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hygiene: Rewrite apply_mark_internal to be more understandable #139083

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Mar 31, 2025
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hygiene: Rewrite apply_mark_internal to be more understandable #139083

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121 changes: 61 additions & 60 deletions compiler/rustc_span/src/hygiene.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,21 @@ pub struct SyntaxContextData {
}

impl SyntaxContextData {
fn new(
(parent, outer_expn, outer_transparency): SyntaxContextKey,
opaque: SyntaxContext,
opaque_and_semitransparent: SyntaxContext,
) -> SyntaxContextData {
SyntaxContextData {
outer_expn,
outer_transparency,
parent,
opaque,
opaque_and_semitransparent,
dollar_crate_name: kw::DollarCrate,
}
}

fn root() -> SyntaxContextData {
SyntaxContextData {
outer_expn: ExpnId::root(),
Expand Down Expand Up @@ -543,7 +558,7 @@ impl HygieneData {
) -> SyntaxContext {
assert_ne!(expn_id, ExpnId::root());
if transparency == Transparency::Opaque {
return self.apply_mark_internal(ctxt, expn_id, transparency);
return self.alloc_ctxt(ctxt, expn_id, transparency);
}

let call_site_ctxt = self.expn_data(expn_id).call_site.ctxt();
Expand All @@ -554,7 +569,7 @@ impl HygieneData {
};

if call_site_ctxt.is_root() {
return self.apply_mark_internal(ctxt, expn_id, transparency);
return self.alloc_ctxt(ctxt, expn_id, transparency);
}

// Otherwise, `expn_id` is a macros 1.0 definition and the call site is in a
Expand All @@ -567,74 +582,60 @@ impl HygieneData {
//
// See the example at `test/ui/hygiene/legacy_interaction.rs`.
for (expn_id, transparency) in self.marks(ctxt) {
call_site_ctxt = self.apply_mark_internal(call_site_ctxt, expn_id, transparency);
call_site_ctxt = self.alloc_ctxt(call_site_ctxt, expn_id, transparency);
}
self.apply_mark_internal(call_site_ctxt, expn_id, transparency)
self.alloc_ctxt(call_site_ctxt, expn_id, transparency)
}

fn apply_mark_internal(
/// Allocate a new context with the given key, or retrieve it from cache if the given key
/// already exists. The auxiliary fields are calculated from the key.
fn alloc_ctxt(
&mut self,
ctxt: SyntaxContext,
parent: SyntaxContext,
expn_id: ExpnId,
transparency: Transparency,
) -> SyntaxContext {
let syntax_context_data = &mut self.syntax_context_data;
debug_assert!(!syntax_context_data[ctxt.0 as usize].is_decode_placeholder());
let mut opaque = syntax_context_data[ctxt.0 as usize].opaque;
let mut opaque_and_semitransparent =
syntax_context_data[ctxt.0 as usize].opaque_and_semitransparent;

if transparency >= Transparency::Opaque {
let parent = opaque;
opaque = *self
.syntax_context_map
.entry((parent, expn_id, transparency))
.or_insert_with(|| {
let new_opaque = SyntaxContext::from_usize(syntax_context_data.len());
syntax_context_data.push(SyntaxContextData {
outer_expn: expn_id,
outer_transparency: transparency,
parent,
opaque: new_opaque,
opaque_and_semitransparent: new_opaque,
dollar_crate_name: kw::DollarCrate,
});
new_opaque
});
}
debug_assert!(!self.syntax_context_data[parent.0 as usize].is_decode_placeholder());

if transparency >= Transparency::SemiTransparent {
let parent = opaque_and_semitransparent;
opaque_and_semitransparent = *self
.syntax_context_map
.entry((parent, expn_id, transparency))
.or_insert_with(|| {
let new_opaque_and_semitransparent =
SyntaxContext::from_usize(syntax_context_data.len());
syntax_context_data.push(SyntaxContextData {
outer_expn: expn_id,
outer_transparency: transparency,
parent,
opaque,
opaque_and_semitransparent: new_opaque_and_semitransparent,
dollar_crate_name: kw::DollarCrate,
});
new_opaque_and_semitransparent
});
// Look into the cache first.
let key = (parent, expn_id, transparency);
if let Some(ctxt) = self.syntax_context_map.get(&key) {
return *ctxt;
}

let parent = ctxt;
*self.syntax_context_map.entry((parent, expn_id, transparency)).or_insert_with(|| {
syntax_context_data.push(SyntaxContextData {
outer_expn: expn_id,
outer_transparency: transparency,
parent,
opaque,
opaque_and_semitransparent,
dollar_crate_name: kw::DollarCrate,
});
SyntaxContext::from_usize(syntax_context_data.len() - 1)
})
// Reserve a new syntax context.
let ctxt = SyntaxContext::from_usize(self.syntax_context_data.len());
self.syntax_context_data.push(SyntaxContextData::decode_placeholder());
self.syntax_context_map.insert(key, ctxt);

// Opaque and semi-transparent versions of the parent. Note that they may be equal to the
// parent itself. E.g. `parent_opaque` == `parent` if the expn chain contains only opaques,
// and `parent_opaque_and_semitransparent` == `parent` if the expn contains only opaques
// and semi-transparents.
let parent_opaque = self.syntax_context_data[parent.0 as usize].opaque;
let parent_opaque_and_semitransparent =
self.syntax_context_data[parent.0 as usize].opaque_and_semitransparent;

// Evaluate opaque and semi-transparent versions of the new syntax context.
let (opaque, opaque_and_semitransparent) = match transparency {
Transparency::Transparent => (parent_opaque, parent_opaque_and_semitransparent),
Transparency::SemiTransparent => (
parent_opaque,
// Will be the same as `ctxt` if the expn chain contains only opaques and semi-transparents.
self.alloc_ctxt(parent_opaque_and_semitransparent, expn_id, transparency),
),
Transparency::Opaque => (
// Will be the same as `ctxt` if the expn chain contains only opaques.
self.alloc_ctxt(parent_opaque, expn_id, transparency),
// Will be the same as `ctxt` if the expn chain contains only opaques and semi-transparents.
self.alloc_ctxt(parent_opaque_and_semitransparent, expn_id, transparency),
),
};

// Fill the full data, now that we have it.
self.syntax_context_data[ctxt.as_u32() as usize] =
SyntaxContextData::new(key, opaque, opaque_and_semitransparent);
ctxt
}
}

Expand Down
20 changes: 10 additions & 10 deletions tests/ui/proc-macro/nonterminal-token-hygiene.stdout
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Original file line number Diff line number Diff line change
Expand Up @@ -5,19 +5,19 @@ PRINT-BANG INPUT (DEBUG): TokenStream [
stream: TokenStream [
Ident {
ident: "struct",
span: $DIR/nonterminal-token-hygiene.rs:32:5: 32:11 (#4),
span: $DIR/nonterminal-token-hygiene.rs:32:5: 32:11 (#5),
},
Ident {
ident: "S",
span: $DIR/nonterminal-token-hygiene.rs:32:12: 32:13 (#4),
span: $DIR/nonterminal-token-hygiene.rs:32:12: 32:13 (#5),
},
Punct {
ch: ';',
spacing: Alone,
span: $DIR/nonterminal-token-hygiene.rs:32:13: 32:14 (#4),
span: $DIR/nonterminal-token-hygiene.rs:32:13: 32:14 (#5),
},
],
span: $DIR/nonterminal-token-hygiene.rs:22:27: 22:32 (#5),
span: $DIR/nonterminal-token-hygiene.rs:22:27: 22:32 (#4),
},
]
#![feature /* 0#0 */(prelude_import)]
Expand Down Expand Up @@ -59,7 +59,7 @@ macro_rules! outer
struct S /* 0#0 */;
macro inner /* 0#3 */ { () => { print_bang! { struct S; } } }

struct S /* 0#4 */;
struct S /* 0#5 */;
// OK, not a duplicate definition of `S`

fn main /* 0#0 */() {}
Expand All @@ -70,7 +70,7 @@ crate0::{{expn0}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt:
crate0::{{expn1}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt: #0, kind: AstPass(StdImports)
crate0::{{expn2}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt: #0, kind: Macro(Bang, "outer")
crate0::{{expn3}}: parent: crate0::{{expn2}}, call_site_ctxt: #3, def_site_ctxt: #3, kind: Macro(Bang, "inner")
crate0::{{expn4}}: parent: crate0::{{expn3}}, call_site_ctxt: #5, def_site_ctxt: #0, kind: Macro(Bang, "print_bang")
crate0::{{expn4}}: parent: crate0::{{expn3}}, call_site_ctxt: #4, def_site_ctxt: #0, kind: Macro(Bang, "print_bang")
crate1::{{expnNNN}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt: #0, kind: Macro(Attr, "diagnostic::on_unimplemented")
crate1::{{expnNNN}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt: #0, kind: Macro(Attr, "diagnostic::on_unimplemented")
crate1::{{expnNNN}}: parent: crate0::{{expn0}}, call_site_ctxt: #0, def_site_ctxt: #0, kind: Macro(Attr, "diagnostic::on_unimplemented")
Expand All @@ -83,9 +83,9 @@ SyntaxContexts:
#1: parent: #0, outer_mark: (crate0::{{expn1}}, Opaque)
#2: parent: #0, outer_mark: (crate0::{{expn1}}, Transparent)
#3: parent: #0, outer_mark: (crate0::{{expn2}}, SemiTransparent)
#4: parent: #0, outer_mark: (crate0::{{expn3}}, Opaque)
#5: parent: #3, outer_mark: (crate0::{{expn3}}, Opaque)
#4: parent: #3, outer_mark: (crate0::{{expn3}}, Opaque)
#5: parent: #0, outer_mark: (crate0::{{expn3}}, Opaque)
#6: parent: #0, outer_mark: (crate0::{{expn4}}, Opaque)
#7: parent: #5, outer_mark: (crate0::{{expn4}}, Transparent)
#8: parent: #4, outer_mark: (crate0::{{expn4}}, SemiTransparent)
#7: parent: #4, outer_mark: (crate0::{{expn4}}, Transparent)
#8: parent: #5, outer_mark: (crate0::{{expn4}}, SemiTransparent)
*/
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