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Auto merge of #78088 - fusion-engineering-forks:panic-fmt-lint, r=estebank

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Add lint for panic!("{}")

This adds a lint that warns about `panic!("{}")`.

`panic!(msg)` invocations with a single argument use their argument as panic payload literally, without using it as a format string. The same holds for `assert!(expr, msg)`.

This lints checks if `msg` is a string literal (after expansion), and warns in case it contained braces. It suggests to insert `"{}", ` to use the message literally, or to add arguments to use it as a format string.

![image](https://user-images.githubusercontent.com/783247/96643867-79eb1080-1328-11eb-8d4e-a5586837c70a.png)

This lint is also a good starting point for adding warnings about `panic!(not_a_string)` later, once [`panic_any()`](https://github.com/rust-lang/rust/pull/74622) becomes a stable alternative.
This commit is contained in:
bors 2020-11-20 03:40:20 +00:00
commit 74285eb3a8
22 changed files with 362 additions and 165 deletions
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52
compiler/rustc_builtin_macros/src/assert.rs
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@ -1,8 +1,8 @@
use rustc_errors::{Applicability, DiagnosticBuilder};
use rustc_ast::ptr::P;
use rustc_ast::token::{self, TokenKind};
use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
use rustc_ast::token;
use rustc_ast::tokenstream::{DelimSpan, TokenStream};
use rustc_ast::{self as ast, *};
use rustc_ast_pretty::pprust;
use rustc_expand::base::*;
@ -26,31 +26,39 @@ pub fn expand_assert<'cx>(
// `core::panic` and `std::panic` are different macros, so we use call-site
// context to pick up whichever is currently in scope.
let sp = cx.with_call_site_ctxt(sp);
let tokens = custom_message.unwrap_or_else(|| {
TokenStream::from(TokenTree::token(
TokenKind::lit(
token::Str,
let panic_call = if let Some(tokens) = custom_message {
// Pass the custom message to panic!().
cx.expr(
sp,
ExprKind::MacCall(MacCall {
path: Path::from_ident(Ident::new(sym::panic, sp)),
args: P(MacArgs::Delimited(
DelimSpan::from_single(sp),
MacDelimiter::Parenthesis,
tokens,
)),
prior_type_ascription: None,
}),
)
} else {
// Pass our own message directly to $crate::panicking::panic(),
// because it might contain `{` and `}` that should always be
// passed literally.
cx.expr_call_global(
sp,
cx.std_path(&[sym::panicking, sym::panic]),
vec![cx.expr_str(
DUMMY_SP,
Symbol::intern(&format!(
"assertion failed: {}",
pprust::expr_to_string(&cond_expr).escape_debug()
)),
None,
),
DUMMY_SP,
))
});
let args = P(MacArgs::Delimited(DelimSpan::from_single(sp), MacDelimiter::Parenthesis, tokens));
let panic_call = MacCall {
path: Path::from_ident(Ident::new(sym::panic, sp)),
args,
prior_type_ascription: None,
)],
)
};
let if_expr = cx.expr_if(
sp,
cx.expr(sp, ExprKind::Unary(UnOp::Not, cond_expr)),
cx.expr(sp, ExprKind::MacCall(panic_call)),
None,
);
let if_expr =
cx.expr_if(sp, cx.expr(sp, ExprKind::Unary(UnOp::Not, cond_expr)), panic_call, None);
MacEager::expr(if_expr)
}