From 552a8875bd5520c2e8c01ab05a12c304c730c5b9 Mon Sep 17 00:00:00 2001 From: Vadim Petrochenkov Date: Mon, 9 Mar 2020 20:50:12 +0300 Subject: [PATCH] expand: Implement support for retrying macro expansions --- src/librustc_builtin_macros/deriving/mod.rs | 6 +- src/librustc_expand/base.rs | 19 ++- src/librustc_expand/expand.rs | 145 ++++++++++++++------ src/librustc_expand/proc_macro.rs | 8 +- 4 files changed, 124 insertions(+), 54 deletions(-) diff --git a/src/librustc_builtin_macros/deriving/mod.rs b/src/librustc_builtin_macros/deriving/mod.rs index 5ba9d3800e11..b5ad67abf620 100644 --- a/src/librustc_builtin_macros/deriving/mod.rs +++ b/src/librustc_builtin_macros/deriving/mod.rs @@ -2,7 +2,7 @@ use rustc_ast::ast::{self, ItemKind, MetaItem}; use rustc_ast::ptr::P; -use rustc_expand::base::{Annotatable, ExtCtxt, MultiItemModifier}; +use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, MultiItemModifier}; use rustc_span::symbol::{sym, Symbol}; use rustc_span::Span; @@ -48,13 +48,13 @@ impl MultiItemModifier for BuiltinDerive { span: Span, meta_item: &MetaItem, item: Annotatable, - ) -> Vec { + ) -> ExpandResult, Annotatable> { // FIXME: Built-in derives often forget to give spans contexts, // so we are doing it here in a centralized way. let span = ecx.with_def_site_ctxt(span); let mut items = Vec::new(); (self.0)(ecx, span, meta_item, &item, &mut |a| items.push(a)); - items + ExpandResult::Ready(items) } } diff --git a/src/librustc_expand/base.rs b/src/librustc_expand/base.rs index 55e9c70d6373..3782746a57de 100644 --- a/src/librustc_expand/base.rs +++ b/src/librustc_expand/base.rs @@ -258,8 +258,17 @@ impl Annotatable { } } -// `meta_item` is the annotation, and `item` is the item being modified. -// FIXME Decorators should follow the same pattern too. +/// Result of an expansion that may need to be retried. +/// Consider using this for non-`MultiItemModifier` expanders as well. +pub enum ExpandResult { + /// Expansion produced a result (possibly dummy). + Ready(T), + /// Expansion could not produce a result and needs to be retried. + /// The string is an explanation that will be printed if we are stuck in an infinite retry loop. + Retry(U, String), +} + +// `meta_item` is the attribute, and `item` is the item being modified. pub trait MultiItemModifier { fn expand( &self, @@ -267,7 +276,7 @@ pub trait MultiItemModifier { span: Span, meta_item: &ast::MetaItem, item: Annotatable, - ) -> Vec; + ) -> ExpandResult, Annotatable>; } impl MultiItemModifier for F @@ -280,8 +289,8 @@ where span: Span, meta_item: &ast::MetaItem, item: Annotatable, - ) -> Vec { - self(ecx, span, meta_item, item) + ) -> ExpandResult, Annotatable> { + ExpandResult::Ready(self(ecx, span, meta_item, item)) } } diff --git a/src/librustc_expand/expand.rs b/src/librustc_expand/expand.rs index effa89e8bfb2..f2af6755517f 100644 --- a/src/librustc_expand/expand.rs +++ b/src/librustc_expand/expand.rs @@ -408,7 +408,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> { let mut undetermined_invocations = Vec::new(); let (mut progress, mut force) = (false, !self.monotonic); loop { - let invoc = if let Some(invoc) = invocations.pop() { + let (invoc, res) = if let Some(invoc) = invocations.pop() { invoc } else { self.resolve_imports(); @@ -420,30 +420,51 @@ impl<'a, 'b> MacroExpander<'a, 'b> { continue; }; - let eager_expansion_root = - if self.monotonic { invoc.expansion_data.id } else { orig_expansion_data.id }; - let res = match self.cx.resolver.resolve_macro_invocation( - &invoc, - eager_expansion_root, - force, - ) { - Ok(res) => res, - Err(Indeterminate) => { - undetermined_invocations.push(invoc); - continue; + let res = match res { + Some(res) => res, + None => { + let eager_expansion_root = if self.monotonic { + invoc.expansion_data.id + } else { + orig_expansion_data.id + }; + match self.cx.resolver.resolve_macro_invocation( + &invoc, + eager_expansion_root, + force, + ) { + Ok(res) => res, + Err(Indeterminate) => { + // Cannot resolve, will retry this invocation later. + undetermined_invocations.push((invoc, None)); + continue; + } + } } }; - progress = true; let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data; self.cx.current_expansion = invoc.expansion_data.clone(); // FIXME(jseyfried): Refactor out the following logic let (expanded_fragment, new_invocations) = match res { - InvocationRes::Single(ext) => { - let fragment = self.expand_invoc(invoc, &ext.kind); - self.collect_invocations(fragment, &[]) - } + InvocationRes::Single(ext) => match self.expand_invoc(invoc, &ext.kind) { + ExpandResult::Ready(fragment) => self.collect_invocations(fragment, &[]), + ExpandResult::Retry(invoc, explanation) => { + if force { + // We are stuck, stop retrying and produce a dummy fragment. + let span = invoc.span(); + self.cx.span_err(span, &explanation); + let fragment = invoc.fragment_kind.dummy(span); + self.collect_invocations(fragment, &[]) + } else { + // Cannot expand, will retry this invocation later. + undetermined_invocations + .push((invoc, Some(InvocationRes::Single(ext)))); + continue; + } + } + }, InvocationRes::DeriveContainer(_exts) => { // FIXME: Consider using the derive resolutions (`_exts`) immediately, // instead of enqueuing the derives to be resolved again later. @@ -463,14 +484,17 @@ impl<'a, 'b> MacroExpander<'a, 'b> { for path in derives { let expn_id = ExpnId::fresh(None); derive_placeholders.push(NodeId::placeholder_from_expn_id(expn_id)); - invocations.push(Invocation { - kind: InvocationKind::Derive { path, item: item.clone() }, - fragment_kind: invoc.fragment_kind, - expansion_data: ExpansionData { - id: expn_id, - ..invoc.expansion_data.clone() + invocations.push(( + Invocation { + kind: InvocationKind::Derive { path, item: item.clone() }, + fragment_kind: invoc.fragment_kind, + expansion_data: ExpansionData { + id: expn_id, + ..invoc.expansion_data.clone() + }, }, - }); + None, + )); } let fragment = invoc.fragment_kind.expect_from_annotatables(::std::iter::once(item)); @@ -478,6 +502,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> { } }; + progress = true; if expanded_fragments.len() < depth { expanded_fragments.push(Vec::new()); } @@ -535,7 +560,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> { &mut self, mut fragment: AstFragment, extra_placeholders: &[NodeId], - ) -> (AstFragment, Vec) { + ) -> (AstFragment, Vec<(Invocation, Option)>) { // Resolve `$crate`s in the fragment for pretty-printing. self.cx.resolver.resolve_dollar_crates(); @@ -635,13 +660,17 @@ impl<'a, 'b> MacroExpander<'a, 'b> { self.cx.trace_macros_diag(); } - fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtensionKind) -> AstFragment { + fn expand_invoc( + &mut self, + invoc: Invocation, + ext: &SyntaxExtensionKind, + ) -> ExpandResult { if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit { self.error_recursion_limit_reached(); } let (fragment_kind, span) = (invoc.fragment_kind, invoc.span()); - match invoc.kind { + ExpandResult::Ready(match invoc.kind { InvocationKind::Bang { mac, .. } => match ext { SyntaxExtensionKind::Bang(expander) => { self.gate_proc_macro_expansion_kind(span, fragment_kind); @@ -663,7 +692,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> { } _ => unreachable!(), }, - InvocationKind::Attr { attr, mut item, .. } => match ext { + InvocationKind::Attr { attr, mut item, derives, after_derive } => match ext { SyntaxExtensionKind::Attr(expander) => { self.gate_proc_macro_input(&item); self.gate_proc_macro_attr_item(span, &item); @@ -679,8 +708,25 @@ impl<'a, 'b> MacroExpander<'a, 'b> { SyntaxExtensionKind::LegacyAttr(expander) => { match validate_attr::parse_meta(self.cx.parse_sess, &attr) { Ok(meta) => { - let item = expander.expand(self.cx, span, &meta, item); - fragment_kind.expect_from_annotatables(item) + let items = match expander.expand(self.cx, span, &meta, item) { + ExpandResult::Ready(items) => items, + ExpandResult::Retry(item, explanation) => { + // Reassemble the original invocation for retrying. + return ExpandResult::Retry( + Invocation { + kind: InvocationKind::Attr { + attr, + item, + derives, + after_derive, + }, + ..invoc + }, + explanation, + ); + } + }; + fragment_kind.expect_from_annotatables(items) } Err(mut err) => { err.emit(); @@ -702,19 +748,31 @@ impl<'a, 'b> MacroExpander<'a, 'b> { SyntaxExtensionKind::Derive(expander) | SyntaxExtensionKind::LegacyDerive(expander) => { if !item.derive_allowed() { - return fragment_kind.dummy(span); + return ExpandResult::Ready(fragment_kind.dummy(span)); } if let SyntaxExtensionKind::Derive(..) = ext { self.gate_proc_macro_input(&item); } let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path }; - let items = expander.expand(self.cx, span, &meta, item); + let items = match expander.expand(self.cx, span, &meta, item) { + ExpandResult::Ready(items) => items, + ExpandResult::Retry(item, explanation) => { + // Reassemble the original invocation for retrying. + return ExpandResult::Retry( + Invocation { + kind: InvocationKind::Derive { path: meta.path, item }, + ..invoc + }, + explanation, + ); + } + }; fragment_kind.expect_from_annotatables(items) } _ => unreachable!(), }, InvocationKind::DeriveContainer { .. } => unreachable!(), - } + }) } fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) { @@ -933,7 +991,7 @@ pub fn ensure_complete_parse<'a>( struct InvocationCollector<'a, 'b> { cx: &'a mut ExtCtxt<'b>, cfg: StripUnconfigured<'a>, - invocations: Vec, + invocations: Vec<(Invocation, Option)>, monotonic: bool, } @@ -955,15 +1013,18 @@ impl<'a, 'b> InvocationCollector<'a, 'b> { }; let expn_id = ExpnId::fresh(expn_data); let vis = kind.placeholder_visibility(); - self.invocations.push(Invocation { - kind, - fragment_kind, - expansion_data: ExpansionData { - id: expn_id, - depth: self.cx.current_expansion.depth + 1, - ..self.cx.current_expansion.clone() + self.invocations.push(( + Invocation { + kind, + fragment_kind, + expansion_data: ExpansionData { + id: expn_id, + depth: self.cx.current_expansion.depth + 1, + ..self.cx.current_expansion.clone() + }, }, - }); + None, + )); placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis) } diff --git a/src/librustc_expand/proc_macro.rs b/src/librustc_expand/proc_macro.rs index 84a546345bb2..cb9afa4cd4f0 100644 --- a/src/librustc_expand/proc_macro.rs +++ b/src/librustc_expand/proc_macro.rs @@ -79,7 +79,7 @@ impl MultiItemModifier for ProcMacroDerive { span: Span, _meta_item: &ast::MetaItem, item: Annotatable, - ) -> Vec { + ) -> ExpandResult, Annotatable> { let item = match item { Annotatable::Arm(..) | Annotatable::Field(..) @@ -99,7 +99,7 @@ impl MultiItemModifier for ProcMacroDerive { "proc-macro derives may only be \ applied to a struct, enum, or union", ); - return Vec::new(); + return ExpandResult::Ready(Vec::new()); } }; match item.kind { @@ -110,7 +110,7 @@ impl MultiItemModifier for ProcMacroDerive { "proc-macro derives may only be \ applied to a struct, enum, or union", ); - return Vec::new(); + return ExpandResult::Ready(Vec::new()); } } @@ -158,7 +158,7 @@ impl MultiItemModifier for ProcMacroDerive { FatalError.raise(); } - items + ExpandResult::Ready(items) } }