9 files changed, 489 insertions, 72 deletions

diff --git a/crates/ra_ide/src/completion/complete_attribute.rs b/crates/ra_ide/src/completion/complete_attribute.rs
index d268c92be..109c5e9a8 100644
--- a/crates/ra_ide/src/completion/complete_attribute.rs
+++ b/crates/ra_ide/src/completion/complete_attribute.rs
@@ -13,13 +13,19 @@ use crate::completion::{
 
 pub(super) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
     let attribute = ctx.attribute_under_caret.as_ref()?;
-
     match (attribute.path(), attribute.input()) {
         (Some(path), Some(ast::AttrInput::TokenTree(token_tree)))
             if path.to_string() == "derive" =>
         {
             complete_derive(acc, ctx, token_tree)
         }
+        (Some(path), Some(ast::AttrInput::TokenTree(token_tree)))
+            if ["allow", "warn", "deny", "forbid"]
+                .iter()
+                .any(|lint_level| lint_level == &path.to_string()) =>
+        {
+            complete_lint(acc, ctx, token_tree)
+        }
         (_, Some(ast::AttrInput::TokenTree(_token_tree))) => {}
         _ => complete_attribute_start(acc, ctx, attribute),
     }
@@ -125,7 +131,7 @@ const ATTRIBUTES: &[AttrCompletion] = &[
 ];
 
 fn complete_derive(acc: &mut Completions, ctx: &CompletionContext, derive_input: ast::TokenTree) {
-    if let Ok(existing_derives) = parse_derive_input(derive_input) {
+    if let Ok(existing_derives) = parse_comma_sep_input(derive_input) {
         for derive_completion in DEFAULT_DERIVE_COMPLETIONS
             .into_iter()
             .filter(|completion| !existing_derives.contains(completion.label))
@@ -158,7 +164,26 @@ fn complete_derive(acc: &mut Completions, ctx: &CompletionContext, derive_input:
     }
 }
 
-fn parse_derive_input(derive_input: ast::TokenTree) -> Result<FxHashSet<String>, ()> {
+fn complete_lint(acc: &mut Completions, ctx: &CompletionContext, derive_input: ast::TokenTree) {
+    if let Ok(existing_lints) = parse_comma_sep_input(derive_input) {
+        for lint_completion in DEFAULT_LINT_COMPLETIONS
+            .into_iter()
+            .filter(|completion| !existing_lints.contains(completion.label))
+        {
+            acc.add(
+                CompletionItem::new(
+                    CompletionKind::Attribute,
+                    ctx.source_range(),
+                    lint_completion.label,
+                )
+                .kind(CompletionItemKind::Attribute)
+                .detail(lint_completion.description),
+            );
+        }
+    }
+}
+
+fn parse_comma_sep_input(derive_input: ast::TokenTree) -> Result<FxHashSet<String>, ()> {
     match (derive_input.left_delimiter_token(), derive_input.right_delimiter_token()) {
         (Some(left_paren), Some(right_paren))
             if left_paren.kind() == SyntaxKind::L_PAREN
@@ -212,6 +237,7 @@ struct DeriveCompletion {
 
 /// Standard Rust derives and the information about their dependencies
 /// (the dependencies are needed so that the main derive don't break the compilation when added)
+#[rustfmt::skip]
 const DEFAULT_DERIVE_COMPLETIONS: &[DeriveCompletion] = &[
     DeriveCompletion { label: "Clone", dependencies: &[] },
     DeriveCompletion { label: "Copy", dependencies: &["Clone"] },
@@ -224,6 +250,130 @@ const DEFAULT_DERIVE_COMPLETIONS: &[DeriveCompletion] = &[
     DeriveCompletion { label: "Ord", dependencies: &["PartialOrd", "Eq", "PartialEq"] },
 ];
 
+struct LintCompletion {
+    label: &'static str,
+    description: &'static str,
+}
+
+#[rustfmt::skip]
+const DEFAULT_LINT_COMPLETIONS: &[LintCompletion] = &[
+    LintCompletion { label: "absolute_paths_not_starting_with_crate", description: r#"fully qualified paths that start with a module name instead of `crate`, `self`, or an extern crate name"# },
+    LintCompletion { label: "anonymous_parameters", description: r#"detects anonymous parameters"# },
+    LintCompletion { label: "box_pointers", description: r#"use of owned (Box type) heap memory"# },
+    LintCompletion { label: "deprecated_in_future", description: r#"detects use of items that will be deprecated in a future version"# },
+    LintCompletion { label: "elided_lifetimes_in_paths", description: r#"hidden lifetime parameters in types are deprecated"# },
+    LintCompletion { label: "explicit_outlives_requirements", description: r#"outlives requirements can be inferred"# },
+    LintCompletion { label: "indirect_structural_match", description: r#"pattern with const indirectly referencing non-structural-match type"# },
+    LintCompletion { label: "keyword_idents", description: r#"detects edition keywords being used as an identifier"# },
+    LintCompletion { label: "macro_use_extern_crate", description: r#"the `#[macro_use]` attribute is now deprecated in favor of using macros via the module system"# },
+    LintCompletion { label: "meta_variable_misuse", description: r#"possible meta-variable misuse at macro definition"# },
+    LintCompletion { label: "missing_copy_implementations", description: r#"detects potentially-forgotten implementations of `Copy`"# },
+    LintCompletion { label: "missing_crate_level_docs", description: r#"detects crates with no crate-level documentation"# },
+    LintCompletion { label: "missing_debug_implementations", description: r#"detects missing implementations of Debug"# },
+    LintCompletion { label: "missing_docs", description: r#"detects missing documentation for public members"# },
+    LintCompletion { label: "missing_doc_code_examples", description: r#"detects publicly-exported items without code samples in their documentation"# },
+    LintCompletion { label: "non_ascii_idents", description: r#"detects non-ASCII identifiers"# },
+    LintCompletion { label: "private_doc_tests", description: r#"detects code samples in docs of private items not documented by rustdoc"# },
+    LintCompletion { label: "single_use_lifetimes", description: r#"detects lifetime parameters that are only used once"# },
+    LintCompletion { label: "trivial_casts", description: r#"detects trivial casts which could be removed"# },
+    LintCompletion { label: "trivial_numeric_casts", description: r#"detects trivial casts of numeric types which could be removed"# },
+    LintCompletion { label: "unaligned_references", description: r#"detects unaligned references to fields of packed structs"# },
+    LintCompletion { label: "unreachable_pub", description: r#"`pub` items not reachable from crate root"# },
+    LintCompletion { label: "unsafe_code", description: r#"usage of `unsafe` code"# },
+    LintCompletion { label: "unsafe_op_in_unsafe_fn", description: r#"unsafe operations in unsafe functions without an explicit unsafe block are deprecated"# },
+    LintCompletion { label: "unstable_features", description: r#"enabling unstable features (deprecated. do not use)"# },
+    LintCompletion { label: "unused_crate_dependencies", description: r#"crate dependencies that are never used"# },
+    LintCompletion { label: "unused_extern_crates", description: r#"extern crates that are never used"# },
+    LintCompletion { label: "unused_import_braces", description: r#"unnecessary braces around an imported item"# },
+    LintCompletion { label: "unused_lifetimes", description: r#"detects lifetime parameters that are never used"# },
+    LintCompletion { label: "unused_qualifications", description: r#"detects unnecessarily qualified names"# },
+    LintCompletion { label: "unused_results", description: r#"unused result of an expression in a statement"# },
+    LintCompletion { label: "variant_size_differences", description: r#"detects enums with widely varying variant sizes"# },
+    LintCompletion { label: "array_into_iter", description: r#"detects calling `into_iter` on arrays"# },
+    LintCompletion { label: "asm_sub_register", description: r#"using only a subset of a register for inline asm inputs"# },
+    LintCompletion { label: "bare_trait_objects", description: r#"suggest using `dyn Trait` for trait objects"# },
+    LintCompletion { label: "bindings_with_variant_name", description: r#"detects pattern bindings with the same name as one of the matched variants"# },
+    LintCompletion { label: "cenum_impl_drop_cast", description: r#"a C-like enum implementing Drop is cast"# },
+    LintCompletion { label: "clashing_extern_declarations", description: r#"detects when an extern fn has been declared with the same name but different types"# },
+    LintCompletion { label: "coherence_leak_check", description: r#"distinct impls distinguished only by the leak-check code"# },
+    LintCompletion { label: "confusable_idents", description: r#"detects visually confusable pairs between identifiers"# },
+    LintCompletion { label: "dead_code", description: r#"detect unused, unexported items"# },
+    LintCompletion { label: "deprecated", description: r#"detects use of deprecated items"# },
+    LintCompletion { label: "ellipsis_inclusive_range_patterns", description: r#"`...` range patterns are deprecated"# },
+    LintCompletion { label: "exported_private_dependencies", description: r#"public interface leaks type from a private dependency"# },
+    LintCompletion { label: "illegal_floating_point_literal_pattern", description: r#"floating-point literals cannot be used in patterns"# },
+    LintCompletion { label: "improper_ctypes", description: r#"proper use of libc types in foreign modules"# },
+    LintCompletion { label: "improper_ctypes_definitions", description: r#"proper use of libc types in foreign item definitions"# },
+    LintCompletion { label: "incomplete_features", description: r#"incomplete features that may function improperly in some or all cases"# },
+    LintCompletion { label: "inline_no_sanitize", description: r#"detects incompatible use of `#[inline(always)]` and `#[no_sanitize(...)]`"# },
+    LintCompletion { label: "intra_doc_link_resolution_failure", description: r#"failures in resolving intra-doc link targets"# },
+    LintCompletion { label: "invalid_codeblock_attributes", description: r#"codeblock attribute looks a lot like a known one"# },
+    LintCompletion { label: "invalid_value", description: r#"an invalid value is being created (such as a NULL reference)"# },
+    LintCompletion { label: "irrefutable_let_patterns", description: r#"detects irrefutable patterns in if-let and while-let statements"# },
+    LintCompletion { label: "late_bound_lifetime_arguments", description: r#"detects generic lifetime arguments in path segments with late bound lifetime parameters"# },
+    LintCompletion { label: "mixed_script_confusables", description: r#"detects Unicode scripts whose mixed script confusables codepoints are solely used"# },
+    LintCompletion { label: "mutable_borrow_reservation_conflict", description: r#"reservation of a two-phased borrow conflicts with other shared borrows"# },
+    LintCompletion { label: "non_camel_case_types", description: r#"types, variants, traits and type parameters should have camel case names"# },
+    LintCompletion { label: "non_shorthand_field_patterns", description: r#"using `Struct { x: x }` instead of `Struct { x }` in a pattern"# },
+    LintCompletion { label: "non_snake_case", description: r#"variables, methods, functions, lifetime parameters and modules should have snake case names"# },
+    LintCompletion { label: "non_upper_case_globals", description: r#"static constants should have uppercase identifiers"# },
+    LintCompletion { label: "no_mangle_generic_items", description: r#"generic items must be mangled"# },
+    LintCompletion { label: "overlapping_patterns", description: r#"detects overlapping patterns"# },
+    LintCompletion { label: "path_statements", description: r#"path statements with no effect"# },
+    LintCompletion { label: "private_in_public", description: r#"detect private items in public interfaces not caught by the old implementation"# },
+    LintCompletion { label: "proc_macro_derive_resolution_fallback", description: r#"detects proc macro derives using inaccessible names from parent modules"# },
+    LintCompletion { label: "redundant_semicolons", description: r#"detects unnecessary trailing semicolons"# },
+    LintCompletion { label: "renamed_and_removed_lints", description: r#"lints that have been renamed or removed"# },
+    LintCompletion { label: "safe_packed_borrows", description: r#"safe borrows of fields of packed structs were erroneously allowed"# },
+    LintCompletion { label: "stable_features", description: r#"stable features found in `#[feature]` directive"# },
+    LintCompletion { label: "trivial_bounds", description: r#"these bounds don't depend on an type parameters"# },
+    LintCompletion { label: "type_alias_bounds", description: r#"bounds in type aliases are not enforced"# },
+    LintCompletion { label: "tyvar_behind_raw_pointer", description: r#"raw pointer to an inference variable"# },
+    LintCompletion { label: "uncommon_codepoints", description: r#"detects uncommon Unicode codepoints in identifiers"# },
+    LintCompletion { label: "unconditional_recursion", description: r#"functions that cannot return without calling themselves"# },
+    LintCompletion { label: "unknown_lints", description: r#"unrecognized lint attribute"# },
+    LintCompletion { label: "unnameable_test_items", description: r#"detects an item that cannot be named being marked as `#[test_case]`"# },
+    LintCompletion { label: "unreachable_code", description: r#"detects unreachable code paths"# },
+    LintCompletion { label: "unreachable_patterns", description: r#"detects unreachable patterns"# },
+    LintCompletion { label: "unstable_name_collisions", description: r#"detects name collision with an existing but unstable method"# },
+    LintCompletion { label: "unused_allocation", description: r#"detects unnecessary allocations that can be eliminated"# },
+    LintCompletion { label: "unused_assignments", description: r#"detect assignments that will never be read"# },
+    LintCompletion { label: "unused_attributes", description: r#"detects attributes that were not used by the compiler"# },
+    LintCompletion { label: "unused_braces", description: r#"unnecessary braces around an expression"# },
+    LintCompletion { label: "unused_comparisons", description: r#"comparisons made useless by limits of the types involved"# },
+    LintCompletion { label: "unused_doc_comments", description: r#"detects doc comments that aren't used by rustdoc"# },
+    LintCompletion { label: "unused_features", description: r#"unused features found in crate-level `#[feature]` directives"# },
+    LintCompletion { label: "unused_imports", description: r#"imports that are never used"# },
+    LintCompletion { label: "unused_labels", description: r#"detects labels that are never used"# },
+    LintCompletion { label: "unused_macros", description: r#"detects macros that were not used"# },
+    LintCompletion { label: "unused_must_use", description: r#"unused result of a type flagged as `#[must_use]`"# },
+    LintCompletion { label: "unused_mut", description: r#"detect mut variables which don't need to be mutable"# },
+    LintCompletion { label: "unused_parens", description: r#"`if`, `match`, `while` and `return` do not need parentheses"# },
+    LintCompletion { label: "unused_unsafe", description: r#"unnecessary use of an `unsafe` block"# },
+    LintCompletion { label: "unused_variables", description: r#"detect variables which are not used in any way"# },
+    LintCompletion { label: "warnings", description: r#"mass-change the level for lints which produce warnings"# },
+    LintCompletion { label: "where_clauses_object_safety", description: r#"checks the object safety of where clauses"# },
+    LintCompletion { label: "while_true", description: r#"suggest using `loop { }` instead of `while true { }`"# },
+    LintCompletion { label: "ambiguous_associated_items", description: r#"ambiguous associated items"# },
+    LintCompletion { label: "arithmetic_overflow", description: r#"arithmetic operation overflows"# },
+    LintCompletion { label: "conflicting_repr_hints", description: r#"conflicts between `#[repr(..)]` hints that were previously accepted and used in practice"# },
+    LintCompletion { label: "const_err", description: r#"constant evaluation detected erroneous expression"# },
+    LintCompletion { label: "ill_formed_attribute_input", description: r#"ill-formed attribute inputs that were previously accepted and used in practice"# },
+    LintCompletion { label: "incomplete_include", description: r#"trailing content in included file"# },
+    LintCompletion { label: "invalid_type_param_default", description: r#"type parameter default erroneously allowed in invalid location"# },
+    LintCompletion { label: "macro_expanded_macro_exports_accessed_by_absolute_paths", description: r#"macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths"# },
+    LintCompletion { label: "missing_fragment_specifier", description: r#"detects missing fragment specifiers in unused `macro_rules!` patterns"# },
+    LintCompletion { label: "mutable_transmutes", description: r#"mutating transmuted &mut T from &T may cause undefined behavior"# },
+    LintCompletion { label: "no_mangle_const_items", description: r#"const items will not have their symbols exported"# },
+    LintCompletion { label: "order_dependent_trait_objects", description: r#"trait-object types were treated as different depending on marker-trait order"# },
+    LintCompletion { label: "overflowing_literals", description: r#"literal out of range for its type"# },
+    LintCompletion { label: "patterns_in_fns_without_body", description: r#"patterns in functions without body were erroneously allowed"# },
+    LintCompletion { label: "pub_use_of_private_extern_crate", description: r#"detect public re-exports of private extern crates"# },
+    LintCompletion { label: "soft_unstable", description: r#"a feature gate that doesn't break dependent crates"# },
+    LintCompletion { label: "unconditional_panic", description: r#"operation will cause a panic at runtime"# },
+    LintCompletion { label: "unknown_crate_types", description: r#"unknown crate type found in `#[crate_type]` directive"# },
+];
+
 #[cfg(test)]
 mod tests {
     use expect::{expect, Expect};
@@ -257,6 +407,130 @@ struct Test {}
     }
 
     #[test]
+    fn empty_lint_completion() {
+        check(
+            r#"#[allow(<|>)]"#,
+            expect![[r#"
+                at absolute_paths_not_starting_with_crate fully qualified paths that start with a module name instead of `crate`, `self`, or an extern crate name
+                at ambiguous_associated_items ambiguous associated items
+                at anonymous_parameters detects anonymous parameters
+                at arithmetic_overflow arithmetic operation overflows
+                at array_into_iter  detects calling `into_iter` on arrays
+                at asm_sub_register using only a subset of a register for inline asm inputs
+                at bare_trait_objects suggest using `dyn Trait` for trait objects
+                at bindings_with_variant_name detects pattern bindings with the same name as one of the matched variants
+                at box_pointers     use of owned (Box type) heap memory
+                at cenum_impl_drop_cast a C-like enum implementing Drop is cast
+                at clashing_extern_declarations detects when an extern fn has been declared with the same name but different types
+                at coherence_leak_check distinct impls distinguished only by the leak-check code
+                at conflicting_repr_hints conflicts between `#[repr(..)]` hints that were previously accepted and used in practice
+                at confusable_idents detects visually confusable pairs between identifiers
+                at const_err        constant evaluation detected erroneous expression
+                at dead_code        detect unused, unexported items
+                at deprecated       detects use of deprecated items
+                at deprecated_in_future detects use of items that will be deprecated in a future version
+                at elided_lifetimes_in_paths hidden lifetime parameters in types are deprecated
+                at ellipsis_inclusive_range_patterns `...` range patterns are deprecated
+                at explicit_outlives_requirements outlives requirements can be inferred
+                at exported_private_dependencies public interface leaks type from a private dependency
+                at ill_formed_attribute_input ill-formed attribute inputs that were previously accepted and used in practice
+                at illegal_floating_point_literal_pattern floating-point literals cannot be used in patterns
+                at improper_ctypes  proper use of libc types in foreign modules
+                at improper_ctypes_definitions proper use of libc types in foreign item definitions
+                at incomplete_features incomplete features that may function improperly in some or all cases
+                at incomplete_include trailing content in included file
+                at indirect_structural_match pattern with const indirectly referencing non-structural-match type
+                at inline_no_sanitize detects incompatible use of `#[inline(always)]` and `#[no_sanitize(...)]`
+                at intra_doc_link_resolution_failure failures in resolving intra-doc link targets
+                at invalid_codeblock_attributes codeblock attribute looks a lot like a known one
+                at invalid_type_param_default type parameter default erroneously allowed in invalid location
+                at invalid_value    an invalid value is being created (such as a NULL reference)
+                at irrefutable_let_patterns detects irrefutable patterns in if-let and while-let statements
+                at keyword_idents   detects edition keywords being used as an identifier
+                at late_bound_lifetime_arguments detects generic lifetime arguments in path segments with late bound lifetime parameters
+                at macro_expanded_macro_exports_accessed_by_absolute_paths macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
+                at macro_use_extern_crate the `#[macro_use]` attribute is now deprecated in favor of using macros via the module system
+                at meta_variable_misuse possible meta-variable misuse at macro definition
+                at missing_copy_implementations detects potentially-forgotten implementations of `Copy`
+                at missing_crate_level_docs detects crates with no crate-level documentation
+                at missing_debug_implementations detects missing implementations of Debug
+                at missing_doc_code_examples detects publicly-exported items without code samples in their documentation
+                at missing_docs     detects missing documentation for public members
+                at missing_fragment_specifier detects missing fragment specifiers in unused `macro_rules!` patterns
+                at mixed_script_confusables detects Unicode scripts whose mixed script confusables codepoints are solely used
+                at mutable_borrow_reservation_conflict reservation of a two-phased borrow conflicts with other shared borrows
+                at mutable_transmutes mutating transmuted &mut T from &T may cause undefined behavior
+                at no_mangle_const_items const items will not have their symbols exported
+                at no_mangle_generic_items generic items must be mangled
+                at non_ascii_idents detects non-ASCII identifiers
+                at non_camel_case_types types, variants, traits and type parameters should have camel case names
+                at non_shorthand_field_patterns using `Struct { x: x }` instead of `Struct { x }` in a pattern
+                at non_snake_case   variables, methods, functions, lifetime parameters and modules should have snake case names
+                at non_upper_case_globals static constants should have uppercase identifiers
+                at order_dependent_trait_objects trait-object types were treated as different depending on marker-trait order
+                at overflowing_literals literal out of range for its type
+                at overlapping_patterns detects overlapping patterns
+                at path_statements  path statements with no effect
+                at patterns_in_fns_without_body patterns in functions without body were erroneously allowed
+                at private_doc_tests detects code samples in docs of private items not documented by rustdoc
+                at private_in_public detect private items in public interfaces not caught by the old implementation
+                at proc_macro_derive_resolution_fallback detects proc macro derives using inaccessible names from parent modules
+                at pub_use_of_private_extern_crate detect public re-exports of private extern crates
+                at redundant_semicolons detects unnecessary trailing semicolons
+                at renamed_and_removed_lints lints that have been renamed or removed
+                at safe_packed_borrows safe borrows of fields of packed structs were erroneously allowed
+                at single_use_lifetimes detects lifetime parameters that are only used once
+                at soft_unstable    a feature gate that doesn't break dependent crates
+                at stable_features  stable features found in `#[feature]` directive
+                at trivial_bounds   these bounds don't depend on an type parameters
+                at trivial_casts    detects trivial casts which could be removed
+                at trivial_numeric_casts detects trivial casts of numeric types which could be removed
+                at type_alias_bounds bounds in type aliases are not enforced
+                at tyvar_behind_raw_pointer raw pointer to an inference variable
+                at unaligned_references detects unaligned references to fields of packed structs
+                at uncommon_codepoints detects uncommon Unicode codepoints in identifiers
+                at unconditional_panic operation will cause a panic at runtime
+                at unconditional_recursion functions that cannot return without calling themselves
+                at unknown_crate_types unknown crate type found in `#[crate_type]` directive
+                at unknown_lints    unrecognized lint attribute
+                at unnameable_test_items detects an item that cannot be named being marked as `#[test_case]`
+                at unreachable_code detects unreachable code paths
+                at unreachable_patterns detects unreachable patterns
+                at unreachable_pub  `pub` items not reachable from crate root
+                at unsafe_code      usage of `unsafe` code
+                at unsafe_op_in_unsafe_fn unsafe operations in unsafe functions without an explicit unsafe block are deprecated
+                at unstable_features enabling unstable features (deprecated. do not use)
+                at unstable_name_collisions detects name collision with an existing but unstable method
+                at unused_allocation detects unnecessary allocations that can be eliminated
+                at unused_assignments detect assignments that will never be read
+                at unused_attributes detects attributes that were not used by the compiler
+                at unused_braces    unnecessary braces around an expression
+                at unused_comparisons comparisons made useless by limits of the types involved
+                at unused_crate_dependencies crate dependencies that are never used
+                at unused_doc_comments detects doc comments that aren't used by rustdoc
+                at unused_extern_crates extern crates that are never used
+                at unused_features  unused features found in crate-level `#[feature]` directives
+                at unused_import_braces unnecessary braces around an imported item
+                at unused_imports   imports that are never used
+                at unused_labels    detects labels that are never used
+                at unused_lifetimes detects lifetime parameters that are never used
+                at unused_macros    detects macros that were not used
+                at unused_must_use  unused result of a type flagged as `#[must_use]`
+                at unused_mut       detect mut variables which don't need to be mutable
+                at unused_parens    `if`, `match`, `while` and `return` do not need parentheses
+                at unused_qualifications detects unnecessarily qualified names
+                at unused_results   unused result of an expression in a statement
+                at unused_unsafe    unnecessary use of an `unsafe` block
+                at unused_variables detect variables which are not used in any way
+                at variant_size_differences detects enums with widely varying variant sizes
+                at warnings         mass-change the level for lints which produce warnings
+                at where_clauses_object_safety checks the object safety of where clauses
+                at while_true       suggest using `loop { }` instead of `while true { }`
+        "#]],
+        )
+    }
+
+    #[test]
     fn no_completion_for_incorrect_derive() {
         check(
             r#"
@@ -325,7 +599,7 @@ struct Test {}
 
     #[test]
     fn test_attribute_completion_inside_nested_attr() {
-        check(r#"#[allow(<|>)]"#, expect![[]])
+        check(r#"#[cfg(<|>)]"#, expect![[]])
     }
 
     #[test]
diff --git a/crates/ra_prof/src/memory_usage.rs b/crates/ra_prof/src/memory_usage.rs
index ee79ec3ee..745345fac 100644
--- a/crates/ra_prof/src/memory_usage.rs
+++ b/crates/ra_prof/src/memory_usage.rs
@@ -31,6 +31,12 @@ impl fmt::Display for MemoryUsage {
 #[derive(Default, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy)]
 pub struct Bytes(usize);
 
+impl Bytes {
+    pub fn megabytes(self) -> usize {
+        self.0 / 1024 / 1024
+    }
+}
+
 impl fmt::Display for Bytes {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let bytes = self.0;
diff --git a/crates/ra_ssr/src/lib.rs b/crates/ra_ssr/src/lib.rs
index 2fb326b45..7014a6ac6 100644
--- a/crates/ra_ssr/src/lib.rs
+++ b/crates/ra_ssr/src/lib.rs
@@ -51,8 +51,7 @@ pub struct MatchFinder<'db> {
     /// Our source of information about the user's code.
     sema: Semantics<'db, ra_ide_db::RootDatabase>,
     rules: Vec<ResolvedRule>,
-    scope: hir::SemanticsScope<'db>,
-    hygiene: hir::Hygiene,
+    resolution_scope: resolving::ResolutionScope<'db>,
 }
 
 impl<'db> MatchFinder<'db> {
@@ -63,21 +62,8 @@ impl<'db> MatchFinder<'db> {
         lookup_context: FilePosition,
     ) -> MatchFinder<'db> {
         let sema = Semantics::new(db);
-        let file = sema.parse(lookup_context.file_id);
-        // Find a node at the requested position, falling back to the whole file.
-        let node = file
-            .syntax()
-            .token_at_offset(lookup_context.offset)
-            .left_biased()
-            .map(|token| token.parent())
-            .unwrap_or_else(|| file.syntax().clone());
-        let scope = sema.scope(&node);
-        MatchFinder {
-            sema: Semantics::new(db),
-            rules: Vec::new(),
-            scope,
-            hygiene: hir::Hygiene::new(db, lookup_context.file_id.into()),
-        }
+        let resolution_scope = resolving::ResolutionScope::new(&sema, lookup_context);
+        MatchFinder { sema: Semantics::new(db), rules: Vec::new(), resolution_scope }
     }
 
     /// Constructs an instance using the start of the first file in `db` as the lookup context.
@@ -106,8 +92,7 @@ impl<'db> MatchFinder<'db> {
         for parsed_rule in rule.parsed_rules {
             self.rules.push(ResolvedRule::new(
                 parsed_rule,
-                &self.scope,
-                &self.hygiene,
+                &self.resolution_scope,
                 self.rules.len(),
             )?);
         }
@@ -140,8 +125,7 @@ impl<'db> MatchFinder<'db> {
         for parsed_rule in pattern.parsed_rules {
             self.rules.push(ResolvedRule::new(
                 parsed_rule,
-                &self.scope,
-                &self.hygiene,
+                &self.resolution_scope,
                 self.rules.len(),
             )?);
         }
diff --git a/crates/ra_ssr/src/resolving.rs b/crates/ra_ssr/src/resolving.rs
index 75f556785..123bd2bb2 100644
--- a/crates/ra_ssr/src/resolving.rs
+++ b/crates/ra_ssr/src/resolving.rs
@@ -3,10 +3,16 @@
 use crate::errors::error;
 use crate::{parsing, SsrError};
 use parsing::Placeholder;
+use ra_db::FilePosition;
 use ra_syntax::{ast, SmolStr, SyntaxKind, SyntaxNode, SyntaxToken};
 use rustc_hash::{FxHashMap, FxHashSet};
 use test_utils::mark;
 
+pub(crate) struct ResolutionScope<'db> {
+    scope: hir::SemanticsScope<'db>,
+    hygiene: hir::Hygiene,
+}
+
 pub(crate) struct ResolvedRule {
     pub(crate) pattern: ResolvedPattern,
     pub(crate) template: Option<ResolvedPattern>,
@@ -30,12 +36,11 @@ pub(crate) struct ResolvedPath {
 impl ResolvedRule {
     pub(crate) fn new(
         rule: parsing::ParsedRule,
-        scope: &hir::SemanticsScope,
-        hygiene: &hir::Hygiene,
+        resolution_scope: &ResolutionScope,
         index: usize,
     ) -> Result<ResolvedRule, SsrError> {
         let resolver =
-            Resolver { scope, hygiene, placeholders_by_stand_in: rule.placeholders_by_stand_in };
+            Resolver { resolution_scope, placeholders_by_stand_in: rule.placeholders_by_stand_in };
         let resolved_template = if let Some(template) = rule.template {
             Some(resolver.resolve_pattern_tree(template)?)
         } else {
@@ -57,8 +62,7 @@ impl ResolvedRule {
 }
 
 struct Resolver<'a, 'db> {
-    scope: &'a hir::SemanticsScope<'db>,
-    hygiene: &'a hir::Hygiene,
+    resolution_scope: &'a ResolutionScope<'db>,
     placeholders_by_stand_in: FxHashMap<SmolStr, parsing::Placeholder>,
 }
 
@@ -104,6 +108,7 @@ impl Resolver<'_, '_> {
                 && !self.path_contains_placeholder(&path)
             {
                 let resolution = self
+                    .resolution_scope
                     .resolve_path(&path)
                     .ok_or_else(|| error!("Failed to resolve path `{}`", node.text()))?;
                 resolved_paths.insert(node, ResolvedPath { resolution, depth });
@@ -131,9 +136,32 @@ impl Resolver<'_, '_> {
         }
         false
     }
+}
+
+impl<'db> ResolutionScope<'db> {
+    pub(crate) fn new(
+        sema: &hir::Semantics<'db, ra_ide_db::RootDatabase>,
+        lookup_context: FilePosition,
+    ) -> ResolutionScope<'db> {
+        use ra_syntax::ast::AstNode;
+        let file = sema.parse(lookup_context.file_id);
+        // Find a node at the requested position, falling back to the whole file.
+        let node = file
+            .syntax()
+            .token_at_offset(lookup_context.offset)
+            .left_biased()
+            .map(|token| token.parent())
+            .unwrap_or_else(|| file.syntax().clone());
+        let node = pick_node_for_resolution(node);
+        let scope = sema.scope(&node);
+        ResolutionScope {
+            scope,
+            hygiene: hir::Hygiene::new(sema.db, lookup_context.file_id.into()),
+        }
+    }
 
     fn resolve_path(&self, path: &ast::Path) -> Option<hir::PathResolution> {
-        let hir_path = hir::Path::from_src(path.clone(), self.hygiene)?;
+        let hir_path = hir::Path::from_src(path.clone(), &self.hygiene)?;
         // First try resolving the whole path. This will work for things like
         // `std::collections::HashMap`, but will fail for things like
         // `std::collections::HashMap::new`.
@@ -158,6 +186,33 @@ impl Resolver<'_, '_> {
     }
 }
 
+/// Returns a suitable node for resolving paths in the current scope. If we create a scope based on
+/// a statement node, then we can't resolve local variables that were defined in the current scope
+/// (only in parent scopes). So we find another node, ideally a child of the statement where local
+/// variable resolution is permitted.
+fn pick_node_for_resolution(node: SyntaxNode) -> SyntaxNode {
+    match node.kind() {
+        SyntaxKind::EXPR_STMT => {
+            if let Some(n) = node.first_child() {
+                mark::hit!(cursor_after_semicolon);
+                return n;
+            }
+        }
+        SyntaxKind::LET_STMT | SyntaxKind::BIND_PAT => {
+            if let Some(next) = node.next_sibling() {
+                return pick_node_for_resolution(next);
+            }
+        }
+        SyntaxKind::NAME => {
+            if let Some(parent) = node.parent() {
+                return pick_node_for_resolution(parent);
+            }
+        }
+        _ => {}
+    }
+    node
+}
+
 /// Returns whether `path` or any of its qualifiers contains type arguments.
 fn path_contains_type_arguments(path: Option<ast::Path>) -> bool {
     if let Some(path) = path {
diff --git a/crates/ra_ssr/src/tests.rs b/crates/ra_ssr/src/tests.rs
index b38807c0f..18ef2506a 100644
--- a/crates/ra_ssr/src/tests.rs
+++ b/crates/ra_ssr/src/tests.rs
@@ -885,3 +885,40 @@ fn ufcs_matches_method_call() {
         "#]],
     );
 }
+
+#[test]
+fn replace_local_variable_reference() {
+    // The pattern references a local variable `foo` in the block containing the cursor. We should
+    // only replace references to this variable `foo`, not other variables that just happen to have
+    // the same name.
+    mark::check!(cursor_after_semicolon);
+    assert_ssr_transform(
+        "foo + $a ==>> $a - foo",
+        r#"
+            fn bar1() -> i32 {
+                let mut res = 0;
+                let foo = 5;
+                res += foo + 1;
+                let foo = 10;
+                res += foo + 2;<|>
+                res += foo + 3;
+                let foo = 15;
+                res += foo + 4;
+                res
+            }
+            "#,
+        expect![[r#"
+            fn bar1() -> i32 {
+                let mut res = 0;
+                let foo = 5;
+                res += foo + 1;
+                let foo = 10;
+                res += 2 - foo;
+                res += 3 - foo;
+                let foo = 15;
+                res += foo + 4;
+                res
+            }
+        "#]],
+    )
+}
diff --git a/crates/rust-analyzer/src/cli.rs b/crates/rust-analyzer/src/cli.rs
index 753001949..a9b9c8923 100644
--- a/crates/rust-analyzer/src/cli.rs
+++ b/crates/rust-analyzer/src/cli.rs
@@ -74,3 +74,10 @@ fn read_stdin() -> Result<String> {
     std::io::stdin().read_to_string(&mut buff)?;
     Ok(buff)
 }
+
+fn report_metric(metric: &str, value: u64, unit: &str) {
+    if std::env::var("RA_METRICS").is_err() {
+        return;
+    }
+    println!("METRIC:{}:{}:{}", metric, value, unit)
+}
diff --git a/crates/rust-analyzer/src/cli/analysis_stats.rs b/crates/rust-analyzer/src/cli/analysis_stats.rs
index ddb3db6c3..ccc058682 100644
--- a/crates/rust-analyzer/src/cli/analysis_stats.rs
+++ b/crates/rust-analyzer/src/cli/analysis_stats.rs
@@ -3,26 +3,27 @@
 
 use std::{path::Path, time::Instant};
 
-use itertools::Itertools;
-use rand::{seq::SliceRandom, thread_rng};
-use rayon::prelude::*;
-use rustc_hash::FxHashSet;
-
 use hir::{
     db::{AstDatabase, DefDatabase, HirDatabase},
     original_range, AssocItem, Crate, HasSource, HirDisplay, ModuleDef,
 };
 use hir_def::FunctionId;
 use hir_ty::{Ty, TypeWalk};
+use itertools::Itertools;
 use ra_db::{
     salsa::{self, ParallelDatabase},
     SourceDatabaseExt,
 };
 use ra_syntax::AstNode;
+use rand::{seq::SliceRandom, thread_rng};
+use rayon::prelude::*;
+use rustc_hash::FxHashSet;
 use stdx::format_to;
 
 use crate::{
-    cli::{load_cargo::load_cargo, progress_report::ProgressReport, Result, Verbosity},
+    cli::{
+        load_cargo::load_cargo, progress_report::ProgressReport, report_metric, Result, Verbosity,
+    },
     print_memory_usage,
 };
 
@@ -48,7 +49,7 @@ pub fn analysis_stats(
     let db_load_time = Instant::now();
     let (host, vfs) = load_cargo(path, load_output_dirs, with_proc_macro)?;
     let db = host.raw_database();
-    println!("Database loaded {:?}", db_load_time.elapsed());
+    eprintln!("Database loaded {:?}", db_load_time.elapsed());
     let analysis_time = Instant::now();
     let mut num_crates = 0;
     let mut visited_modules = FxHashSet::default();
@@ -74,7 +75,7 @@ pub fn analysis_stats(
         visit_queue.shuffle(&mut thread_rng());
     }
 
-    println!("Crates in this dir: {}", num_crates);
+    eprintln!("Crates in this dir: {}", num_crates);
     let mut num_decls = 0;
     let mut funcs = Vec::new();
     while let Some(module) = visit_queue.pop() {
@@ -98,10 +99,15 @@ pub fn analysis_stats(
             }
         }
     }
-    println!("Total modules found: {}", visited_modules.len());
-    println!("Total declarations: {}", num_decls);
-    println!("Total functions: {}", funcs.len());
-    println!("Item Collection: {:?}, {}", analysis_time.elapsed(), ra_prof::memory_usage());
+    eprintln!("Total modules found: {}", visited_modules.len());
+    eprintln!("Total declarations: {}", num_decls);
+    eprintln!("Total functions: {}", funcs.len());
+    let item_collection_memory = ra_prof::memory_usage();
+    eprintln!(
+        "Item Collection: {:?}, {}",
+        analysis_time.elapsed(),
+        item_collection_memory.allocated
+    );
 
     if randomize {
         funcs.shuffle(&mut thread_rng());
@@ -123,7 +129,11 @@ pub fn analysis_stats(
                 snap.0.infer(f_id.into());
             })
             .count();
-        println!("Parallel Inference: {:?}, {}", inference_time.elapsed(), ra_prof::memory_usage());
+        eprintln!(
+            "Parallel Inference: {:?}, {}",
+            inference_time.elapsed(),
+            ra_prof::memory_usage().allocated
+        );
     }
 
     let inference_time = Instant::now();
@@ -260,20 +270,35 @@ pub fn analysis_stats(
         bar.inc(1);
     }
     bar.finish_and_clear();
-    println!("Total expressions: {}", num_exprs);
-    println!(
+    eprintln!("Total expressions: {}", num_exprs);
+    eprintln!(
         "Expressions of unknown type: {} ({}%)",
         num_exprs_unknown,
         if num_exprs > 0 { num_exprs_unknown * 100 / num_exprs } else { 100 }
     );
-    println!(
+    report_metric("unknown type", num_exprs_unknown, "#");
+
+    eprintln!(
         "Expressions of partially unknown type: {} ({}%)",
         num_exprs_partially_unknown,
         if num_exprs > 0 { num_exprs_partially_unknown * 100 / num_exprs } else { 100 }
     );
-    println!("Type mismatches: {}", num_type_mismatches);
-    println!("Inference: {:?}, {}", inference_time.elapsed(), ra_prof::memory_usage());
-    println!("Total: {:?}, {}", analysis_time.elapsed(), ra_prof::memory_usage());
+
+    eprintln!("Type mismatches: {}", num_type_mismatches);
+    report_metric("type mismatches", num_type_mismatches, "#");
+
+    let inference_time = inference_time.elapsed();
+    let total_memory = ra_prof::memory_usage();
+    eprintln!(
+        "Inference: {:?}, {}",
+        inference_time,
+        total_memory.allocated - item_collection_memory.allocated
+    );
+
+    let analysis_time = analysis_time.elapsed();
+    eprintln!("Total: {:?}, {}", analysis_time, total_memory);
+    report_metric("total time", analysis_time.as_millis() as u64, "ms");
+    report_metric("total memory", total_memory.allocated.megabytes() as u64, "MB");
 
     if memory_usage {
         print_memory_usage(host, vfs);
diff --git a/crates/rust-analyzer/src/lib.rs b/crates/rust-analyzer/src/lib.rs
index c4284556e..ed37992cd 100644
--- a/crates/rust-analyzer/src/lib.rs
+++ b/crates/rust-analyzer/src/lib.rs
@@ -86,6 +86,6 @@ fn print_memory_usage(mut host: AnalysisHost, vfs: Vfs) {
     mem.push(("Remaining".into(), ra_prof::memory_usage().allocated));
 
     for (name, bytes) in mem {
-        println!("{:>8} {}", bytes, name);
+        eprintln!("{:>8} {}", bytes, name);
     }
 }
diff --git a/crates/vfs/src/file_set.rs b/crates/vfs/src/file_set.rs
index e5e2ef530..e9196fcd2 100644
--- a/crates/vfs/src/file_set.rs
+++ b/crates/vfs/src/file_set.rs
@@ -148,25 +148,54 @@ impl fst::Automaton for PrefixOf<'_> {
     }
 }
 
-#[test]
-fn test_partitioning() {
-    let mut file_set = FileSetConfig::builder();
-    file_set.add_file_set(vec![VfsPath::new_virtual_path("/foo".into())]);
-    file_set.add_file_set(vec![VfsPath::new_virtual_path("/foo/bar/baz".into())]);
-    let file_set = file_set.build();
-
-    let mut vfs = Vfs::default();
-    vfs.set_file_contents(VfsPath::new_virtual_path("/foo/src/lib.rs".into()), Some(Vec::new()));
-    vfs.set_file_contents(
-        VfsPath::new_virtual_path("/foo/src/bar/baz/lib.rs".into()),
-        Some(Vec::new()),
-    );
-    vfs.set_file_contents(
-        VfsPath::new_virtual_path("/foo/bar/baz/lib.rs".into()),
-        Some(Vec::new()),
-    );
-    vfs.set_file_contents(VfsPath::new_virtual_path("/quux/lib.rs".into()), Some(Vec::new()));
-
-    let partition = file_set.partition(&vfs).into_iter().map(|it| it.len()).collect::<Vec<_>>();
-    assert_eq!(partition, vec![2, 1, 1]);
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn path_prefix() {
+        let mut file_set = FileSetConfig::builder();
+        file_set.add_file_set(vec![VfsPath::new_virtual_path("/foo".into())]);
+        file_set.add_file_set(vec![VfsPath::new_virtual_path("/foo/bar/baz".into())]);
+        let file_set = file_set.build();
+
+        let mut vfs = Vfs::default();
+        vfs.set_file_contents(
+            VfsPath::new_virtual_path("/foo/src/lib.rs".into()),
+            Some(Vec::new()),
+        );
+        vfs.set_file_contents(
+            VfsPath::new_virtual_path("/foo/src/bar/baz/lib.rs".into()),
+            Some(Vec::new()),
+        );
+        vfs.set_file_contents(
+            VfsPath::new_virtual_path("/foo/bar/baz/lib.rs".into()),
+            Some(Vec::new()),
+        );
+        vfs.set_file_contents(VfsPath::new_virtual_path("/quux/lib.rs".into()), Some(Vec::new()));
+
+        let partition = file_set.partition(&vfs).into_iter().map(|it| it.len()).collect::<Vec<_>>();
+        assert_eq!(partition, vec![2, 1, 1]);
+    }
+
+    #[test]
+    fn name_prefix() {
+        let mut file_set = FileSetConfig::builder();
+        file_set.add_file_set(vec![VfsPath::new_virtual_path("/foo".into())]);
+        file_set.add_file_set(vec![VfsPath::new_virtual_path("/foo-things".into())]);
+        let file_set = file_set.build();
+
+        let mut vfs = Vfs::default();
+        vfs.set_file_contents(
+            VfsPath::new_virtual_path("/foo/src/lib.rs".into()),
+            Some(Vec::new()),
+        );
+        vfs.set_file_contents(
+            VfsPath::new_virtual_path("/foo-things/src/lib.rs".into()),
+            Some(Vec::new()),
+        );
+
+        let partition = file_set.partition(&vfs).into_iter().map(|it| it.len()).collect::<Vec<_>>();
+        assert_eq!(partition, vec![1, 1, 0]);
+    }
 }