rustc_builtin_macros/
assert.rs

1mod context;
2
3use rustc_ast::token::Delimiter;
4use rustc_ast::tokenstream::TokenStream;
5use rustc_ast::{Expr, ExprKind, Path, UnOp, token};
6use rustc_ast_pretty::pprust;
7use rustc_errors::PResult;
8use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
9use rustc_parse::exp;
10use rustc_parse::parser::Parser;
11use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
12use thin_vec::thin_vec;
13
14use crate::diagnostics;
15use crate::edition_panic::use_panic_2021;
16
17pub(crate) fn expand_assert<'cx>(
18    cx: &'cx mut ExtCtxt<'_>,
19    span: Span,
20    tts: TokenStream,
21) -> MacroExpanderResult<'cx> {
22    let Assert { cond_expr, custom_message } = match parse_assert(cx, span, tts) {
23        Ok(assert) => assert,
24        Err(err) => {
25            let guar = err.emit_err();
26            return ExpandResult::Ready(DummyResult::any(span, guar));
27        }
28    };
29
30    // `core::panic` and `std::panic` are different macros, so we use call-site
31    // context to pick up whichever is currently in scope.
32    let call_site_span = cx.with_call_site_ctxt(span);
33
34    let panic_path = || {
35        if use_panic_2021(span) {
36            // On edition 2021, we always call `$crate::panic::panic_2021!()`.
37            cx.path(call_site_span, cx.std_path(&[sym::panic, sym::panic_2021]))
38        } else {
39            // Before edition 2021, we call `panic!()` unqualified,
40            // such that it calls either `std::panic!()` or `core::panic!()`.
41            Path::from_ident(Ident::new(sym::panic, call_site_span))
42        }
43    };
44
45    // Simply uses the user provided message instead of generating custom outputs
46    let expr = if let Some(tokens) = custom_message {
47        let then = cx.expr_macro_call(
48            call_site_span,
49            cx.macro_call(call_site_span, panic_path(), Delimiter::Parenthesis, tokens),
50        );
51        expr_if_not(cx, call_site_span, cond_expr, then, None)
52    }
53    // If `generic_assert` is enabled, generates rich captured outputs
54    //
55    // FIXME(c410-f3r) See https://github.com/rust-lang/rust/issues/96949
56    else if cx.ecfg.features.generic_assert() {
57        context::Context::new(cx, call_site_span).build(cond_expr, panic_path())
58    }
59    // If `generic_assert` is not enabled, only outputs a literal "assertion failed: ..."
60    // string
61    else {
62        // Pass our own message directly to $crate::panicking::panic(),
63        // because it might contain `{` and `}` that should always be
64        // passed literally.
65        let then = cx.expr_call_global(
66            call_site_span,
67            cx.std_path(&[sym::panicking, sym::panic]),
68            {
    let len = [()].len();
    let mut vec = ::thin_vec::ThinVec::with_capacity(len);
    vec.push(cx.expr_str(DUMMY_SP,
            Symbol::intern(&::alloc::__export::must_use({
                            ::alloc::fmt::format(format_args!("assertion failed: {0}",
                                    pprust::expr_to_string(&cond_expr)))
                        }))));
    vec
}thin_vec![cx.expr_str(
69                DUMMY_SP,
70                Symbol::intern(&format!(
71                    "assertion failed: {}",
72                    pprust::expr_to_string(&cond_expr)
73                )),
74            )],
75        );
76        expr_if_not(cx, call_site_span, cond_expr, then, None)
77    };
78
79    ExpandResult::Ready(MacEager::expr(expr))
80}
81
82struct Assert {
83    cond_expr: Box<Expr>,
84    custom_message: Option<TokenStream>,
85}
86
87// if !{ ... } { ... } else { ... }
88fn expr_if_not(
89    cx: &ExtCtxt<'_>,
90    span: Span,
91    cond: Box<Expr>,
92    then: Box<Expr>,
93    els: Option<Box<Expr>>,
94) -> Box<Expr> {
95    cx.expr_if(span, cx.expr(span, ExprKind::Unary(UnOp::Not, cond)), then, els)
96}
97
98fn parse_assert<'a>(cx: &ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PResult<'a, Assert> {
99    let mut parser = cx.new_parser_from_tts(stream);
100
101    if parser.token == token::Eof {
102        return Err(cx.dcx().create_err(diagnostics::AssertRequiresBoolean { span: sp }));
103    }
104
105    let cond_expr = parser.parse_expr()?;
106
107    // Some crates use the `assert!` macro in the following form (note extra semicolon):
108    //
109    // assert!(
110    //     my_function();
111    // );
112    //
113    // Emit an error about semicolon and suggest removing it.
114    if parser.token == token::Semi {
115        cx.dcx()
116            .emit_err(diagnostics::AssertRequiresExpression { span: sp, token: parser.token.span });
117        parser.bump();
118    }
119
120    // Some crates use the `assert!` macro in the following form (note missing comma before
121    // message):
122    //
123    // assert!(true "error message");
124    //
125    // Emit an error and suggest inserting a comma.
126    let custom_message =
127        if let token::Literal(token::Lit { kind: token::Str, .. }) = parser.token.kind {
128            let comma = parser.prev_token.span.shrink_to_hi();
129            cx.dcx().emit_err(diagnostics::AssertMissingComma { span: parser.token.span, comma });
130
131            parse_custom_message(&mut parser)
132        } else if parser.eat(::rustc_parse::parser::token_type::ExpTokenPair {
    tok: rustc_ast::token::Comma,
    token_type: ::rustc_parse::parser::token_type::TokenType::Comma,
}exp!(Comma)) {
133            parse_custom_message(&mut parser)
134        } else {
135            None
136        };
137
138    if parser.token != token::Eof {
139        parser.unexpected()?;
140    }
141
142    Ok(Assert { cond_expr, custom_message })
143}
144
145fn parse_custom_message(parser: &mut Parser<'_>) -> Option<TokenStream> {
146    let ts = parser.parse_tokens();
147    if !ts.is_empty() { Some(ts) } else { None }
148}
rustc_builtin_macros/assert.rs

rustc_builtin_macros/
assert.rs
