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 | 302 |
1 files changed, 302 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..a78b58fdc8 --- /dev/null +++ b/crates/ide-diagnostics/src/handlers/mutability_errors.rs @@ -0,0 +1,302 @@ +use crate::{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 { + Diagnostic::new( + "need-mut", + format!("cannot mutate immutable variable `{}`", d.local.name(ctx.sema.db)), + ctx.sema.diagnostics_display_range(d.span.clone()).range, + ) +} + +// 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 { + Diagnostic::new( + "unused-mut", + "remove this `mut`", + ctx.sema.diagnostics_display_range(d.local.primary_source(ctx.sema.db).syntax_ptr()).range, + ) + .severity(Severity::WeakWarning) +} + +#[cfg(test)] +mod tests { + use crate::tests::check_diagnostics; + + #[test] + fn unused_mut_simple() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x = 2; + //^^^^^ weak: remove this `mut` + 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 field_mutate() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x = (2, 7); + //^^^^^ weak: remove this `mut` + 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: remove this `mut` + *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 match_bindings() { + check_diagnostics( + r#" +fn main() { + match (2, 3) { + (x, mut y) => { + //^^^^^ weak: remove this `mut` + 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: remove this `mut` + &mut x; +} +"#, + ); + check_diagnostics( + r#" +fn main() { + loop {} + let mut x = 2; + //^^^^^ weak: remove this `mut` + &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: remove this `mut` + &mut x; +} +"#, + ); + check_diagnostics( + r#" +fn main(b: bool) { + if b { + loop {} + } else { + return; + } + let mut x = 2; + //^^^^^ weak: remove this `mut` + &mut x; +} +"#, + ); + } + + #[test] + fn initialization_is_not_mutation() { + check_diagnostics( + r#" +fn f(_: i32) {} +fn main() { + let mut x; + //^^^^^ weak: remove this `mut` + x = 5; + f(x); +} +"#, + ); + check_diagnostics( + r#" +fn f(_: i32) {} +fn main(b: bool) { + let mut x; + //^^^^^ weak: remove this `mut` + 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: remove this `mut` + f(x); + if let mut y = 2 { + //^^^^^ weak: remove this `mut` + f(y); + } + match 3 { + mut z => f(z), + //^^^^^ weak: remove this `mut` + } + } +} +"#, + ); + } +} |