13 files changed, 406 insertions, 116 deletions

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index dea552a60..b2ce7ca3c 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -125,12 +125,20 @@ impl Attrs {
         AttrQuery { attrs: self, key }
     }
 
-    pub fn cfg(&self) -> impl Iterator<Item = CfgExpr> + '_ {
+    pub fn cfg(&self) -> Option<CfgExpr> {
         // FIXME: handle cfg_attr :-)
-        self.by_key("cfg").tt_values().map(CfgExpr::parse)
+        let mut cfgs = self.by_key("cfg").tt_values().map(CfgExpr::parse).collect::<Vec<_>>();
+        match cfgs.len() {
+            0 => None,
+            1 => Some(cfgs.pop().unwrap()),
+            _ => Some(CfgExpr::All(cfgs)),
+        }
     }
     pub(crate) fn is_cfg_enabled(&self, cfg_options: &CfgOptions) -> bool {
-        self.cfg().all(|cfg| cfg_options.check(&cfg) != Some(false))
+        match self.cfg() {
+            None => true,
+            Some(cfg) => cfg_options.check(&cfg) != Some(false),
+        }
     }
 }
 
diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
index 9a9a605dd..d10b1af01 100644
--- a/crates/hir_def/src/body.rs
+++ b/crates/hir_def/src/body.rs
@@ -1,6 +1,9 @@
 //! Defines `Body`: a lowered representation of bodies of functions, statics and
 //! consts.
 mod lower;
+mod diagnostics;
+#[cfg(test)]
+mod tests;
 pub mod scope;
 
 use std::{mem, ops::Index, sync::Arc};
@@ -10,7 +13,10 @@ use base_db::CrateId;
 use cfg::CfgOptions;
 use drop_bomb::DropBomb;
 use either::Either;
-use hir_expand::{ast_id_map::AstIdMap, hygiene::Hygiene, AstId, HirFileId, InFile, MacroDefId};
+use hir_expand::{
+    ast_id_map::AstIdMap, diagnostics::DiagnosticSink, hygiene::Hygiene, AstId, HirFileId, InFile,
+    MacroDefId,
+};
 use rustc_hash::FxHashMap;
 use syntax::{ast, AstNode, AstPtr};
 use test_utils::mark;
@@ -105,14 +111,16 @@ impl Expander {
 
         let macro_call = InFile::new(self.current_file_id, &macro_call);
 
-        if let Some(call_id) = macro_call.as_call_id(db, self.crate_def_map.krate, |path| {
+        let resolver = |path: ModPath| -> Option<MacroDefId> {
             if let Some(local_scope) = local_scope {
                 if let Some(def) = path.as_ident().and_then(|n| local_scope.get_legacy_macro(n)) {
                     return Some(def);
                 }
             }
             self.resolve_path_as_macro(db, &path)
-        }) {
+        };
+
+        if let Some(call_id) = macro_call.as_call_id(db, self.crate_def_map.krate, resolver) {
             let file_id = call_id.as_file();
             if let Some(node) = db.parse_or_expand(file_id) {
                 if let Some(expr) = T::cast(node) {
@@ -148,8 +156,12 @@ impl Expander {
         InFile { file_id: self.current_file_id, value }
     }
 
-    pub(crate) fn is_cfg_enabled(&self, owner: &dyn ast::AttrsOwner) -> bool {
-        self.cfg_expander.is_cfg_enabled(owner)
+    pub(crate) fn parse_attrs(&self, owner: &dyn ast::AttrsOwner) -> Attrs {
+        self.cfg_expander.parse_attrs(owner)
+    }
+
+    pub(crate) fn cfg_options(&self) -> &CfgOptions {
+        &self.cfg_expander.cfg_options
     }
 
     fn parse_path(&mut self, path: ast::Path) -> Option<Path> {
@@ -217,6 +229,10 @@ pub struct BodySourceMap {
     pat_map_back: ArenaMap<PatId, Result<PatSource, SyntheticSyntax>>,
     field_map: FxHashMap<(ExprId, usize), InFile<AstPtr<ast::RecordExprField>>>,
     expansions: FxHashMap<InFile<AstPtr<ast::MacroCall>>, HirFileId>,
+
+    /// Diagnostics accumulated during body lowering. These contain `AstPtr`s and so are stored in
+    /// the source map (since they're just as volatile).
+    diagnostics: Vec<diagnostics::BodyDiagnostic>,
 }
 
 #[derive(Default, Debug, Eq, PartialEq, Clone, Copy)]
@@ -316,45 +332,10 @@ impl BodySourceMap {
     pub fn field_syntax(&self, expr: ExprId, field: usize) -> InFile<AstPtr<ast::RecordExprField>> {
         self.field_map[&(expr, field)].clone()
     }
-}
 
-#[cfg(test)]
-mod tests {
-    use base_db::{fixture::WithFixture, SourceDatabase};
-    use test_utils::mark;
-
-    use crate::ModuleDefId;
-
-    use super::*;
-
-    fn lower(ra_fixture: &str) -> Arc<Body> {
-        let (db, file_id) = crate::test_db::TestDB::with_single_file(ra_fixture);
-
-        let krate = db.crate_graph().iter().next().unwrap();
-        let def_map = db.crate_def_map(krate);
-        let module = def_map.modules_for_file(file_id).next().unwrap();
-        let module = &def_map[module];
-        let fn_def = match module.scope.declarations().next().unwrap() {
-            ModuleDefId::FunctionId(it) => it,
-            _ => panic!(),
-        };
-
-        db.body(fn_def.into())
-    }
-
-    #[test]
-    fn your_stack_belongs_to_me() {
-        mark::check!(your_stack_belongs_to_me);
-        lower(
-            "
-macro_rules! n_nuple {
-    ($e:tt) => ();
-    ($($rest:tt)*) => {{
-        (n_nuple!($($rest)*)None,)
-    }};
-}
-fn main() { n_nuple!(1,2,3); }
-",
-        );
+    pub(crate) fn add_diagnostics(&self, _db: &dyn DefDatabase, sink: &mut DiagnosticSink<'_>) {
+        for diag in &self.diagnostics {
+            diag.add_to(sink);
+        }
     }
 }
diff --git a/crates/hir_def/src/body/diagnostics.rs b/crates/hir_def/src/body/diagnostics.rs
new file mode 100644
index 000000000..cfa47d189
--- /dev/null
+++ b/crates/hir_def/src/body/diagnostics.rs
@@ -0,0 +1,20 @@
+//! Diagnostics emitted during body lowering.
+
+use hir_expand::diagnostics::DiagnosticSink;
+
+use crate::diagnostics::InactiveCode;
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum BodyDiagnostic {
+    InactiveCode(InactiveCode),
+}
+
+impl BodyDiagnostic {
+    pub fn add_to(&self, sink: &mut DiagnosticSink<'_>) {
+        match self {
+            BodyDiagnostic::InactiveCode(diag) => {
+                sink.push(diag.clone());
+            }
+        }
+    }
+}
diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 01e72690a..ddc267b83 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -16,7 +16,7 @@ use syntax::{
         self, ArgListOwner, ArrayExprKind, AstChildren, LiteralKind, LoopBodyOwner, NameOwner,
         SlicePatComponents,
     },
-    AstNode, AstPtr,
+    AstNode, AstPtr, SyntaxNodePtr,
 };
 use test_utils::mark;
 
@@ -25,6 +25,7 @@ use crate::{
     body::{Body, BodySourceMap, Expander, PatPtr, SyntheticSyntax},
     builtin_type::{BuiltinFloat, BuiltinInt},
     db::DefDatabase,
+    diagnostics::InactiveCode,
     expr::{
         dummy_expr_id, ArithOp, Array, BinaryOp, BindingAnnotation, CmpOp, Expr, ExprId, Literal,
         LogicOp, MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField, Statement,
@@ -37,7 +38,7 @@ use crate::{
     StaticLoc, StructLoc, TraitLoc, TypeAliasLoc, UnionLoc,
 };
 
-use super::{ExprSource, PatSource};
+use super::{diagnostics::BodyDiagnostic, ExprSource, PatSource};
 
 pub(crate) struct LowerCtx {
     hygiene: Hygiene,
@@ -176,7 +177,7 @@ impl ExprCollector<'_> {
 
     fn collect_expr(&mut self, expr: ast::Expr) -> ExprId {
         let syntax_ptr = AstPtr::new(&expr);
-        if !self.expander.is_cfg_enabled(&expr) {
+        if self.check_cfg(&expr).is_none() {
             return self.missing_expr();
         }
 
@@ -354,13 +355,15 @@ impl ExprCollector<'_> {
                 let arms = if let Some(match_arm_list) = e.match_arm_list() {
                     match_arm_list
                         .arms()
-                        .map(|arm| MatchArm {
-                            pat: self.collect_pat_opt(arm.pat()),
-                            expr: self.collect_expr_opt(arm.expr()),
-                            guard: arm
-                                .guard()
-                                .and_then(|guard| guard.expr())
-                                .map(|e| self.collect_expr(e)),
+                        .filter_map(|arm| {
+                            self.check_cfg(&arm).map(|()| MatchArm {
+                                pat: self.collect_pat_opt(arm.pat()),
+                                expr: self.collect_expr_opt(arm.expr()),
+                                guard: arm
+                                    .guard()
+                                    .and_then(|guard| guard.expr())
+                                    .map(|e| self.collect_expr(e)),
+                            })
                         })
                         .collect()
                 } else {
@@ -406,9 +409,8 @@ impl ExprCollector<'_> {
                         .fields()
                         .inspect(|field| field_ptrs.push(AstPtr::new(field)))
                         .filter_map(|field| {
-                            if !self.expander.is_cfg_enabled(&field) {
-                                return None;
-                            }
+                            self.check_cfg(&field)?;
+
                             let name = field.field_name()?.as_name();
 
                             Some(RecordLitField {
@@ -620,15 +622,23 @@ impl ExprCollector<'_> {
             .filter_map(|s| {
                 let stmt = match s {
                     ast::Stmt::LetStmt(stmt) => {
+                        self.check_cfg(&stmt)?;
+
                         let pat = self.collect_pat_opt(stmt.pat());
                         let type_ref = stmt.ty().map(|it| TypeRef::from_ast(&self.ctx(), it));
                         let initializer = stmt.initializer().map(|e| self.collect_expr(e));
                         Statement::Let { pat, type_ref, initializer }
                     }
                     ast::Stmt::ExprStmt(stmt) => {
+                        self.check_cfg(&stmt)?;
+
                         Statement::Expr(self.collect_expr_opt(stmt.expr()))
                     }
-                    ast::Stmt::Item(_) => return None,
+                    ast::Stmt::Item(item) => {
+                        self.check_cfg(&item)?;
+
+                        return None;
+                    }
                 };
                 Some(stmt)
             })
@@ -872,6 +882,28 @@ impl ExprCollector<'_> {
 
         (args, ellipsis)
     }
+
+    /// Returns `None` (and emits diagnostics) when `owner` if `#[cfg]`d out, and `Some(())` when
+    /// not.
+    fn check_cfg(&mut self, owner: &dyn ast::AttrsOwner) -> Option<()> {
+        match self.expander.parse_attrs(owner).cfg() {
+            Some(cfg) => {
+                if self.expander.cfg_options().check(&cfg) != Some(false) {
+                    return Some(());
+                }
+
+                self.source_map.diagnostics.push(BodyDiagnostic::InactiveCode(InactiveCode {
+                    file: self.expander.current_file_id,
+                    node: SyntaxNodePtr::new(owner.syntax()),
+                    cfg,
+                    opts: self.expander.cfg_options().clone(),
+                }));
+
+                None
+            }
+            None => Some(()),
+        }
+    }
 }
 
 impl From<ast::BinOp> for BinaryOp {
diff --git a/crates/hir_def/src/body/tests.rs b/crates/hir_def/src/body/tests.rs
new file mode 100644
index 000000000..f07df5cee
--- /dev/null
+++ b/crates/hir_def/src/body/tests.rs
@@ -0,0 +1,75 @@
+use base_db::{fixture::WithFixture, SourceDatabase};
+use test_utils::mark;
+
+use crate::{test_db::TestDB, ModuleDefId};
+
+use super::*;
+
+fn lower(ra_fixture: &str) -> Arc<Body> {
+    let (db, file_id) = crate::test_db::TestDB::with_single_file(ra_fixture);
+
+    let krate = db.crate_graph().iter().next().unwrap();
+    let def_map = db.crate_def_map(krate);
+    let module = def_map.modules_for_file(file_id).next().unwrap();
+    let module = &def_map[module];
+    let fn_def = match module.scope.declarations().next().unwrap() {
+        ModuleDefId::FunctionId(it) => it,
+        _ => panic!(),
+    };
+
+    db.body(fn_def.into())
+}
+
+fn check_diagnostics(ra_fixture: &str) {
+    let db: TestDB = TestDB::with_files(ra_fixture);
+    db.check_diagnostics();
+}
+
+#[test]
+fn your_stack_belongs_to_me() {
+    mark::check!(your_stack_belongs_to_me);
+    lower(
+        "
+macro_rules! n_nuple {
+    ($e:tt) => ();
+    ($($rest:tt)*) => {{
+        (n_nuple!($($rest)*)None,)
+    }};
+}
+fn main() { n_nuple!(1,2,3); }
+",
+    );
+}
+
+#[test]
+fn cfg_diagnostics() {
+    check_diagnostics(
+        r"
+fn f() {
+    // The three g̶e̶n̶d̶e̶r̶s̶ statements:
+
+    #[cfg(a)] fn f() {}  // Item statement
+  //^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+    #[cfg(a)] {}         // Expression statement
+  //^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+    #[cfg(a)] let x = 0; // let statement
+  //^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+
+    abc(#[cfg(a)] 0);
+      //^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+    let x = Struct {
+        #[cfg(a)] f: 0,
+      //^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+    };
+    match () {
+        () => (),
+        #[cfg(a)] () => (),
+      //^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+    }
+
+    #[cfg(a)] 0          // Trailing expression of block
+  //^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+}
+    ",
+    );
+}
diff --git a/crates/hir_def/src/diagnostics.rs b/crates/hir_def/src/diagnostics.rs
index 001b3c5db..b221b290c 100644
--- a/crates/hir_def/src/diagnostics.rs
+++ b/crates/hir_def/src/diagnostics.rs
@@ -1,12 +1,23 @@
 //! Diagnostics produced by `hir_def`.
 
 use std::any::Any;
+use stdx::format_to;
 
-use hir_expand::diagnostics::{Diagnostic, DiagnosticCode};
+use cfg::{CfgExpr, CfgOptions, DnfExpr};
+use hir_expand::diagnostics::{Diagnostic, DiagnosticCode, DiagnosticSink};
+use hir_expand::{HirFileId, InFile};
 use syntax::{ast, AstPtr, SyntaxNodePtr};
 
-use hir_expand::{HirFileId, InFile};
+use crate::{db::DefDatabase, DefWithBodyId};
 
+pub fn validate_body(db: &dyn DefDatabase, owner: DefWithBodyId, sink: &mut DiagnosticSink<'_>) {
+    let source_map = db.body_with_source_map(owner).1;
+    source_map.add_diagnostics(db, sink);
+}
+
+// Diagnostic: unresolved-module
+//
+// This diagnostic is triggered if rust-analyzer is unable to discover referred module.
 #[derive(Debug)]
 pub struct UnresolvedModule {
     pub file: HirFileId,
@@ -29,6 +40,9 @@ impl Diagnostic for UnresolvedModule {
     }
 }
 
+// Diagnostic: unresolved-extern-crate
+//
+// This diagnostic is triggered if rust-analyzer is unable to discover referred extern crate.
 #[derive(Debug)]
 pub struct UnresolvedExternCrate {
     pub file: HirFileId,
@@ -50,6 +64,9 @@ impl Diagnostic for UnresolvedExternCrate {
     }
 }
 
+// Diagnostic: unresolved-import
+//
+// This diagnostic is triggered if rust-analyzer is unable to discover imported module.
 #[derive(Debug)]
 pub struct UnresolvedImport {
     pub file: HirFileId,
@@ -77,3 +94,36 @@ impl Diagnostic for UnresolvedImport {
         true
     }
 }
+
+// Diagnostic: inactive-code
+//
+// This diagnostic is shown for code with inactive `#[cfg]` attributes.
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub struct InactiveCode {
+    pub file: HirFileId,
+    pub node: SyntaxNodePtr,
+    pub cfg: CfgExpr,
+    pub opts: CfgOptions,
+}
+
+impl Diagnostic for InactiveCode {
+    fn code(&self) -> DiagnosticCode {
+        DiagnosticCode("inactive-code")
+    }
+    fn message(&self) -> String {
+        let inactive = DnfExpr::new(self.cfg.clone()).why_inactive(&self.opts);
+        let mut buf = "code is inactive due to #[cfg] directives".to_string();
+
+        if let Some(inactive) = inactive {
+            format_to!(buf, ": {}", inactive);
+        }
+
+        buf
+    }
+    fn display_source(&self) -> InFile<SyntaxNodePtr> {
+        InFile::new(self.file, self.node.clone())
+    }
+    fn as_any(&self) -> &(dyn Any + Send + 'static) {
+        self
+    }
+}
diff --git a/crates/hir_def/src/import_map.rs b/crates/hir_def/src/import_map.rs
index 028cae2e7..1e24f29a8 100644
--- a/crates/hir_def/src/import_map.rs
+++ b/crates/hir_def/src/import_map.rs
@@ -356,7 +356,7 @@ mod tests {
         let krate = crate_graph
             .iter()
             .find(|krate| {
-                crate_graph[*krate].declaration_name.as_ref().map(|n| n.to_string())
+                crate_graph[*krate].display_name.as_ref().map(|n| n.to_string())
                     == Some(crate_name.to_string())
             })
             .unwrap();
@@ -375,7 +375,7 @@ mod tests {
                     let path = map.path_of(item).unwrap();
                     format!(
                         "{}::{} ({})\n",
-                        crate_graph[krate].declaration_name.as_ref().unwrap(),
+                        crate_graph[krate].display_name.as_ref().unwrap(),
                         path,
                         mark
                     )
@@ -416,7 +416,7 @@ mod tests {
             .iter()
             .filter_map(|krate| {
                 let cdata = &crate_graph[krate];
-                let name = cdata.declaration_name.as_ref()?;
+                let name = cdata.display_name.as_ref()?;
 
                 let map = db.import_map(krate);
 
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index 8a1121bbd..7eb388bae 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -672,6 +672,24 @@ impl ModItem {
     pub fn downcast<N: ItemTreeNode>(self) -> Option<FileItemTreeId<N>> {
         N::id_from_mod_item(self)
     }
+
+    pub fn ast_id(&self, tree: &ItemTree) -> FileAstId<ast::Item> {
+        match self {
+            ModItem::Import(it) => tree[it.index].ast_id().upcast(),
+            ModItem::ExternCrate(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Function(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Struct(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Union(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Enum(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Const(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Static(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Trait(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Impl(it) => tree[it.index].ast_id().upcast(),
+            ModItem::TypeAlias(it) => tree[it.index].ast_id().upcast(),
+            ModItem::Mod(it) => tree[it.index].ast_id().upcast(),
+            ModItem::MacroCall(it) => tree[it.index].ast_id().upcast(),
+        }
+    }
 }
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 3328639cf..ca7fb4a43 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -3,7 +3,7 @@
 use std::{collections::hash_map::Entry, mem, sync::Arc};
 
 use arena::map::ArenaMap;
-use hir_expand::{ast_id_map::AstIdMap, hygiene::Hygiene, HirFileId};
+use hir_expand::{ast_id_map::AstIdMap, hygiene::Hygiene, name::known, HirFileId};
 use smallvec::SmallVec;
 use syntax::{
     ast::{self, ModuleItemOwner},
@@ -555,7 +555,8 @@ impl Ctx {
                     let id: ModItem = match item {
                         ast::ExternItem::Fn(ast) => {
                             let func = self.lower_function(&ast)?;
-                            self.data().functions[func.index].is_unsafe = true;
+                            self.data().functions[func.index].is_unsafe =
+                                is_intrinsic_fn_unsafe(&self.data().functions[func.index].name);
                             func.into()
                         }
                         ast::ExternItem::Static(ast) => {
@@ -713,3 +714,45 @@ enum GenericsOwner<'a> {
     TypeAlias,
     Impl,
 }
+
+/// Returns `true` if the given intrinsic is unsafe to call, or false otherwise.
+fn is_intrinsic_fn_unsafe(name: &Name) -> bool {
+    // Should be kept in sync with https://github.com/rust-lang/rust/blob/c6e4db620a7d2f569f11dcab627430921ea8aacf/compiler/rustc_typeck/src/check/intrinsic.rs#L68
+    ![
+        known::abort,
+        known::min_align_of,
+        known::needs_drop,
+        known::caller_location,
+        known::size_of_val,
+        known::min_align_of_val,
+        known::add_with_overflow,
+        known::sub_with_overflow,
+        known::mul_with_overflow,
+        known::wrapping_add,
+        known::wrapping_sub,
+        known::wrapping_mul,
+        known::saturating_add,
+        known::saturating_sub,
+        known::rotate_left,
+        known::rotate_right,
+        known::ctpop,
+        known::ctlz,
+        known::cttz,
+        known::bswap,
+        known::bitreverse,
+        known::discriminant_value,
+        known::type_id,
+        known::likely,
+        known::unlikely,
+        known::ptr_guaranteed_eq,
+        known::ptr_guaranteed_ne,
+        known::minnumf32,
+        known::minnumf64,
+        known::maxnumf32,
+        known::rustc_peek,
+        known::maxnumf64,
+        known::type_name,
+        known::variant_count,
+    ]
+    .contains(&name)
+}
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 464ffef21..eb41d324e 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -172,11 +172,7 @@ pub struct ModuleData {
 impl CrateDefMap {
     pub(crate) fn crate_def_map_query(db: &dyn DefDatabase, krate: CrateId) -> Arc<CrateDefMap> {
         let _p = profile::span("crate_def_map_query").detail(|| {
-            db.crate_graph()[krate]
-                .declaration_name
-                .as_ref()
-                .map(ToString::to_string)
-                .unwrap_or_default()
+            db.crate_graph()[krate].display_name.as_deref().unwrap_or_default().to_string()
         });
         let def_map = {
             let edition = db.crate_graph()[krate].edition;
@@ -287,10 +283,11 @@ pub enum ModuleSource {
 }
 
 mod diagnostics {
+    use cfg::{CfgExpr, CfgOptions};
     use hir_expand::diagnostics::DiagnosticSink;
     use hir_expand::hygiene::Hygiene;
     use hir_expand::InFile;
-    use syntax::{ast, AstPtr};
+    use syntax::{ast, AstPtr, SyntaxNodePtr};
 
     use crate::path::ModPath;
     use crate::{db::DefDatabase, diagnostics::*, nameres::LocalModuleId, AstId};
@@ -302,6 +299,8 @@ mod diagnostics {
         UnresolvedExternCrate { ast: AstId<ast::ExternCrate> },
 
         UnresolvedImport { ast: AstId<ast::Use>, index: usize },
+
+        UnconfiguredCode { ast: InFile<SyntaxNodePtr>, cfg: CfgExpr, opts: CfgOptions },
     }
 
     #[derive(Debug, PartialEq, Eq)]
@@ -340,6 +339,15 @@ mod diagnostics {
             Self { in_module: container, kind: DiagnosticKind::UnresolvedImport { ast, index } }
         }
 
+        pub(super) fn unconfigured_code(
+            container: LocalModuleId,
+            ast: InFile<SyntaxNodePtr>,
+            cfg: CfgExpr,
+            opts: CfgOptions,
+        ) -> Self {
+            Self { in_module: container, kind: DiagnosticKind::UnconfiguredCode { ast, cfg, opts } }
+        }
+
         pub(super) fn add_to(
             &self,
             db: &dyn DefDatabase,
@@ -389,6 +397,15 @@ mod diagnostics {
                         sink.push(UnresolvedImport { file: ast.file_id, node: AstPtr::new(&tree) });
                     }
                 }
+
+                DiagnosticKind::UnconfiguredCode { ast, cfg, opts } => {
+                    sink.push(InactiveCode {
+                        file: ast.file_id,
+                        node: ast.value.clone(),
+                        cfg: cfg.clone(),
+                        opts: opts.clone(),
+                    });
+                }
             }
         }
     }
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index c8cd04264..f30172d90 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -6,7 +6,7 @@
 use std::iter;
 
 use base_db::{CrateId, FileId, ProcMacroId};
-use cfg::CfgOptions;
+use cfg::{CfgExpr, CfgOptions};
 use hir_expand::InFile;
 use hir_expand::{
     ast_id_map::FileAstId,
@@ -900,7 +900,8 @@ impl ModCollector<'_, '_> {
         // `#[macro_use] extern crate` is hoisted to imports macros before collecting
         // any other items.
         for item in items {
-            if self.is_cfg_enabled(self.item_tree.attrs((*item).into())) {
+            let attrs = self.item_tree.attrs((*item).into());
+            if attrs.cfg().map_or(true, |cfg| self.is_cfg_enabled(&cfg)) {
                 if let ModItem::ExternCrate(id) = item {
                     let import = self.item_tree[*id].clone();
                     if import.is_macro_use {
@@ -912,8 +913,11 @@ impl ModCollector<'_, '_> {
 
         for &item in items {
             let attrs = self.item_tree.attrs(item.into());
-            if !self.is_cfg_enabled(attrs) {
-                continue;
+            if let Some(cfg) = attrs.cfg() {
+                if !self.is_cfg_enabled(&cfg) {
+                    self.emit_unconfigured_diagnostic(item, &cfg);
+                    continue;
+                }
             }
             let module =
                 ModuleId { krate: self.def_collector.def_map.krate, local_id: self.module_id };
@@ -1320,8 +1324,22 @@ impl ModCollector<'_, '_> {
         }
     }
 
-    fn is_cfg_enabled(&self, attrs: &Attrs) -> bool {
-        attrs.is_cfg_enabled(self.def_collector.cfg_options)
+    fn is_cfg_enabled(&self, cfg: &CfgExpr) -> bool {
+        self.def_collector.cfg_options.check(cfg) != Some(false)
+    }
+
+    fn emit_unconfigured_diagnostic(&mut self, item: ModItem, cfg: &CfgExpr) {
+        let ast_id = item.ast_id(self.item_tree);
+        let id_map = self.def_collector.db.ast_id_map(self.file_id);
+        let syntax_ptr = id_map.get(ast_id).syntax_node_ptr();
+
+        let ast_node = InFile::new(self.file_id, syntax_ptr);
+        self.def_collector.def_map.diagnostics.push(DefDiagnostic::unconfigured_code(
+            self.module_id,
+            ast_node,
+            cfg.clone(),
+            self.def_collector.cfg_options.clone(),
+        ));
     }
 }
 
diff --git a/crates/hir_def/src/nameres/tests/diagnostics.rs b/crates/hir_def/src/nameres/tests/diagnostics.rs
index 576b813d2..1a7b98831 100644
--- a/crates/hir_def/src/nameres/tests/diagnostics.rs
+++ b/crates/hir_def/src/nameres/tests/diagnostics.rs
@@ -1,42 +1,10 @@
 use base_db::fixture::WithFixture;
-use base_db::FileId;
-use base_db::SourceDatabaseExt;
-use hir_expand::db::AstDatabase;
-use rustc_hash::FxHashMap;
-use syntax::TextRange;
-use syntax::TextSize;
 
 use crate::test_db::TestDB;
 
 fn check_diagnostics(ra_fixture: &str) {
     let db: TestDB = TestDB::with_files(ra_fixture);
-    let annotations = db.extract_annotations();
-    assert!(!annotations.is_empty());
-
-    let mut actual: FxHashMap<FileId, Vec<(TextRange, String)>> = FxHashMap::default();
-    db.diagnostics(|d| {
-        let src = d.display_source();
-        let root = db.parse_or_expand(src.file_id).unwrap();
-        // FIXME: macros...
-        let file_id = src.file_id.original_file(&db);
-        let range = src.value.to_node(&root).text_range();
-        let message = d.message().to_owned();
-        actual.entry(file_id).or_default().push((range, message));
-    });
-
-    for (file_id, diags) in actual.iter_mut() {
-        diags.sort_by_key(|it| it.0.start());
-        let text = db.file_text(*file_id);
-        // For multiline spans, place them on line start
-        for (range, content) in diags {
-            if text[*range].contains('\n') {
-                *range = TextRange::new(range.start(), range.start() + TextSize::from(1));
-                *content = format!("... {}", content);
-            }
-        }
-    }
-
-    assert_eq!(annotations, actual);
+    db.check_diagnostics();
 }
 
 #[test]
@@ -129,3 +97,25 @@ fn unresolved_module() {
         ",
     );
 }
+
+#[test]
+fn inactive_item() {
+    // Additional tests in `cfg` crate. This only tests disabled cfgs.
+
+    check_diagnostics(
+        r#"
+        //- /lib.rs
+          #[cfg(no)] pub fn f() {}
+        //^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: no is disabled
+
+          #[cfg(no)] #[cfg(no2)] mod m;
+        //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: no and no2 are disabled
+
+          #[cfg(all(not(a), b))] enum E {}
+        //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: b is disabled
+
+          #[cfg(feature = "std")] use std;
+        //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: feature = "std" is disabled
+        "#,
+    );
+}
diff --git a/crates/hir_def/src/test_db.rs b/crates/hir_def/src/test_db.rs
index fb1d3c974..2b36c824a 100644
--- a/crates/hir_def/src/test_db.rs
+++ b/crates/hir_def/src/test_db.rs
@@ -12,10 +12,10 @@ use hir_expand::diagnostics::Diagnostic;
 use hir_expand::diagnostics::DiagnosticSinkBuilder;
 use rustc_hash::FxHashMap;
 use rustc_hash::FxHashSet;
-use syntax::TextRange;
+use syntax::{TextRange, TextSize};
 use test_utils::extract_annotations;
 
-use crate::db::DefDatabase;
+use crate::{db::DefDatabase, ModuleDefId};
 
 #[salsa::database(
     base_db::SourceDatabaseExtStorage,
@@ -135,9 +135,47 @@ impl TestDB {
             let crate_def_map = self.crate_def_map(krate);
 
             let mut sink = DiagnosticSinkBuilder::new().build(&mut cb);
-            for (module_id, _) in crate_def_map.modules.iter() {
+            for (module_id, module) in crate_def_map.modules.iter() {
                 crate_def_map.add_diagnostics(self, module_id, &mut sink);
+
+                for decl in module.scope.declarations() {
+                    if let ModuleDefId::FunctionId(it) = decl {
+                        let source_map = self.body_with_source_map(it.into()).1;
+                        source_map.add_diagnostics(self, &mut sink);
+                    }
+                }
             }
         }
     }
+
+    pub fn check_diagnostics(&self) {
+        let db: &TestDB = self;
+        let annotations = db.extract_annotations();
+        assert!(!annotations.is_empty());
+
+        let mut actual: FxHashMap<FileId, Vec<(TextRange, String)>> = FxHashMap::default();
+        db.diagnostics(|d| {
+            let src = d.display_source();
+            let root = db.parse_or_expand(src.file_id).unwrap();
+            // FIXME: macros...
+            let file_id = src.file_id.original_file(db);
+            let range = src.value.to_node(&root).text_range();
+            let message = d.message().to_owned();
+            actual.entry(file_id).or_default().push((range, message));
+        });
+
+        for (file_id, diags) in actual.iter_mut() {
+            diags.sort_by_key(|it| it.0.start());
+            let text = db.file_text(*file_id);
+            // For multiline spans, place them on line start
+            for (range, content) in diags {
+                if text[*range].contains('\n') {
+                    *range = TextRange::new(range.start(), range.start() + TextSize::from(1));
+                    *content = format!("... {}", content);
+                }
+            }
+        }
+
+        assert_eq!(annotations, actual);
+    }
 }