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Tighten the 'introduce new binding' suggestion #104186

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Nov 10, 2022
Merged

Tighten the 'introduce new binding' suggestion #104186

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952df48
Fix #104086, Tighten the 'introduce new binding' suggestion
chenyukang Nov 9, 2022
5689f9c
fix tests and code cleanup
chenyukang Nov 9, 2022
c69872b
add 'is_assign_rhs' to avoid weird suggesting 'let'
chenyukang Nov 9, 2022
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14 changes: 10 additions & 4 deletions compiler/rustc_resolve/src/late.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -527,6 +527,7 @@ struct DiagnosticMetadata<'ast> {

/// Used to detect possible new binding written without `let` and to provide structured suggestion.
in_assignment: Option<&'ast Expr>,
is_assign_rhs: bool,

/// If we are currently in a trait object definition. Used to point at the bounds when
/// encountering a struct or enum.
Expand Down Expand Up @@ -3963,10 +3964,15 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
self.resolve_expr(elem, Some(expr));
self.visit_expr(idx);
}
ExprKind::Assign(..) => {
let old = self.diagnostic_metadata.in_assignment.replace(expr);
visit::walk_expr(self, expr);
self.diagnostic_metadata.in_assignment = old;
ExprKind::Assign(ref lhs, ref rhs, _) => {
if !self.diagnostic_metadata.is_assign_rhs {
self.diagnostic_metadata.in_assignment = Some(expr);
}
self.visit_expr(lhs);
self.diagnostic_metadata.is_assign_rhs = true;
self.diagnostic_metadata.in_assignment = None;
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Should we reinstate the overwritten value, instead of putting None in all cases?

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we only care about the lhs of assignment.

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And the backup state is not important, the check logic is invoked by visit_expr.

self.visit_expr(rhs);
self.diagnostic_metadata.is_assign_rhs = false;
}
_ => {
visit::walk_expr(self, expr);
Expand Down
21 changes: 7 additions & 14 deletions compiler/rustc_resolve/src/late/diagnostics.rs
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Expand Up @@ -1810,29 +1810,22 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
false
}

fn let_binding_suggestion(&self, err: &mut Diagnostic, ident_span: Span) -> bool {
// try to give a suggestion for this pattern: `name = 1`, which is common in other languages
let mut added_suggestion = false;
if let Some(Expr { kind: ExprKind::Assign(lhs, _rhs, _), .. }) = self.diagnostic_metadata.in_assignment &&
// try to give a suggestion for this pattern: `name = blah`, which is common in other languages
// suggest `let name = blah` to introduce a new binding
fn let_binding_suggestion(&mut self, err: &mut Diagnostic, ident_span: Span) -> bool {
if let Some(Expr { kind: ExprKind::Assign(lhs, .. ), .. }) = self.diagnostic_metadata.in_assignment &&
let ast::ExprKind::Path(None, _) = lhs.kind {
let sm = self.r.session.source_map();
let line_span = sm.span_extend_to_line(ident_span);
let ident_name = sm.span_to_snippet(ident_span).unwrap();
// HACK(chenyukang): make sure ident_name is at the starting of the line to protect against macros
if sm
.span_to_snippet(line_span)
.map_or(false, |s| s.trim().starts_with(&ident_name))
{
if !ident_span.from_expansion() {
err.span_suggestion_verbose(
ident_span.shrink_to_lo(),
"you might have meant to introduce a new binding",
"let ".to_string(),
Applicability::MaybeIncorrect,
);
added_suggestion = true;
return true;
}
}
added_suggestion
false
}

fn find_module(&mut self, def_id: DefId) -> Option<(Module<'a>, ImportSuggestion)> {
Expand Down
30 changes: 30 additions & 0 deletions src/test/ui/suggestions/issue-104086-suggest-let.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
fn main() {
x = x = x;
//~^ ERROR cannot find value `x` in this scope
//~| ERROR cannot find value `x` in this scope
//~| ERROR cannot find value `x` in this scope

x = y = y = y;
//~^ ERROR cannot find value `y` in this scope
//~| ERROR cannot find value `y` in this scope
//~| ERROR cannot find value `y` in this scope
//~| ERROR cannot find value `x` in this scope

x = y = y;
//~^ ERROR cannot find value `x` in this scope
//~| ERROR cannot find value `y` in this scope
//~| ERROR cannot find value `y` in this scope

x = x = y;
//~^ ERROR cannot find value `x` in this scope
//~| ERROR cannot find value `x` in this scope
//~| ERROR cannot find value `y` in this scope

x = x; // will suggest add `let`
//~^ ERROR cannot find value `x` in this scope
//~| ERROR cannot find value `x` in this scope

x = y // will suggest add `let`
//~^ ERROR cannot find value `x` in this scope
//~| ERROR cannot find value `y` in this scope
}
135 changes: 135 additions & 0 deletions src/test/ui/suggestions/issue-104086-suggest-let.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,135 @@
error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:2:5
|
LL | x = x = x;
| ^
|
help: you might have meant to introduce a new binding
|
LL | let x = x = x;
| +++

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:2:9
|
LL | x = x = x;
| ^ not found in this scope

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:2:13
|
LL | x = x = x;
| ^ not found in this scope

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:7:5
|
LL | x = y = y = y;
| ^
|
help: you might have meant to introduce a new binding
|
LL | let x = y = y = y;
| +++

error[E0425]: cannot find value `y` in this scope
--> $DIR/issue-104086-suggest-let.rs:7:9
|
LL | x = y = y = y;
| ^ not found in this scope

error[E0425]: cannot find value `y` in this scope
--> $DIR/issue-104086-suggest-let.rs:7:13
|
LL | x = y = y = y;
| ^ not found in this scope

error[E0425]: cannot find value `y` in this scope
--> $DIR/issue-104086-suggest-let.rs:7:17
|
LL | x = y = y = y;
| ^ not found in this scope

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:13:5
|
LL | x = y = y;
| ^
|
help: you might have meant to introduce a new binding
|
LL | let x = y = y;
| +++

error[E0425]: cannot find value `y` in this scope
--> $DIR/issue-104086-suggest-let.rs:13:9
|
LL | x = y = y;
| ^ not found in this scope

error[E0425]: cannot find value `y` in this scope
--> $DIR/issue-104086-suggest-let.rs:13:13
|
LL | x = y = y;
| ^ not found in this scope

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:18:5
|
LL | x = x = y;
| ^
|
help: you might have meant to introduce a new binding
|
LL | let x = x = y;
| +++

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:18:9
|
LL | x = x = y;
| ^ not found in this scope

error[E0425]: cannot find value `y` in this scope
--> $DIR/issue-104086-suggest-let.rs:18:13
|
LL | x = x = y;
| ^ not found in this scope

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:23:5
|
LL | x = x; // will suggest add `let`
| ^
|
help: you might have meant to introduce a new binding
|
LL | let x = x; // will suggest add `let`
| +++

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:23:9
|
LL | x = x; // will suggest add `let`
| ^ not found in this scope

error[E0425]: cannot find value `x` in this scope
--> $DIR/issue-104086-suggest-let.rs:27:5
|
LL | x = y // will suggest add `let`
| ^
|
help: you might have meant to introduce a new binding
|
LL | let x = y // will suggest add `let`
| +++

error[E0425]: cannot find value `y` in this scope
--> $DIR/issue-104086-suggest-let.rs:27:9
|
LL | x = y // will suggest add `let`
| ^ not found in this scope

error: aborting due to 17 previous errors

For more information about this error, try `rustc --explain E0425`.