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Rollup merge of #91607 - FabianWolff:issue-91560-const-span, r=jackh726

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Make `span_extend_to_prev_str()` more robust

Fixes #91560. The logic in `span_extend_to_prev_str()` is currently quite brittle and fails if there is extra whitespace or something else in between, and it also should return an `Option` but doesn't currently.
This commit is contained in:
Matthias Krüger 2022-02-11 21:48:43 +01:00 • committed by GitHub
commit b7c48b4691
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7 changed files with 123 additions and 46 deletions
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38
compiler/rustc_resolve/src/diagnostics.rs
View file

@ -453,28 +453,28 @@ impl<'a> Resolver<'a> {
// edit:
// only do this if the const and usage of the non-constant value are on the same line
// the further the two are apart, the higher the chance of the suggestion being wrong
// also make sure that the pos for the suggestion is not 0 (ICE #90878)
let sp =
self.session.source_map().span_extend_to_prev_str(ident.span, current, true);
let sp = self
.session
.source_map()
.span_extend_to_prev_str(ident.span, current, true, false);
let pos_for_suggestion = sp.lo().0.saturating_sub(current.len() as u32);
if sp.lo().0 == 0
|| pos_for_suggestion == 0
|| self.session.source_map().is_multiline(sp)
{
err.span_label(ident.span, &format!("this would need to be a `{}`", sugg));
} else {
let sp = sp.with_lo(BytePos(pos_for_suggestion));
err.span_suggestion(
sp,
&format!("consider using `{}` instead of `{}`", sugg, current),
format!("{} {}", sugg, ident),
Applicability::MaybeIncorrect,
);
err.span_label(span, "non-constant value");
match sp {
Some(sp) if !self.session.source_map().is_multiline(sp) => {
let sp = sp.with_lo(BytePos(sp.lo().0 - (current.len() as u32)));
err.span_suggestion(
sp,
&format!("consider using `{}` instead of `{}`", sugg, current),
format!("{} {}", sugg, ident),
Applicability::MaybeIncorrect,
);
err.span_label(span, "non-constant value");
}
_ => {
err.span_label(ident.span, &format!("this would need to be a `{}`", sugg));
}
}
err
}
ResolutionError::BindingShadowsSomethingUnacceptable {

40
compiler/rustc_span/src/source_map.rs
View file

@ -629,26 +629,41 @@ impl SourceMap {
}
/// Extends the given `Span` to just after the previous occurrence of `pat` when surrounded by
/// whitespace. Returns the same span if no character could be found or if an error occurred
/// while retrieving the code snippet.
pub fn span_extend_to_prev_str(&self, sp: Span, pat: &str, accept_newlines: bool) -> Span {
/// whitespace. Returns None if the pattern could not be found or if an error occurred while
/// retrieving the code snippet.
pub fn span_extend_to_prev_str(
&self,
sp: Span,
pat: &str,
accept_newlines: bool,
include_whitespace: bool,
) -> Option<Span> {
// assure that the pattern is delimited, to avoid the following
// fn my_fn()
// ^^^^ returned span without the check
// ---------- correct span
let prev_source = self.span_to_prev_source(sp).ok()?;
for ws in &[" ", "\t", "\n"] {
let pat = pat.to_owned() + ws;
if let Ok(prev_source) = self.span_to_prev_source(sp) {
let prev_source = prev_source.rsplit(&pat).next().unwrap_or("").trim_start();
if prev_source.is_empty() && sp.lo().0 != 0 {
return sp.with_lo(BytePos(sp.lo().0 - 1));
} else if accept_newlines || !prev_source.contains('\n') {
return sp.with_lo(BytePos(sp.lo().0 - prev_source.len() as u32));
if let Some(pat_pos) = prev_source.rfind(&pat) {
let just_after_pat_pos = pat_pos + pat.len() - 1;
let just_after_pat_plus_ws = if include_whitespace {
just_after_pat_pos
+ prev_source[just_after_pat_pos..]
.find(|c: char| !c.is_whitespace())
.unwrap_or(0)
} else {
just_after_pat_pos
};
let len = prev_source.len() - just_after_pat_plus_ws;
let prev_source = &prev_source[just_after_pat_plus_ws..];
if accept_newlines || !prev_source.trim_start().contains('\n') {
return Some(sp.with_lo(BytePos(sp.lo().0 - len as u32)));
}
}
}
sp
None
}
/// Returns the source snippet as `String` after the given `Span`.
@ -927,7 +942,7 @@ impl SourceMap {
}
pub fn generate_fn_name_span(&self, span: Span) -> Option<Span> {
let prev_span = self.span_extend_to_prev_str(span, "fn", true);
let prev_span = self.span_extend_to_prev_str(span, "fn", true, true).unwrap_or(span);
if let Ok(snippet) = self.span_to_snippet(prev_span) {
debug!(
"generate_fn_name_span: span={:?}, prev_span={:?}, snippet={:?}",
@ -968,8 +983,7 @@ impl SourceMap {
pub fn generate_local_type_param_snippet(&self, span: Span) -> Option<(Span, String)> {
// Try to extend the span to the previous "fn" keyword to retrieve the function
// signature.
let sugg_span = self.span_extend_to_prev_str(span, "fn", false);
if sugg_span != span {
if let Some(sugg_span) = self.span_extend_to_prev_str(span, "fn", false, true) {
if let Ok(snippet) = self.span_to_snippet(sugg_span) {
// Consume the function name.
let mut offset = snippet

14
src/test/ui/asm/aarch64/parse-error.stderr
View file

@ -382,7 +382,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:39:37
|
LL | let mut foo = 0;
| ---------- help: consider using `const` instead of `let`: `const foo`
| ----------- help: consider using `const` instead of `let`: `const foo`
...
LL | asm!("{}", options(), const foo);
| ^^^ non-constant value
@ -391,7 +391,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:48:44
|
LL | let mut foo = 0;
| ---------- help: consider using `const` instead of `let`: `const foo`
| ----------- help: consider using `const` instead of `let`: `const foo`
...
LL | asm!("{}", clobber_abi("C"), const foo);
| ^^^ non-constant value
@ -400,7 +400,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:55:31
|
LL | let mut foo = 0;
| ---------- help: consider using `const` instead of `let`: `const foo`
| ----------- help: consider using `const` instead of `let`: `const foo`
...
LL | asm!("{a}", a = const foo, a = const bar);
| ^^^ non-constant value
@ -409,7 +409,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:55:46
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{a}", a = const foo, a = const bar);
| ^^^ non-constant value
@ -418,7 +418,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:62:45
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{a}", in("x0") foo, a = const bar);
| ^^^ non-constant value
@ -427,7 +427,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:65:45
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{a}", in("x0") foo, a = const bar);
| ^^^ non-constant value
@ -436,7 +436,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:68:41
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{1}", in("x0") foo, const bar);
| ^^^ non-constant value

14
src/test/ui/asm/x86_64/parse-error.stderr
View file

@ -394,7 +394,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:39:37
|
LL | let mut foo = 0;
| ---------- help: consider using `const` instead of `let`: `const foo`
| ----------- help: consider using `const` instead of `let`: `const foo`
...
LL | asm!("{}", options(), const foo);
| ^^^ non-constant value
@ -403,7 +403,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:50:44
|
LL | let mut foo = 0;
| ---------- help: consider using `const` instead of `let`: `const foo`
| ----------- help: consider using `const` instead of `let`: `const foo`
...
LL | asm!("{}", clobber_abi("C"), const foo);
| ^^^ non-constant value
@ -412,7 +412,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:57:31
|
LL | let mut foo = 0;
| ---------- help: consider using `const` instead of `let`: `const foo`
| ----------- help: consider using `const` instead of `let`: `const foo`
...
LL | asm!("{a}", a = const foo, a = const bar);
| ^^^ non-constant value
@ -421,7 +421,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:57:46
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{a}", a = const foo, a = const bar);
| ^^^ non-constant value
@ -430,7 +430,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:64:46
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{a}", in("eax") foo, a = const bar);
| ^^^ non-constant value
@ -439,7 +439,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:67:46
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{a}", in("eax") foo, a = const bar);
| ^^^ non-constant value
@ -448,7 +448,7 @@ error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/parse-error.rs:70:42
|
LL | let mut bar = 0;
| ---------- help: consider using `const` instead of `let`: `const bar`
| ----------- help: consider using `const` instead of `let`: `const bar`
...
LL | asm!("{1}", in("eax") foo, const bar);
| ^^^ non-constant value

21
src/test/ui/consts/issue-91560.fixed Normal file
View file

@ -0,0 +1,21 @@
// Regression test for issue #91560.
// run-rustfix
#![allow(unused,non_upper_case_globals)]
fn foo() {
const length: usize = 2;
//~^ HELP: consider using `const`
let arr = [0; length];
//~^ ERROR: attempt to use a non-constant value in a constant [E0435]
}
fn bar() {
const length: usize = 2;
//~^ HELP: consider using `const`
let arr = [0; length];
//~^ ERROR: attempt to use a non-constant value in a constant [E0435]
}
fn main() {}

21
src/test/ui/consts/issue-91560.rs Normal file
View file

@ -0,0 +1,21 @@
// Regression test for issue #91560.
// run-rustfix
#![allow(unused,non_upper_case_globals)]
fn foo() {
let mut length: usize = 2;
//~^ HELP: consider using `const`
let arr = [0; length];
//~^ ERROR: attempt to use a non-constant value in a constant [E0435]
}
fn bar() {
let length: usize = 2;
//~^ HELP: consider using `const`
let arr = [0; length];
//~^ ERROR: attempt to use a non-constant value in a constant [E0435]
}
fn main() {}

21
src/test/ui/consts/issue-91560.stderr Normal file
View file

@ -0,0 +1,21 @@
error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/issue-91560.rs:10:19
|
LL | let mut length: usize = 2;
| -------------- help: consider using `const` instead of `let`: `const length`
LL |
LL | let arr = [0; length];
| ^^^^^^ non-constant value
error[E0435]: attempt to use a non-constant value in a constant
--> $DIR/issue-91560.rs:17:19
|
LL | let length: usize = 2;
| ------------ help: consider using `const` instead of `let`: `const length`
LL |
LL | let arr = [0; length];
| ^^^^^^ non-constant value
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0435`.