Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/ide-diagnostics/src/handlers/mutability_errors.rs')
| -rw-r--r-- | crates/ide-diagnostics/src/handlers/mutability_errors.rs | 625 |
1 files changed, 625 insertions, 0 deletions
diff --git a/crates/ide-diagnostics/src/handlers/mutability_errors.rs b/crates/ide-diagnostics/src/handlers/mutability_errors.rs new file mode 100644 index 0000000000..84189a5d56 --- /dev/null +++ b/crates/ide-diagnostics/src/handlers/mutability_errors.rs @@ -0,0 +1,625 @@ +use ide_db::source_change::SourceChange; +use syntax::{AstNode, SyntaxKind, SyntaxNode, SyntaxToken, T}; +use text_edit::TextEdit; + +use crate::{fix, Diagnostic, DiagnosticsContext, Severity}; + +// Diagnostic: need-mut +// +// This diagnostic is triggered on mutating an immutable variable. +pub(crate) fn need_mut(ctx: &DiagnosticsContext<'_>, d: &hir::NeedMut) -> Diagnostic { + let fixes = (|| { + if d.local.is_ref(ctx.sema.db) { + // There is no simple way to add `mut` to `ref x` and `ref mut x` + return None; + } + let file_id = d.span.file_id.file_id()?; + let mut edit_builder = TextEdit::builder(); + let use_range = d.span.value.text_range(); + for source in d.local.sources(ctx.sema.db) { + let Some(ast) = source.name() else { continue }; + edit_builder.insert(ast.syntax().text_range().start(), "mut ".to_string()); + } + let edit = edit_builder.finish(); + Some(vec![fix( + "add_mut", + "Change it to be mutable", + SourceChange::from_text_edit(file_id, edit), + use_range, + )]) + })(); + Diagnostic::new( + "need-mut", + format!("cannot mutate immutable variable `{}`", d.local.name(ctx.sema.db)), + ctx.sema.diagnostics_display_range(d.span.clone()).range, + ) + .with_fixes(fixes) +} + +// Diagnostic: unused-mut +// +// This diagnostic is triggered when a mutable variable isn't actually mutated. +pub(crate) fn unused_mut(ctx: &DiagnosticsContext<'_>, d: &hir::UnusedMut) -> Diagnostic { + let ast = d.local.primary_source(ctx.sema.db).syntax_ptr(); + let fixes = (|| { + let file_id = ast.file_id.file_id()?; + let mut edit_builder = TextEdit::builder(); + let use_range = ast.value.text_range(); + for source in d.local.sources(ctx.sema.db) { + let ast = source.syntax(); + let Some(mut_token) = token(ast, T![mut]) else { continue }; + edit_builder.delete(mut_token.text_range()); + if let Some(token) = mut_token.next_token() { + if token.kind() == SyntaxKind::WHITESPACE { + edit_builder.delete(token.text_range()); + } + } + } + let edit = edit_builder.finish(); + Some(vec![fix( + "remove_mut", + "Remove unnecessary `mut`", + SourceChange::from_text_edit(file_id, edit), + use_range, + )]) + })(); + let ast = d.local.primary_source(ctx.sema.db).syntax_ptr(); + Diagnostic::new( + "unused-mut", + "variable does not need to be mutable", + ctx.sema.diagnostics_display_range(ast).range, + ) + .severity(Severity::WeakWarning) + .experimental() // Not supporting `#[allow(unused_mut)]` leads to false positive. + .with_fixes(fixes) +} + +pub(super) fn token(parent: &SyntaxNode, kind: SyntaxKind) -> Option<SyntaxToken> { + parent.children_with_tokens().filter_map(|it| it.into_token()).find(|it| it.kind() == kind) +} + +#[cfg(test)] +mod tests { + use crate::tests::{check_diagnostics, check_fix}; + + #[test] + fn unused_mut_simple() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x = 2; + //^^^^^ 💡 weak: variable does not need to be mutable + f(x); +} +"#, + ); + } + + #[test] + fn no_false_positive_simple() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let x = 2; + f(x); +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x = 2; + x = 5; + f(x); +} +"#, + ); + } + + #[test] + fn multiple_errors_for_single_variable() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let x = 2; + x = 10; + //^^^^^^ 💡 error: cannot mutate immutable variable `x` + x = 5; + //^^^^^ 💡 error: cannot mutate immutable variable `x` + &mut x; + //^^^^^^ 💡 error: cannot mutate immutable variable `x` + f(x); +} +"#, + ); + } + + #[test] + fn unused_mut_fix() { + check_fix( + r#" +fn f(_: i32) {} +fn main() { + let mu$0t x = 2; + f(x); +} +"#, + r#" +fn f(_: i32) {} +fn main() { + let x = 2; + f(x); +} +"#, + ); + check_fix( + r#" +fn f(_: i32) {} +fn main() { + let ((mu$0t x, _) | (_, mut x)) = (2, 3); + f(x); +} +"#, + r#" +fn f(_: i32) {} +fn main() { + let ((x, _) | (_, x)) = (2, 3); + f(x); +} +"#, + ); + } + + #[test] + fn need_mut_fix() { + check_fix( + r#" +fn f(_: i32) {} +fn main() { + let x = 2; + x$0 = 5; + f(x); +} +"#, + r#" +fn f(_: i32) {} +fn main() { + let mut x = 2; + x = 5; + f(x); +} +"#, + ); + check_fix( + r#" +fn f(_: i32) {} +fn main() { + let ((x, _) | (_, x)) = (2, 3); + x =$0 4; + f(x); +} +"#, + r#" +fn f(_: i32) {} +fn main() { + let ((mut x, _) | (_, mut x)) = (2, 3); + x = 4; + f(x); +} +"#, + ); + + check_fix( + r#" +struct Foo(i32); + +impl Foo { + fn foo(self) { + self = Fo$0o(5); + } +} +"#, + r#" +struct Foo(i32); + +impl Foo { + fn foo(mut self) { + self = Foo(5); + } +} +"#, + ); + } + + #[test] + fn need_mut_fix_not_applicable_on_ref() { + check_diagnostics( + r#" +fn main() { + let ref x = 2; + x = &5; + //^^^^^^ error: cannot mutate immutable variable `x` +} +"#, + ); + check_diagnostics( + r#" +fn main() { + let ref mut x = 2; + x = &mut 5; + //^^^^^^^^^^ error: cannot mutate immutable variable `x` +} +"#, + ); + } + + #[test] + fn field_mutate() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x = (2, 7); + //^^^^^ 💡 weak: variable does not need to be mutable + f(x.1); +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x = (2, 7); + x.0 = 5; + f(x.1); +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let x = (2, 7); + x.0 = 5; + //^^^^^^^ 💡 error: cannot mutate immutable variable `x` + f(x.1); +} +"#, + ); + } + + #[test] + fn mutable_reference() { + check_diagnostics( + r#" +fn main() { + let mut x = &mut 2; + //^^^^^ 💡 weak: variable does not need to be mutable + *x = 5; +} +"#, + ); + check_diagnostics( + r#" +fn main() { + let x = 2; + &mut x; + //^^^^^^ 💡 error: cannot mutate immutable variable `x` +} +"#, + ); + check_diagnostics( + r#" +fn main() { + let x_own = 2; + let ref mut x_ref = x_own; + //^^^^^^^^^^^^^ 💡 error: cannot mutate immutable variable `x_own` +} +"#, + ); + check_diagnostics( + r#" +struct Foo; +impl Foo { + fn method(&mut self, x: i32) {} +} +fn main() { + let x = Foo; + x.method(2); + //^ 💡 error: cannot mutate immutable variable `x` +} +"#, + ); + } + + #[test] + fn regression_14310() { + check_diagnostics( + r#" + fn clone(mut i: &!) -> ! { + //^^^^^ 💡 weak: variable does not need to be mutable + *i + } + "#, + ); + } + + #[test] + fn match_bindings() { + check_diagnostics( + r#" +fn main() { + match (2, 3) { + (x, mut y) => { + //^^^^^ 💡 weak: variable does not need to be mutable + x = 7; + //^^^^^ 💡 error: cannot mutate immutable variable `x` + } + } +} +"#, + ); + } + + #[test] + fn mutation_in_dead_code() { + // This one is interesting. Dead code is not represented at all in the MIR, so + // there would be no mutablility error for locals in dead code. Rustc tries to + // not emit `unused_mut` in this case, but since it works without `mut`, and + // special casing it is not trivial, we emit it. + check_diagnostics( + r#" +fn main() { + return; + let mut x = 2; + //^^^^^ 💡 weak: variable does not need to be mutable + &mut x; +} +"#, + ); + check_diagnostics( + r#" +fn main() { + loop {} + let mut x = 2; + //^^^^^ 💡 weak: variable does not need to be mutable + &mut x; +} +"#, + ); + check_diagnostics( + r#" +enum X {} +fn g() -> X { + loop {} +} +fn f() -> ! { + loop {} +} +fn main(b: bool) { + if b { + f(); + } else { + g(); + } + let mut x = 2; + //^^^^^ 💡 weak: variable does not need to be mutable + &mut x; +} +"#, + ); + check_diagnostics( + r#" +fn main(b: bool) { + if b { + loop {} + } else { + return; + } + let mut x = 2; + //^^^^^ 💡 weak: variable does not need to be mutable + &mut x; +} +"#, + ); + } + + #[test] + fn initialization_is_not_mutation() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x; + //^^^^^ 💡 weak: variable does not need to be mutable + x = 5; + f(x); +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main(b: bool) { + let mut x; + //^^^^^ 💡 weak: variable does not need to be mutable + if b { + x = 1; + } else { + x = 3; + } + f(x); +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main(b: bool) { + let x; + if b { + x = 1; + } + x = 3; + //^^^^^ 💡 error: cannot mutate immutable variable `x` + f(x); +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let x; + loop { + x = 1; + //^^^^^ 💡 error: cannot mutate immutable variable `x` + f(x); + } +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + loop { + let mut x = 1; + //^^^^^ 💡 weak: variable does not need to be mutable + f(x); + if let mut y = 2 { + //^^^^^ 💡 weak: variable does not need to be mutable + f(y); + } + match 3 { + mut z => f(z), + //^^^^^ 💡 weak: variable does not need to be mutable + } + } +} +"#, + ); + } + + #[test] + fn function_arguments_are_initialized() { + check_diagnostics( + r#" +fn f(mut x: i32) { + //^^^^^ 💡 weak: variable does not need to be mutable +} +"#, + ); + check_diagnostics( + r#" +fn f(x: i32) { + x = 5; + //^^^^^ 💡 error: cannot mutate immutable variable `x` +} +"#, + ); + } + + #[test] + fn for_loop() { + check_diagnostics( + r#" +//- minicore: iterators +fn f(x: [(i32, u8); 10]) { + for (a, mut b) in x { + //^^^^^ 💡 weak: variable does not need to be mutable + a = 2; + //^^^^^ 💡 error: cannot mutate immutable variable `a` + } +} +"#, + ); + } + + #[test] + fn overloaded_deref() { + // FIXME: check for false negative + check_diagnostics( + r#" +//- minicore: deref_mut +use core::ops::{Deref, DerefMut}; + +struct Foo; +impl Deref for Foo { + type Target = i32; + fn deref(&self) -> &i32 { + &5 + } +} +impl DerefMut for Foo { + fn deref_mut(&mut self) -> &mut i32 { + &mut 5 + } +} +fn f() { + let x = Foo; + let y = &*x; + let x = Foo; + let mut x = Foo; + let y: &mut i32 = &mut x; +} +"#, + ); + } + + #[test] + fn or_pattern() { + check_diagnostics( + r#" +//- minicore: option +fn f(_: i32) {} +fn main() { + let ((Some(mut x), None) | (_, Some(mut x))) = (None, Some(7)); + //^^^^^ 💡 weak: variable does not need to be mutable + f(x); +} +"#, + ); + } + + #[test] + fn or_pattern_no_terminator() { + check_diagnostics( + r#" +enum Foo { + A, B, C, D +} + +use Foo::*; + +fn f(inp: (Foo, Foo, Foo, Foo)) { + let ((A, B, _, x) | (B, C | D, x, _)) = inp else { + return; + }; + x = B; + //^^^^^ 💡 error: cannot mutate immutable variable `x` +} +"#, + ); + } + + #[test] + fn respect_allow_unused_mut() { + // FIXME: respect + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + #[allow(unused_mut)] + let mut x = 2; + //^^^^^ 💡 weak: variable does not need to be mutable + f(x); +} +"#, + ); + } +} |