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Rollup merge of rust-lang#71322 - petrochenkov:tuple00, r=nikomatsakis
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Accept tuple.0.0 as tuple indexing (take 2)

If we expect something identifier-like when parsing a field name after `.`, but encounter a float token, we break that float token into parts, similarly to how we break `&&` into `&` `&`, or `<<` into `<` `<`, etc.

An alternative to rust-lang#70420.
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Manishearth authored Jul 11, 2020
2 parents daecab3 + 52bdaaa commit 81bcee6
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Showing 13 changed files with 614 additions and 59 deletions.
119 changes: 81 additions & 38 deletions src/librustc_parse/parser/expr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -770,10 +770,10 @@ impl<'a> Parser<'a> {
match self.token.uninterpolate().kind {
token::Ident(..) => self.parse_dot_suffix(base, lo),
token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix))
Ok(self.parse_tuple_field_access_expr(lo, base, symbol, suffix, None))
}
token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
self.recover_field_access_by_float_lit(lo, base, symbol)
token::Literal(token::Lit { kind: token::Float, symbol, suffix }) => {
Ok(self.parse_tuple_field_access_expr_float(lo, base, symbol, suffix))
}
_ => {
self.error_unexpected_after_dot();
Expand All @@ -788,45 +788,84 @@ impl<'a> Parser<'a> {
self.struct_span_err(self.token.span, &format!("unexpected token: `{}`", actual)).emit();
}

fn recover_field_access_by_float_lit(
// We need and identifier or integer, but the next token is a float.
// Break the float into components to extract the identifier or integer.
// FIXME: With current `TokenCursor` it's hard to break tokens into more than 2
// parts unless those parts are processed immediately. `TokenCursor` should either
// support pushing "future tokens" (would be also helpful to `break_and_eat`), or
// we should break everything including floats into more basic proc-macro style
// tokens in the lexer (probably preferable).
fn parse_tuple_field_access_expr_float(
&mut self,
lo: Span,
base: P<Expr>,
sym: Symbol,
) -> PResult<'a, P<Expr>> {
self.bump();

let fstr = sym.as_str();
let msg = format!("unexpected token: `{}`", sym);

let mut err = self.struct_span_err(self.prev_token.span, &msg);
err.span_label(self.prev_token.span, "unexpected token");

if fstr.chars().all(|x| "0123456789.".contains(x)) {
let float = match fstr.parse::<f64>() {
Ok(f) => f,
Err(_) => {
err.emit();
return Ok(base);
float: Symbol,
suffix: Option<Symbol>,
) -> P<Expr> {
#[derive(Debug)]
enum FloatComponent {
IdentLike(String),
Punct(char),
}
use FloatComponent::*;

let mut components = Vec::new();
let mut ident_like = String::new();
for c in float.as_str().chars() {
if c == '_' || c.is_ascii_alphanumeric() {
ident_like.push(c);
} else if matches!(c, '.' | '+' | '-') {
if !ident_like.is_empty() {
components.push(IdentLike(mem::take(&mut ident_like)));
}
};
let sugg = pprust::to_string(|s| {
s.popen();
s.print_expr(&base);
s.s.word(".");
s.print_usize(float.trunc() as usize);
s.pclose();
s.s.word(".");
s.s.word(fstr.splitn(2, '.').last().unwrap().to_string())
});
err.span_suggestion(
lo.to(self.prev_token.span),
"try parenthesizing the first index",
sugg,
Applicability::MachineApplicable,
);
components.push(Punct(c));
} else {
panic!("unexpected character in a float token: {:?}", c)
}
}
if !ident_like.is_empty() {
components.push(IdentLike(ident_like));
}

// FIXME: Make the span more precise.
let span = self.token.span;
match &*components {
// 1e2
[IdentLike(i)] => {
self.parse_tuple_field_access_expr(lo, base, Symbol::intern(&i), suffix, None)
}
// 1.
[IdentLike(i), Punct('.')] => {
assert!(suffix.is_none());
let symbol = Symbol::intern(&i);
self.token = Token::new(token::Ident(symbol, false), span);
let next_token = Token::new(token::Dot, span);
self.parse_tuple_field_access_expr(lo, base, symbol, None, Some(next_token))
}
// 1.2 | 1.2e3
[IdentLike(i1), Punct('.'), IdentLike(i2)] => {
let symbol1 = Symbol::intern(&i1);
self.token = Token::new(token::Ident(symbol1, false), span);
let next_token1 = Token::new(token::Dot, span);
let base1 =
self.parse_tuple_field_access_expr(lo, base, symbol1, None, Some(next_token1));
let symbol2 = Symbol::intern(&i2);
let next_token2 = Token::new(token::Ident(symbol2, false), span);
self.bump_with(next_token2); // `.`
self.parse_tuple_field_access_expr(lo, base1, symbol2, suffix, None)
}
// 1e+ | 1e- (recovered)
[IdentLike(_), Punct('+' | '-')] |
// 1e+2 | 1e-2
[IdentLike(_), Punct('+' | '-'), IdentLike(_)] |
// 1.2e+3 | 1.2e-3
[IdentLike(_), Punct('.'), IdentLike(_), Punct('+' | '-'), IdentLike(_)] => {
// See the FIXME about `TokenCursor` above.
self.error_unexpected_after_dot();
base
}
_ => panic!("unexpected components in a float token: {:?}", components),
}
Err(err)
}

fn parse_tuple_field_access_expr(
Expand All @@ -835,8 +874,12 @@ impl<'a> Parser<'a> {
base: P<Expr>,
field: Symbol,
suffix: Option<Symbol>,
next_token: Option<Token>,
) -> P<Expr> {
self.bump();
match next_token {
Some(next_token) => self.bump_with(next_token),
None => self.bump(),
}
let span = self.prev_token.span;
let field = ExprKind::Field(base, Ident::new(field, span));
self.expect_no_suffix(span, "a tuple index", suffix);
Expand Down
17 changes: 17 additions & 0 deletions src/test/ui/parser/float-field-interpolated.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
struct S(u8, (u8, u8));

macro_rules! generate_field_accesses {
($a:tt, $b:literal, $c:expr) => {
let s = S(0, (0, 0));

s.$a; // OK
{ s.$b; } //~ ERROR unexpected token: `1.1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1`
{ s.$c; } //~ ERROR unexpected token: `1.1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1`
};
}

fn main() {
generate_field_accesses!(1.1, 1.1, 1.1);
}
46 changes: 46 additions & 0 deletions src/test/ui/parser/float-field-interpolated.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
error: unexpected token: `1.1`
--> $DIR/float-field-interpolated.rs:8:13
|
LL | { s.$b; }
| ^^
...
LL | generate_field_accesses!(1.1, 1.1, 1.1);
| ---------------------------------------- in this macro invocation
|
= note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1`
--> $DIR/float-field-interpolated.rs:8:13
|
LL | { s.$b; }
| ^^ expected one of `.`, `;`, `?`, `}`, or an operator
...
LL | generate_field_accesses!(1.1, 1.1, 1.1);
| ---------------------------------------- in this macro invocation
|
= note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: unexpected token: `1.1`
--> $DIR/float-field-interpolated.rs:10:13
|
LL | { s.$c; }
| ^^
...
LL | generate_field_accesses!(1.1, 1.1, 1.1);
| ---------------------------------------- in this macro invocation
|
= note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1`
--> $DIR/float-field-interpolated.rs:10:13
|
LL | { s.$c; }
| ^^ expected one of `.`, `;`, `?`, `}`, or an operator
...
LL | generate_field_accesses!(1.1, 1.1, 1.1);
| ---------------------------------------- in this macro invocation
|
= note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 4 previous errors

62 changes: 62 additions & 0 deletions src/test/ui/parser/float-field.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,62 @@
struct S(u8, (u8, u8));

fn main() {
let s = S(0, (0, 0));

s.1e1; //~ ERROR no field `1e1` on type `S`
s.1.; //~ ERROR unexpected token: `;`
s.1.1;
s.1.1e1; //~ ERROR no field `1e1` on type `(u8, u8)`
{ s.1e+; } //~ ERROR unexpected token: `1e+`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e+`
//~| ERROR expected at least one digit in exponent
{ s.1e-; } //~ ERROR unexpected token: `1e-`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e-`
//~| ERROR expected at least one digit in exponent
{ s.1e+1; } //~ ERROR unexpected token: `1e+1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e+1`
{ s.1e-1; } //~ ERROR unexpected token: `1e-1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e-1`
{ s.1.1e+1; } //~ ERROR unexpected token: `1.1e+1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1e+1`
{ s.1.1e-1; } //~ ERROR unexpected token: `1.1e-1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1e-1`
s.0x1e1; //~ ERROR no field `0x1e1` on type `S`
s.0x1.; //~ ERROR no field `0x1` on type `S`
//~| ERROR hexadecimal float literal is not supported
//~| ERROR unexpected token: `;`
s.0x1.1; //~ ERROR no field `0x1` on type `S`
//~| ERROR hexadecimal float literal is not supported
s.0x1.1e1; //~ ERROR no field `0x1` on type `S`
//~| ERROR hexadecimal float literal is not supported
{ s.0x1e+; } //~ ERROR expected expression, found `;`
{ s.0x1e-; } //~ ERROR expected expression, found `;`
s.0x1e+1; //~ ERROR no field `0x1e` on type `S`
s.0x1e-1; //~ ERROR no field `0x1e` on type `S`
{ s.0x1.1e+1; } //~ ERROR unexpected token: `0x1.1e+1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `0x1.1e+1`
//~| ERROR hexadecimal float literal is not supported
{ s.0x1.1e-1; } //~ ERROR unexpected token: `0x1.1e-1`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `0x1.1e-1`
//~| ERROR hexadecimal float literal is not supported
s.1e1f32; //~ ERROR no field `1e1` on type `S`
//~| ERROR suffixes on a tuple index are invalid
s.1.f32; //~ ERROR no field `f32` on type `(u8, u8)`
s.1.1f32; //~ ERROR suffixes on a tuple index are invalid
s.1.1e1f32; //~ ERROR no field `1e1` on type `(u8, u8)`
//~| ERROR suffixes on a tuple index are invalid
{ s.1e+f32; } //~ ERROR unexpected token: `1e+f32`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e+f32`
//~| ERROR expected at least one digit in exponent
{ s.1e-f32; } //~ ERROR unexpected token: `1e-f32`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e-f32`
//~| ERROR expected at least one digit in exponent
{ s.1e+1f32; } //~ ERROR unexpected token: `1e+1f32`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e+1f32`
{ s.1e-1f32; } //~ ERROR unexpected token: `1e-1f32`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1e-1f32`
{ s.1.1e+1f32; } //~ ERROR unexpected token: `1.1e+1f32`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1e+1f32`
{ s.1.1e-1f32; } //~ ERROR unexpected token: `1.1e-1f32`
//~| ERROR expected one of `.`, `;`, `?`, `}`, or an operator, found `1.1e-1f32`
}
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