests expand a crate and then check that the bindings match
// the right varrefs. The specification of the test case includes the
// text of the crate, and also an array of arrays. Each element in the
// outer array corresponds to a binding in the traversal of the AST
// induced by visit. Each of these arrays contains a list of indexes,
// interpreted as the varrefs in the varref traversal that this binding
// should match. So, for instance, in a program with two bindings and
// three varrefs, the array [[1, 2], [0]] would indicate that the first
// binding should match the second two varrefs, and the second binding
// should match the first varref.
//
// Put differently; this is a sparse representation of a boolean matrix
// indicating which bindings capture which identifiers.
//
// Note also that this matrix is dependent on the implicit ordering of
// the bindings and the varrefs discovered by the name-finder and the path-finder.
//
// The comparisons are done post-mtwt-resolve, so we're comparing renamed
// names; differences in marks don't matter any more.
//
// oog... I also want tests that check "bound-identifier-=?". That is,
// not just "do these have the same name", but "do they have the same
// name *and* the same marks"? Understanding this is really pretty painful.
// in principle, you might want to control this boolean on a per-varref basis,
// but that would make things even harder to understand, and might not be
// necessary for thorough testing.
type RenamingTest = (&'static str, Vec<Vec<usize>>, bool);

#[test]
fn automatic_renaming () {
let tests: Vec<RenamingTest> =
vec!(// b & c should get new names throughout, in the expr too:
("fn a() -> i32 { let b = 13; let c = b; b+c }",
vec!(vec!(0,1),vec!(2)), false),
// both x's should be renamed (how is this causing a bug?)
("fn main () {let x: i32 = 13;x;}",
vec!(vec!(0)), false),
// the use of b after the + should be renamed, the other one not:
("macro_rules! f (($x:ident) => (b + $x)); fn a() -> i32 { let b = 13; f!(b)}",
vec!(vec!(1)), false),
// the b before the plus should not be renamed (requires marks)
("macro_rules! f (($x:ident) => ({let b=9; ($x + b)})); fn a() -> i32 { f!(b)}",
vec!(vec!(1)), false),
// the marks going in and out of letty should cancel, allowing that $x to
// capture the one following the semicolon.
// this was an awesome test case, and caught a *lot* of bugs.
("macro_rules! letty(($x:ident) => (let $x = 15;));
macro_rules! user(($x:ident) => ({letty!($x); $x}));
fn main() -> i32 {user!(z)}",
vec!(vec!(0)), false)
);
for (idx,s) in tests.iter().enumerate() {
run_renaming_test(s,idx);
}
}

// no longer a fixme #8062: this test exposes a *potential* bug; our system does
// not behave exactly like MTWT, but a conversation with Matthew Flatt
// suggests that this can only occur in the presence of local-expand, which
// we have no plans to support. ... unless it's needed for item hygiene....
#[ignore]
#[test]
fn issue_8062(){
run_renaming_test(
&("fn main() {let hrcoo = 19; macro_rules! getx(()=>(hrcoo)); getx!();}",
vec!(vec!(0)), true), 0)
}

// FIXME #6994:
// the z flows into and out of two macros (g & f) along one path, and one
// (just g) along the other, so the result of the whole thing should
// be "let z_123 = 3; z_123"
#[ignore]
#[test]
fn issue_6994(){
run_renaming_test(
&("macro_rules! g (($x:ident) =>
({macro_rules! f(($y:ident)=>({let $y=3;$x}));f!($x)}));
fn a(){g!(z)}",
vec!(vec!(0)),false),
0)
}

// match variable hygiene. Should expand into
// fn z() {match 8 {x_1 => {match 9 {x_2 | x_2 if x_2 == x_1 => x_2 + x_1}}}}
#[test]
fn issue_9384(){
run_renaming_test(
&("macro_rules! bad_macro (($ex:expr) => ({match 9 {x | x if x == $ex => x + $ex}}));
fn z() {match 8 {x => bad_macro!(x)}}",
// NB: the third "binding" is the repeat of the second one.
vec!(vec!(1,3),vec!(0,2),vec!(0,2)),
true),
0)
}

// interpolated nodes weren't getting labeled.
// should expand into
// fn main(){let g1_1 = 13; g1_1}}
#[test]
fn pat_expand_issue_15221(){
run_renaming_test(
&("macro_rules! inner ( ($e:pat ) => ($e));
macro_rules! outer ( ($e:pat ) => (inner!($e)));
fn main() { let outer!(g) = 13; g;}",
vec!(vec!(0)),
true),
0)
}

// create a really evil test case where a $x appears inside a binding of $x
// but *shouldn't* bind because it was inserted by a different macro....
// can't write this test case until we have macro-generating macros.

// method arg hygiene
// method expands to fn get_x(&self_0, x_1: i32) {self_0 + self_2 + x_3 + x_1}
#[test]
fn method_arg_hygiene(){
run_renaming_test(
&("macro_rules! inject_x (()=>(x));
macro_rules! inject_self (()=>(self));
struct A;
impl A{fn get_x(&self, x: i32) {self + inject_self!() + inject_x!() + x;} }",
vec!(vec!(0),vec!(3)),
true),
0)
}

// ooh, got another bite?
// expands to struct A; impl A {fn thingy(&self_1) {self_1;}}
#[test]
fn method_arg_hygiene_2(){
run_renaming_test(
&("struct A;
macro_rules! add_method (($T:ty) =>
(impl $T { fn thingy(&self) {self;} }));
add_method!(A);",
vec!(vec!(0)),
true),
0)
}

// item fn hygiene
// expands to fn q(x_1: i32){fn g(x_2: i32){x_2 + x_1};}
#[test]
fn issue_9383(){
run_renaming_test(
&("macro_rules! bad_macro (($ex:expr) => (fn g(x: i32){ x + $ex }));
fn q(x: i32) { bad_macro!(x); }",
vec!(vec!(1),vec!(0)),true),
0)
}

// closure arg hygiene (ExprKind::Closure)
// expands to fn f(){(|x_1 : i32| {(x_2 + x_1)})(3);}
#[test]
fn closure_arg_hygiene(){
run_renaming_test(
&("macro_rules! inject_x (()=>(x));
fn f(){(|x : i32| {(inject_x!() + x)})(3);}",
vec!(vec!(1)),
true),
0)
}

// macro_rules in method position. Sadly, unimplemented.
#[test]
fn macro_in_method_posn(){
expand_crate_str(
"macro_rules! my_method (() => (fn thirteen(&self) -> i32 {13}));
struct A;
impl A{ my_method!(); }
fn f(){A.thirteen;}".to_string());
}

// another nested macro
// expands to impl Entries {fn size_hint(&self_1) {self_1;}
#[test]
fn item_macro_workaround(){
run_renaming_test(
&("macro_rules! item { ($i:item) => {$i}}
struct Entries;
macro_rules! iterator_impl {
() => { item!( impl Entries { fn size_hint(&self) { self;}});}}
iterator_impl! { }",
vec!(vec!(0)), true),
0)
}

// run one of the renaming tests
fn run_renaming_test(t: &RenamingTest, test_idx: usize) {
let invalid_name = keywords::Invalid.name();
let (teststr, bound_connections, bound_ident_check) = match *t {
(ref str,ref conns, bic) => (str.to_string(), conns.clone(), bic)
};
let cr = expand_crate_str(teststr.to_string());
let bindings = crate_bindings(&cr);
let varrefs = crate_varrefs(&cr);

// must be one check clause for each binding:
assert_eq!(bindings.len(),bound_connections.len());
for (binding_idx,shouldmatch) in bound_connections.iter().enumerate() {
let binding_name = mtwt::resolve(bindings[binding_idx]);
let binding_marks = mtwt::marksof(bindings[binding_idx].ctxt, invalid_name);
// shouldmatch can't name varrefs that don't exist:
assert!((shouldmatch.is_empty()) ||
(varrefs.len() > *shouldmatch.iter().max().unwrap()));
for (idx,varref) in varrefs.iter().enumerate() {
let print_hygiene_debug_info = || {
// good lord, you can't make a path with 0 segments, can you?
let final_varref_ident = match varref.segments.last() {
Some(pathsegment) => pathsegment.identifier,
None => panic!("varref with 0 path segments?")
};
let varref_name = mtwt::resolve(final_varref_ident);
let varref_idents : Vec<ast::Ident>
= varref.segments.iter().map(|s| s.identifier)
.collect();
println!("varref #{}: {:?}, resolves to {}",idx, varref_idents, varref_name);
println!("varref's first segment's string: \"{}\"", final_varref_ident);
println!("binding #{}: {}, resolves to {}",
binding_idx, bindings[binding_idx], binding_name);
mtwt::with_sctable(|x| mtwt::display_sctable(x));
};
if shouldmatch.contains(&idx) {
// it should be a path of length 1, and it should
// be free-identifier=? or bound-identifier=? to the given binding
assert_eq!(varref.segments.len(),1);
let varref_name = mtwt::resolve(varref.segments[0].identifier);
let varref_marks = mtwt::marksof(varref.segments[0]
.identifier
.ctxt,
invalid_name);
if !(varref_name==binding_name) {
println!("uh oh, should match but doesn't:");
print_hygiene_debug_info();
}
assert_eq!(varref_name,binding_name);
if bound_ident_check {
// we're checking bound-identifier=?, and the marks
// should be the same, too:
assert_eq!(varref_marks,binding_marks.clone());
}
} else {
let varref_name = mtwt::resolve(varref.segments[0].identifier);
let fail = (varref.segments.len() == 1)
&& (varref_name == binding_name);
// temp debugging:
if fail {
println!("failure on test {}",test_idx);
println!("text of test case: \"{}\"", teststr);
println!("");
println!("uh oh, matches but shouldn't:");
print_hygiene_debug_info();
}
assert!(!fail);
}
}
}
}

#[test]
fn fmt_in_macro_used_inside_module_macro() {
let crate_str = "macro_rules! fmt_wrap(($b:expr)=>($b.to_string()));
Expand Down

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