rust/src/librustc/lint/builtin.rs

//! Some lints that are built in to the compiler.
//!
//! These are the built-in lints that are emitted direct in the main
//! compiler code, rather than using their own custom pass. Those
//! lints are all available in `rustc_lint::builtin`.

use crate::lint::{LintPass, LateLintPass, LintArray};
use crate::session::Session;
use errors::{Applicability, DiagnosticBuilder};
use syntax::ast;
use syntax::source_map::Span;

declare_lint! {
    pub EXCEEDING_BITSHIFTS,
    Deny,
    "shift exceeds the type's number of bits"
}

declare_lint! {
    pub CONST_ERR,
    Deny,
    "constant evaluation detected erroneous expression"
}

declare_lint! {
    pub UNUSED_IMPORTS,
    Warn,
    "imports that are never used"
}

declare_lint! {
    pub UNUSED_EXTERN_CRATES,
    Allow,
    "extern crates that are never used"
}

declare_lint! {
    pub UNUSED_QUALIFICATIONS,
    Allow,
    "detects unnecessarily qualified names"
}

declare_lint! {
    pub UNKNOWN_LINTS,
    Warn,
    "unrecognized lint attribute"
}

declare_lint! {
    pub UNUSED_VARIABLES,
    Warn,
    "detect variables which are not used in any way"
}

declare_lint! {
    pub UNUSED_ASSIGNMENTS,
    Warn,
    "detect assignments that will never be read"
}

declare_lint! {
    pub DEAD_CODE,
    Warn,
    "detect unused, unexported items"
}

declare_lint! {
    pub UNREACHABLE_CODE,
    Warn,
    "detects unreachable code paths",
    report_in_external_macro: true
}

declare_lint! {
    pub UNREACHABLE_PATTERNS,
    Warn,
    "detects unreachable patterns"
}

declare_lint! {
    pub UNUSED_MACROS,
    Warn,
    "detects macros that were not used"
}

declare_lint! {
    pub WARNINGS,
    Warn,
    "mass-change the level for lints which produce warnings"
}

declare_lint! {
    pub UNUSED_FEATURES,
    Warn,
    "unused features found in crate-level #[feature] directives"
}

declare_lint! {
    pub STABLE_FEATURES,
    Warn,
    "stable features found in #[feature] directive"
}

declare_lint! {
    pub UNKNOWN_CRATE_TYPES,
    Deny,
    "unknown crate type found in #[crate_type] directive"
}

declare_lint! {
    pub TRIVIAL_CASTS,
    Allow,
    "detects trivial casts which could be removed"
}

declare_lint! {
    pub TRIVIAL_NUMERIC_CASTS,
    Allow,
    "detects trivial casts of numeric types which could be removed"
}

declare_lint! {
    pub PRIVATE_IN_PUBLIC,
    Warn,
    "detect private items in public interfaces not caught by the old implementation"
}

declare_lint! {
    pub EXPORTED_PRIVATE_DEPENDENCIES,
    Warn,
    "public interface leaks type from a private dependency"
}

declare_lint! {
    pub PUB_USE_OF_PRIVATE_EXTERN_CRATE,
    Deny,
    "detect public re-exports of private extern crates"
}

declare_lint! {
    pub INVALID_TYPE_PARAM_DEFAULT,
    Deny,
    "type parameter default erroneously allowed in invalid location"
}

declare_lint! {
    pub RENAMED_AND_REMOVED_LINTS,
    Warn,
    "lints that have been renamed or removed"
}

declare_lint! {
    pub SAFE_EXTERN_STATICS,
    Deny,
    "safe access to extern statics was erroneously allowed"
}

declare_lint! {
    pub SAFE_PACKED_BORROWS,
    Warn,
    "safe borrows of fields of packed structs were was erroneously allowed"
}

declare_lint! {
    pub PATTERNS_IN_FNS_WITHOUT_BODY,
    Warn,
    "patterns in functions without body were erroneously allowed"
}

declare_lint! {
    pub LEGACY_DIRECTORY_OWNERSHIP,
    Deny,
    "non-inline, non-`#[path]` modules (e.g., `mod foo;`) were erroneously allowed in some files \
     not named `mod.rs`"
}

declare_lint! {
    pub LEGACY_CONSTRUCTOR_VISIBILITY,
    Deny,
    "detects use of struct constructors that would be invisible with new visibility rules"
}

declare_lint! {
    pub MISSING_FRAGMENT_SPECIFIER,
    Deny,
    "detects missing fragment specifiers in unused `macro_rules!` patterns"
}

declare_lint! {
    pub PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
    Deny,
    "detects parenthesized generic parameters in type and module names"
}

declare_lint! {
    pub LATE_BOUND_LIFETIME_ARGUMENTS,
    Warn,
    "detects generic lifetime arguments in path segments with late bound lifetime parameters"
}

declare_lint! {
    pub INCOHERENT_FUNDAMENTAL_IMPLS,
    Deny,
    "potentially-conflicting impls were erroneously allowed"
}

declare_lint! {
    pub ORDER_DEPENDENT_TRAIT_OBJECTS,
    Deny,
    "trait-object types were treated as different depending on marker-trait order"
}

declare_lint! {
    pub DEPRECATED,
    Warn,
    "detects use of deprecated items",
    report_in_external_macro: true
}

declare_lint! {
    pub UNUSED_UNSAFE,
    Warn,
    "unnecessary use of an `unsafe` block"
}

declare_lint! {
    pub UNUSED_MUT,
    Warn,
    "detect mut variables which don't need to be mutable"
}

declare_lint! {
    pub UNCONDITIONAL_RECURSION,
    Warn,
    "functions that cannot return without calling themselves"
}

declare_lint! {
    pub SINGLE_USE_LIFETIMES,
    Allow,
    "detects lifetime parameters that are only used once"
}

declare_lint! {
    pub UNUSED_LIFETIMES,
    Allow,
    "detects lifetime parameters that are never used"
}

declare_lint! {
    pub TYVAR_BEHIND_RAW_POINTER,
    Warn,
    "raw pointer to an inference variable"
}

declare_lint! {
    pub ELIDED_LIFETIMES_IN_PATHS,
    Allow,
    "hidden lifetime parameters in types are deprecated"
}

declare_lint! {
    pub BARE_TRAIT_OBJECTS,
    Allow,
    "suggest using `dyn Trait` for trait objects"
}

declare_lint! {
    pub ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
    Allow,
    "fully qualified paths that start with a module name \
     instead of `crate`, `self`, or an extern crate name"
}

declare_lint! {
    pub ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
    Warn,
    "floating-point literals cannot be used in patterns"
}

declare_lint! {
    pub UNSTABLE_NAME_COLLISIONS,
    Warn,
    "detects name collision with an existing but unstable method"
}

declare_lint! {
    pub IRREFUTABLE_LET_PATTERNS,
    Warn,
    "detects irrefutable patterns in if-let and while-let statements"
}

declare_lint! {
    pub UNUSED_LABELS,
    Allow,
    "detects labels that are never used"
}

declare_lint! {
    pub DUPLICATE_MACRO_EXPORTS,
    Deny,
    "detects duplicate macro exports"
}

declare_lint! {
    pub INTRA_DOC_LINK_RESOLUTION_FAILURE,
    Warn,
    "failures in resolving intra-doc link targets"
}

declare_lint! {
    pub MISSING_DOC_CODE_EXAMPLES,
    Allow,
    "detects publicly-exported items without code samples in their documentation"
}

declare_lint! {
    pub PRIVATE_DOC_TESTS,
    Allow,
    "detects code samples in docs of private items not documented by rustdoc"
}

declare_lint! {
    pub WHERE_CLAUSES_OBJECT_SAFETY,
    Warn,
    "checks the object safety of where clauses"
}

declare_lint! {
    pub PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
    Warn,
    "detects proc macro derives using inaccessible names from parent modules"
}

declare_lint! {
    pub MACRO_USE_EXTERN_CRATE,
    Allow,
    "the `#[macro_use]` attribute is now deprecated in favor of using macros \
     via the module system"
}

declare_lint! {
    pub MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
    Deny,
    "macro-expanded `macro_export` macros from the current crate \
     cannot be referred to by absolute paths"
}

declare_lint! {
    pub EXPLICIT_OUTLIVES_REQUIREMENTS,
    Allow,
    "outlives requirements can be inferred"
}

declare_lint! {
    pub DUPLICATE_MATCHER_BINDING_NAME,
    Deny,
    "duplicate macro matcher binding name"
}

/// Some lints that are buffered from `libsyntax`. See `syntax::early_buffered_lints`.
pub mod parser {
    declare_lint! {
        pub QUESTION_MARK_MACRO_SEP,
        Allow,
        "detects the use of `?` as a macro separator"
    }

    declare_lint! {
        pub ILL_FORMED_ATTRIBUTE_INPUT,
        Warn,
        "ill-formed attribute inputs that were previously accepted and used in practice"
    }
}

declare_lint! {
    pub DEPRECATED_IN_FUTURE,
    Allow,
    "detects use of items that will be deprecated in a future version",
    report_in_external_macro: true
}

declare_lint! {
    pub AMBIGUOUS_ASSOCIATED_ITEMS,
    Warn,
    "ambiguous associated items"
}

declare_lint! {
    pub NESTED_IMPL_TRAIT,
    Warn,
    "nested occurrence of `impl Trait` type"
}

declare_lint! {
    pub MUTABLE_BORROW_RESERVATION_CONFLICT,
    Warn,
    "reservation of a two-phased borrow conflicts with other shared borrows"
}

declare_lint_pass! {
    /// Does nothing as a lint pass, but registers some `Lint`s
    /// that are used by other parts of the compiler.
    HardwiredLints => [
        ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
        EXCEEDING_BITSHIFTS,
        UNUSED_IMPORTS,
        UNUSED_EXTERN_CRATES,
        UNUSED_QUALIFICATIONS,
        UNKNOWN_LINTS,
        UNUSED_VARIABLES,
        UNUSED_ASSIGNMENTS,
        DEAD_CODE,
        UNREACHABLE_CODE,
        UNREACHABLE_PATTERNS,
        UNUSED_MACROS,
        WARNINGS,
        UNUSED_FEATURES,
        STABLE_FEATURES,
        UNKNOWN_CRATE_TYPES,
        TRIVIAL_CASTS,
        TRIVIAL_NUMERIC_CASTS,
        PRIVATE_IN_PUBLIC,
        EXPORTED_PRIVATE_DEPENDENCIES,
        PUB_USE_OF_PRIVATE_EXTERN_CRATE,
        INVALID_TYPE_PARAM_DEFAULT,
        CONST_ERR,
        RENAMED_AND_REMOVED_LINTS,
        SAFE_EXTERN_STATICS,
        SAFE_PACKED_BORROWS,
        PATTERNS_IN_FNS_WITHOUT_BODY,
        LEGACY_DIRECTORY_OWNERSHIP,
        LEGACY_CONSTRUCTOR_VISIBILITY,
        MISSING_FRAGMENT_SPECIFIER,
        PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
        LATE_BOUND_LIFETIME_ARGUMENTS,
        INCOHERENT_FUNDAMENTAL_IMPLS,
        ORDER_DEPENDENT_TRAIT_OBJECTS,
        DEPRECATED,
        UNUSED_UNSAFE,
        UNUSED_MUT,
        UNCONDITIONAL_RECURSION,
        SINGLE_USE_LIFETIMES,
        UNUSED_LIFETIMES,
        UNUSED_LABELS,
        TYVAR_BEHIND_RAW_POINTER,
        ELIDED_LIFETIMES_IN_PATHS,
        BARE_TRAIT_OBJECTS,
        ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
        UNSTABLE_NAME_COLLISIONS,
        IRREFUTABLE_LET_PATTERNS,
        DUPLICATE_MACRO_EXPORTS,
        INTRA_DOC_LINK_RESOLUTION_FAILURE,
        MISSING_DOC_CODE_EXAMPLES,
        PRIVATE_DOC_TESTS,
        WHERE_CLAUSES_OBJECT_SAFETY,
        PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
        MACRO_USE_EXTERN_CRATE,
        MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
        parser::QUESTION_MARK_MACRO_SEP,
        parser::ILL_FORMED_ATTRIBUTE_INPUT,
        DEPRECATED_IN_FUTURE,
        AMBIGUOUS_ASSOCIATED_ITEMS,
        NESTED_IMPL_TRAIT,
        DUPLICATE_MATCHER_BINDING_NAME,
        MUTABLE_BORROW_RESERVATION_CONFLICT,
    ]
}

// this could be a closure, but then implementing derive traits
// becomes hacky (and it gets allocated)
#[derive(PartialEq, RustcEncodable, RustcDecodable, Debug)]
pub enum BuiltinLintDiagnostics {
    Normal,
    BareTraitObject(Span, /* is_global */ bool),
    AbsPathWithModule(Span),
    DuplicatedMacroExports(ast::Ident, Span, Span),
    ProcMacroDeriveResolutionFallback(Span),
    MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
    ElidedLifetimesInPaths(usize, Span, bool, Span, String),
    UnknownCrateTypes(Span, String, String),
    UnusedImports(String, Vec<(Span, String)>),
    NestedImplTrait { outer_impl_trait_span: Span, inner_impl_trait_span: Span },
    RedundantImport(Vec<(Span, bool)>, ast::Ident),
}

impl BuiltinLintDiagnostics {
    pub fn run(self, sess: &Session, db: &mut DiagnosticBuilder<'_>) {
        match self {
            BuiltinLintDiagnostics::Normal => (),
            BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
                let (sugg, app) = match sess.source_map().span_to_snippet(span) {
                    Ok(ref s) if is_global => (format!("dyn ({})", s),
                                               Applicability::MachineApplicable),
                    Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
                    Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders)
                };
                db.span_suggestion(span, "use `dyn`", sugg, app);
            }
            BuiltinLintDiagnostics::AbsPathWithModule(span) => {
                let (sugg, app) = match sess.source_map().span_to_snippet(span) {
                    Ok(ref s) => {
                        // FIXME(Manishearth) ideally the emitting code
                        // can tell us whether or not this is global
                        let opt_colon = if s.trim_start().starts_with("::") {
                            ""
                        } else {
                            "::"
                        };

                        (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
                    }
                    Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders)
                };
                db.span_suggestion(span, "use `crate`", sugg, app);
            }
            BuiltinLintDiagnostics::DuplicatedMacroExports(ident, earlier_span, later_span) => {
                db.span_label(later_span, format!("`{}` already exported", ident));
                db.span_note(earlier_span, "previous macro export is now shadowed");
            }
            BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
                db.span_label(span, "names from parent modules are not \
                                     accessible without an explicit import");
            }
            BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(span_def) => {
                db.span_note(span_def, "the macro is defined here");
            }
            BuiltinLintDiagnostics::ElidedLifetimesInPaths(
                n, path_span, incl_angl_brckt, insertion_span, anon_lts
            ) => {
                let (replace_span, suggestion) = if incl_angl_brckt {
                    (insertion_span, anon_lts)
                } else {
                    // When possible, prefer a suggestion that replaces the whole
                    // `Path<T>` expression with `Path<'_, T>`, rather than inserting `'_, `
                    // at a point (which makes for an ugly/confusing label)
                    if let Ok(snippet) = sess.source_map().span_to_snippet(path_span) {
                        // But our spans can get out of whack due to macros; if the place we think
                        // we want to insert `'_` isn't even within the path expression's span, we
                        // should bail out of making any suggestion rather than panicking on a
                        // subtract-with-overflow or string-slice-out-out-bounds (!)
                        // FIXME: can we do better?
                        if insertion_span.lo().0 < path_span.lo().0 {
                            return;
                        }
                        let insertion_index = (insertion_span.lo().0 - path_span.lo().0) as usize;
                        if insertion_index > snippet.len() {
                            return;
                        }
                        let (before, after) = snippet.split_at(insertion_index);
                        (path_span, format!("{}{}{}", before, anon_lts, after))
                    } else {
                        (insertion_span, anon_lts)
                    }
                };
                db.span_suggestion(
                    replace_span,
                    &format!("indicate the anonymous lifetime{}", if n >= 2 { "s" } else { "" }),
                    suggestion,
                    Applicability::MachineApplicable
                );
            }
            BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
                db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
            }
            BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
                if !replaces.is_empty() {
                    db.tool_only_multipart_suggestion(
                        &message,
                        replaces,
                        Applicability::MachineApplicable,
                    );
                }
            }
            BuiltinLintDiagnostics::NestedImplTrait {
                outer_impl_trait_span, inner_impl_trait_span
            } => {
                db.span_label(outer_impl_trait_span, "outer `impl Trait`");
                db.span_label(inner_impl_trait_span, "nested `impl Trait` here");
            }
            BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
                for (span, is_imported) in spans {
                    let introduced = if is_imported { "imported" } else { "defined" };
                    db.span_label(
                        span,
                        format!("the item `{}` is already {} here", ident, introduced)
                    );
                }
            }
        }
    }
}

impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HardwiredLints {}