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Auto merge of #29727 - alexcrichton:debug-unused-result, r=sfackler

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This should help avoid triggering the unused_results lint which can frequently
be turned on.

Closes #29710
This commit is contained in:
bors
2015-11-11 02:08:08 +00:00
parent ad3bd1b46d 5d55533f93
commit dbb78549aa
2 changed files with 41 additions and 4 deletions
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25
src/libsyntax/ext/deriving/debug.rs
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@@ -9,8 +9,8 @@
// except according to those terms.
use ast;
use ast::{MetaItem, Expr,};
use codemap::Span;
use ast::{MetaItem, Expr};
use codemap::{Span, respan};
use ext::base::{ExtCtxt, Annotatable};
use ext::build::AstBuilder;
use ext::deriving::generic::*;
@@ -97,7 +97,10 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span,
builder_expr.clone(),
token::str_to_ident("field"),
vec![field]);
stmts.push(cx.stmt_expr(expr));
// Use `let _ = expr;` to avoid triggering the
// unused_results lint.
stmts.push(stmt_let_undescore(cx, span, expr));
}
} else {
// normal struct/struct variant
@@ -119,7 +122,7 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span,
builder_expr.clone(),
token::str_to_ident("field"),
vec![name, field]);
stmts.push(cx.stmt_expr(expr));
stmts.push(stmt_let_undescore(cx, span, expr));
}
}
stmts
@@ -135,3 +138,17 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span,
let block = cx.block(span, stmts, Some(expr));
cx.expr_block(block)
}
fn stmt_let_undescore(cx: &mut ExtCtxt,
sp: Span,
expr: P<ast::Expr>) -> P<ast::Stmt> {
let local = P(ast::Local {
pat: cx.pat_wild(sp),
ty: None,
init: Some(expr),
id: ast::DUMMY_NODE_ID,
span: sp,
});
let decl = respan(sp, ast::DeclLocal(local));
P(respan(sp, ast::StmtDecl(P(decl), ast::DUMMY_NODE_ID)))
}