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Allow skipping extra paren insertion during AST pretty-printing

Browse source 
Fixes #74616
Makes progress towards #43081
Unblocks PR #76130

When pretty-printing an AST node, we may insert additional parenthesis
to ensure that precedence is properly preserved in code we output.
However, the proc macro implementation relies on comparing a
pretty-printed AST node to the captured `TokenStream`. Inserting extra
parenthesis changes the structure of the reparsed `TokenStream`, making
the comparison fail.

This PR refactors the AST pretty-printing code to allow skipping the
insertion of additional parenthesis. Several freestanding methods are
moved to trait methods on `PrintState`, which keep track of an internal
`insert_extra_parens` flag. This flag is normally `true`, but we expose
a public method which allows pretty-printing a nonterminal with
`insert_extra_parens = false`.

To avoid changing the public interface of `rustc_ast_pretty`, the
freestanding `_to_string` methods are changed to delegate to a
newly-crated `State`. The main pretty-printing code is moved to a new
`state` module to ensure that it does not accidentally call any of these
public helper functions (instead, the internal functions with the same
name should be used).
This commit is contained in:
Aaron Hill 2020-09-26 12:51:00 -04:00
parent a20ae8901c
commit ea468f4270
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GPG key ID: B4087E510E98B164
6 changed files with 219 additions and 12 deletions
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26
src/test/ui/proc-macro/issue-75734-pp-paren.rs Normal file
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@ -0,0 +1,26 @@
// Regression test for issue #75734
// Ensures that we don't lose tokens when pretty-printing would
// normally insert extra parentheses.
// check-pass
// aux-build:test-macros.rs
// compile-flags: -Z span-debug
#![no_std] // Don't load unnecessary hygiene information from std
extern crate std;
#[macro_use]
extern crate test_macros;
macro_rules! mul_2 {
($val:expr) => {
print_bang!($val * 2);
};
}
#[print_attr]
fn main() {
&|_: u8| {};
mul_2!(1 + 1);
}

134
src/test/ui/proc-macro/issue-75734-pp-paren.stdout Normal file
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PRINT-ATTR INPUT (DISPLAY): fn main() { & | _ : u8 | { } ; mul_2 ! (1 + 1) ; }
PRINT-ATTR INPUT (DEBUG): TokenStream [
Ident {
ident: "fn",
span: $DIR/issue-75734-pp-paren.rs:23:1: 23:3 (#0),
},
Ident {
ident: "main",
span: $DIR/issue-75734-pp-paren.rs:23:4: 23:8 (#0),
},
Group {
delimiter: Parenthesis,
stream: TokenStream [],
span: $DIR/issue-75734-pp-paren.rs:23:8: 23:10 (#0),
},
Group {
delimiter: Brace,
stream: TokenStream [
Punct {
ch: '&',
spacing: Joint,
span: $DIR/issue-75734-pp-paren.rs:24:5: 24:6 (#0),
},
Punct {
ch: '|',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:24:6: 24:7 (#0),
},
Ident {
ident: "_",
span: $DIR/issue-75734-pp-paren.rs:24:7: 24:8 (#0),
},
Punct {
ch: ':',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:24:8: 24:9 (#0),
},
Ident {
ident: "u8",
span: $DIR/issue-75734-pp-paren.rs:24:10: 24:12 (#0),
},
Punct {
ch: '|',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:24:12: 24:13 (#0),
},
Group {
delimiter: Brace,
stream: TokenStream [],
span: $DIR/issue-75734-pp-paren.rs:24:14: 24:16 (#0),
},
Punct {
ch: ';',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:24:16: 24:17 (#0),
},
Ident {
ident: "mul_2",
span: $DIR/issue-75734-pp-paren.rs:25:5: 25:10 (#0),
},
Punct {
ch: '!',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:25:10: 25:11 (#0),
},
Group {
delimiter: Parenthesis,
stream: TokenStream [
Literal {
kind: Integer,
symbol: "1",
suffix: None,
span: $DIR/issue-75734-pp-paren.rs:25:12: 25:13 (#0),
},
Punct {
ch: '+',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:25:14: 25:15 (#0),
},
Literal {
kind: Integer,
symbol: "1",
suffix: None,
span: $DIR/issue-75734-pp-paren.rs:25:16: 25:17 (#0),
},
],
span: $DIR/issue-75734-pp-paren.rs:25:11: 25:18 (#0),
},
Punct {
ch: ';',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:25:18: 25:19 (#0),
},
],
span: $DIR/issue-75734-pp-paren.rs:23:11: 26:2 (#0),
},
]
PRINT-BANG INPUT (DISPLAY): 1 + 1 * 2
PRINT-BANG INPUT (DEBUG): TokenStream [
Group {
delimiter: None,
stream: TokenStream [
Literal {
kind: Integer,
symbol: "1",
suffix: None,
span: $DIR/issue-75734-pp-paren.rs:25:12: 25:13 (#0),
},
Punct {
ch: '+',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:25:14: 25:15 (#0),
},
Literal {
kind: Integer,
symbol: "1",
suffix: None,
span: $DIR/issue-75734-pp-paren.rs:25:16: 25:17 (#0),
},
],
span: $DIR/issue-75734-pp-paren.rs:17:21: 17:25 (#7),
},
Punct {
ch: '*',
spacing: Alone,
span: $DIR/issue-75734-pp-paren.rs:17:26: 17:27 (#7),
},
Literal {
kind: Integer,
symbol: "2",
suffix: None,
span: $DIR/issue-75734-pp-paren.rs:17:28: 17:29 (#7),
},
]