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Proper expansion info for for loops and other compiler expanded language items #25318

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May 13, 2015
Merged

Proper expansion info for for loops and other compiler expanded language items #25318

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0d25851
Proper spans for for loop expansion
nrc May 6, 2015
edb2ee5
Tests
nrc May 12, 2015
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4 changes: 3 additions & 1 deletion src/libsyntax/codemap.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -235,7 +235,9 @@ pub enum MacroFormat {
/// e.g. #[derive(...)] <item>
MacroAttribute,
/// e.g. `format!()`
MacroBang
MacroBang,
/// Expansion performed by the compiler (libsyntax::expand).
CompilerExpansion,
}

#[derive(Clone, Hash, Debug)]
Expand Down
11 changes: 7 additions & 4 deletions src/libsyntax/diagnostic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -770,12 +770,15 @@ fn print_macro_backtrace(w: &mut EmitterWriter,
|span| cm.span_to_string(span));
let (pre, post) = match ei.callee.format {
codemap::MacroAttribute => ("#[", "]"),
codemap::MacroBang => ("", "!")
codemap::MacroBang => ("", "!"),
codemap::CompilerExpansion => ("", ""),
};
try!(print_diagnostic(w, &ss, Note,
&format!("in expansion of {}{}{}", pre,
ei.callee.name,
post), None));
&format!("in expansion of {}{}{}",
pre,
ei.callee.name,
post),
None));
let ss = cm.span_to_string(ei.call_site);
try!(print_diagnostic(w, &ss, Note, "expansion site", None));
Ok(Some(ei.call_site))
Expand Down
51 changes: 42 additions & 9 deletions src/libsyntax/ext/expand.rs
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Expand Up @@ -19,7 +19,7 @@ use ext::build::AstBuilder;
use attr;
use attr::AttrMetaMethods;
use codemap;
use codemap::{Span, Spanned, ExpnInfo, NameAndSpan, MacroBang, MacroAttribute};
use codemap::{Span, Spanned, ExpnInfo, NameAndSpan, MacroBang, MacroAttribute, CompilerExpansion};
use ext::base::*;
use feature_gate::{self, Features};
use fold;
Expand All @@ -34,6 +34,18 @@ use visit::Visitor;
use std_inject;

pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
fn push_compiler_expansion(fld: &mut MacroExpander, span: Span, expansion_desc: &str) {
fld.cx.bt_push(ExpnInfo {
call_site: span,
callee: NameAndSpan {
name: expansion_desc.to_string(),
format: CompilerExpansion,
allow_internal_unstable: true,
span: None,
},
});
}

e.and_then(|ast::Expr {id, node, span}| match node {
// expr_mac should really be expr_ext or something; it's the
// entry-point for all syntax extensions.
Expand Down Expand Up @@ -77,6 +89,8 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
// }
// }

push_compiler_expansion(fld, span, "while let expansion");

// `<pat> => <body>`
let pat_arm = {
let body_expr = fld.cx.expr_block(body);
Expand All @@ -98,7 +112,9 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
// `[opt_ident]: loop { ... }`
let loop_block = fld.cx.block_expr(match_expr);
let (loop_block, opt_ident) = expand_loop_block(loop_block, opt_ident, fld);
fld.cx.expr(span, ast::ExprLoop(loop_block, opt_ident))
let result = fld.cx.expr(span, ast::ExprLoop(loop_block, opt_ident));
fld.cx.bt_pop();
result
}

// Desugar ExprIfLet
Expand All @@ -112,6 +128,8 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
// _ => [<elseopt> | ()]
// }

push_compiler_expansion(fld, span, "if let expansion");

// `<pat> => <body>`
let pat_arm = {
let body_expr = fld.cx.expr_block(body);
Expand Down Expand Up @@ -173,13 +191,16 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
ast::MatchSource::IfLetDesugar {
contains_else_clause: contains_else_clause,
}));
fld.fold_expr(match_expr)
let result = fld.fold_expr(match_expr);
fld.cx.bt_pop();
result
}

// Desugar support for ExprIfLet in the ExprIf else position
ast::ExprIf(cond, blk, elseopt) => {
let elseopt = elseopt.map(|els| els.and_then(|els| match els.node {
ast::ExprIfLet(..) => {
push_compiler_expansion(fld, span, "if let expansion");
// wrap the if-let expr in a block
let span = els.span;
let blk = P(ast::Block {
Expand All @@ -189,7 +210,9 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
rules: ast::DefaultBlock,
span: span
});
fld.cx.expr_block(blk)
let result = fld.cx.expr_block(blk);
fld.cx.bt_pop();
result
}
_ => P(els)
}));
Expand Down Expand Up @@ -221,6 +244,10 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
// result
// }

push_compiler_expansion(fld, span, "for loop expansion");

let span = fld.new_span(span);

// expand <head>
let head = fld.fold_expr(head);

Expand All @@ -235,10 +262,11 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
rename_fld.fold_ident(ident)
};

let pat_span = pat.span;
// `:;std::option::Option::Some(<pat>) => <body>`
let pat_span = fld.new_span(pat.span);
// `::std::option::Option::Some(<pat>) => <body>`
let pat_arm = {
let body_expr = fld.cx.expr_block(body);
let pat = noop_fold_pat(pat, fld);
let some_pat = fld.cx.pat_some(pat_span, pat);

fld.cx.arm(pat_span, vec![some_pat], body_expr)
Expand Down Expand Up @@ -304,20 +332,25 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {

// `{ let result = ...; result }`
let result_ident = token::gensym_ident("result");
fld.cx.expr_block(
let result = fld.cx.expr_block(
fld.cx.block_all(
span,
vec![fld.cx.stmt_let(span, false, result_ident, match_expr)],
Some(fld.cx.expr_ident(span, result_ident))))
Some(fld.cx.expr_ident(span, result_ident))));
fld.cx.bt_pop();
result
}

ast::ExprClosure(capture_clause, fn_decl, block) => {
push_compiler_expansion(fld, span, "closure expansion");
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Came here from git blame, was this change accidental?
Closures are not expanded differently from free functions, so they shouldn't require custom expansion stacks.
All that does is pollute diagnostic output IMO.

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Yeah, probably wrong

let (rewritten_fn_decl, rewritten_block)
= expand_and_rename_fn_decl_and_block(fn_decl, block, fld);
let new_node = ast::ExprClosure(capture_clause,
rewritten_fn_decl,
rewritten_block);
P(ast::Expr{id:id, node: new_node, span: fld.new_span(span)})
let result = P(ast::Expr{id:id, node: new_node, span: fld.new_span(span)});
fld.cx.bt_pop();
result
}

_ => {
Expand Down
18 changes: 18 additions & 0 deletions src/test/compile-fail/for-expn-2.rs
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@@ -0,0 +1,18 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Test that we get an expansion stack for `for` loops.

// error-pattern:in expansion of for loop expansion

fn main() {
for t in &foo {
}
}
19 changes: 19 additions & 0 deletions src/test/compile-fail/for-expn.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Test that an error on a sub-expresson in a for loop has the correct span.

fn main() {
// Odd formatting to make sure we get the right span.
for t in &
foo //~ ERROR unresolved name `foo`
{
}
}