13 files changed, 389 insertions, 86 deletions

diff --git a/crates/ra_assists/src/assists/apply_demorgan.rs b/crates/ra_assists/src/assists/apply_demorgan.rs
index 068da1774..7c57c0560 100644
--- a/crates/ra_assists/src/assists/apply_demorgan.rs
+++ b/crates/ra_assists/src/assists/apply_demorgan.rs
@@ -1,6 +1,6 @@
+use super::invert_if::invert_boolean_expression;
 use hir::db::HirDatabase;
 use ra_syntax::ast::{self, AstNode};
-use ra_syntax::SyntaxNode;
 
 use crate::{Assist, AssistCtx, AssistId};
 
@@ -32,18 +32,18 @@ pub(crate) fn apply_demorgan(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist>
     if !cursor_in_range {
         return None;
     }
-    let lhs = expr.lhs()?.syntax().clone();
-    let lhs_range = lhs.text_range();
-    let rhs = expr.rhs()?.syntax().clone();
-    let rhs_range = rhs.text_range();
-    let not_lhs = undo_negation(lhs)?;
-    let not_rhs = undo_negation(rhs)?;
+    let lhs = expr.lhs()?;
+    let lhs_range = lhs.syntax().text_range();
+    let rhs = expr.rhs()?;
+    let rhs_range = rhs.syntax().text_range();
+    let not_lhs = invert_boolean_expression(&lhs)?;
+    let not_rhs = invert_boolean_expression(&rhs)?;
 
     ctx.add_assist(AssistId("apply_demorgan"), "apply demorgan's law", |edit| {
         edit.target(op_range);
         edit.replace(op_range, opposite_op);
-        edit.replace(lhs_range, format!("!({}", not_lhs));
-        edit.replace(rhs_range, format!("{})", not_rhs));
+        edit.replace(lhs_range, format!("!({}", not_lhs.syntax().text()));
+        edit.replace(rhs_range, format!("{})", not_rhs.syntax().text()));
     })
 }
 
@@ -56,28 +56,6 @@ fn opposite_logic_op(kind: ast::BinOp) -> Option<&'static str> {
     }
 }
 
-// This function tries to undo unary negation, or inequality
-fn undo_negation(node: SyntaxNode) -> Option<String> {
-    match ast::Expr::cast(node)? {
-        ast::Expr::BinExpr(bin) => match bin.op_kind()? {
-            ast::BinOp::NegatedEqualityTest => {
-                let lhs = bin.lhs()?.syntax().text();
-                let rhs = bin.rhs()?.syntax().text();
-                Some(format!("{} == {}", lhs, rhs))
-            }
-            _ => None,
-        },
-        ast::Expr::PrefixExpr(pe) => match pe.op_kind()? {
-            ast::PrefixOp::Not => {
-                let child = pe.expr()?.syntax().text();
-                Some(String::from(child))
-            }
-            _ => None,
-        },
-        _ => None,
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/crates/ra_assists/src/assists/invert_if.rs b/crates/ra_assists/src/assists/invert_if.rs
new file mode 100644
index 000000000..bababa3e2
--- /dev/null
+++ b/crates/ra_assists/src/assists/invert_if.rs
@@ -0,0 +1,102 @@
+use hir::db::HirDatabase;
+use ra_syntax::ast::{self, AstNode};
+use ra_syntax::T;
+
+use crate::{Assist, AssistCtx, AssistId};
+
+// Assist: invert_if
+//
+// Apply invert_if
+// This transforms if expressions of the form `if !x {A} else {B}` into `if x {B} else {A}`
+// This also works with `!=`. This assist can only be applied with the cursor
+// on `if`.
+//
+// ```
+// fn main() {
+//     if<|> !y { A } else { B }
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     if y { B } else { A }
+// }
+// ```
+
+pub(crate) fn invert_if(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+    let if_keyword = ctx.find_token_at_offset(T![if])?;
+    let expr = ast::IfExpr::cast(if_keyword.parent())?;
+    let if_range = if_keyword.text_range();
+    let cursor_in_range = ctx.frange.range.is_subrange(&if_range);
+    if !cursor_in_range {
+        return None;
+    }
+
+    let cond = expr.condition()?.expr()?;
+    let then_node = expr.then_branch()?.syntax().clone();
+
+    if let ast::ElseBranch::Block(else_block) = expr.else_branch()? {
+        let flip_cond = invert_boolean_expression(&cond)?;
+        let cond_range = cond.syntax().text_range();
+        let else_node = else_block.syntax();
+        let else_range = else_node.text_range();
+        let then_range = then_node.text_range();
+        return ctx.add_assist(AssistId("invert_if"), "invert if branches", |edit| {
+            edit.target(if_range);
+            edit.replace(cond_range, flip_cond.syntax().text());
+            edit.replace(else_range, then_node.text());
+            edit.replace(then_range, else_node.text());
+        });
+    }
+
+    None
+}
+
+pub(crate) fn invert_boolean_expression(expr: &ast::Expr) -> Option<ast::Expr> {
+    match expr {
+        ast::Expr::BinExpr(bin) => match bin.op_kind()? {
+            ast::BinOp::NegatedEqualityTest => bin.replace_op(T![==]).map(|it| it.into()),
+            _ => None,
+        },
+        ast::Expr::PrefixExpr(pe) => match pe.op_kind()? {
+            ast::PrefixOp::Not => pe.expr(),
+            _ => None,
+        },
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn invert_if_remove_inequality() {
+        check_assist(
+            invert_if,
+            "fn f() { i<|>f x != 3 { 1 } else { 3 + 2 } }",
+            "fn f() { i<|>f x == 3 { 3 + 2 } else { 1 } }",
+        )
+    }
+
+    #[test]
+    fn invert_if_remove_not() {
+        check_assist(
+            invert_if,
+            "fn f() { <|>if !cond { 3 * 2 } else { 1 } }",
+            "fn f() { <|>if cond { 1 } else { 3 * 2 } }",
+        )
+    }
+
+    #[test]
+    fn invert_if_doesnt_apply_with_cursor_not_on_if() {
+        check_assist_not_applicable(invert_if, "fn f() { if !<|>cond { 3 * 2 } else { 1 } }")
+    }
+
+    #[test]
+    fn invert_if_doesnt_apply_without_negated() {
+        check_assist_not_applicable(invert_if, "fn f() { i<|>f cond { 3 * 2 } else { 1 } }")
+    }
+}
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index 176761efb..3c716c2d1 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -342,6 +342,23 @@ fn main() {
 }
 
 #[test]
+fn doctest_invert_if() {
+    check(
+        "invert_if",
+        r#####"
+fn main() {
+    if<|> !y { A } else { B }
+}
+"#####,
+        r#####"
+fn main() {
+    if y { B } else { A }
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_make_raw_string() {
     check(
         "make_raw_string",
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index f2f0dacbf..a372bd8b9 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -97,6 +97,7 @@ mod assists {
     mod add_impl;
     mod add_new;
     mod apply_demorgan;
+    mod invert_if;
     mod flip_comma;
     mod flip_binexpr;
     mod flip_trait_bound;
@@ -122,6 +123,7 @@ mod assists {
             add_impl::add_impl,
             add_new::add_new,
             apply_demorgan::apply_demorgan,
+            invert_if::invert_if,
             change_visibility::change_visibility,
             fill_match_arms::fill_match_arms,
             merge_match_arms::merge_match_arms,
diff --git a/crates/ra_hir_expand/src/builtin_macro.rs b/crates/ra_hir_expand/src/builtin_macro.rs
index 4da56529d..c0e0436c0 100644
--- a/crates/ra_hir_expand/src/builtin_macro.rs
+++ b/crates/ra_hir_expand/src/builtin_macro.rs
@@ -8,47 +8,47 @@ use crate::{
 
 use crate::quote;
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub enum BuiltinExpander {
-    Column,
-    File,
-    Line,
-    Stringify,
-}
+macro_rules! register_builtin {
+    ( $(($name:ident, $kind: ident) => $expand:ident),* ) => {
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+        pub enum BuiltinFnLikeExpander {
+            $($kind),*
+        }
 
-impl BuiltinExpander {
-    pub fn expand(
-        &self,
-        db: &dyn AstDatabase,
-        id: MacroCallId,
-        tt: &tt::Subtree,
-    ) -> Result<tt::Subtree, mbe::ExpandError> {
-        match self {
-            BuiltinExpander::Column => column_expand(db, id, tt),
-            BuiltinExpander::File => file_expand(db, id, tt),
-            BuiltinExpander::Line => line_expand(db, id, tt),
-            BuiltinExpander::Stringify => stringify_expand(db, id, tt),
+        impl BuiltinFnLikeExpander {
+            pub fn expand(
+                &self,
+                db: &dyn AstDatabase,
+                id: MacroCallId,
+                tt: &tt::Subtree,
+            ) -> Result<tt::Subtree, mbe::ExpandError> {
+                let expander = match *self {
+                    $( BuiltinFnLikeExpander::$kind => $expand, )*
+                };
+                expander(db, id, tt)
+            }
         }
-    }
+
+        pub fn find_builtin_macro(
+            ident: &name::Name,
+            krate: CrateId,
+            ast_id: AstId<ast::MacroCall>,
+        ) -> Option<MacroDefId> {
+            let kind = match ident {
+                 $( id if id == &name::$name => BuiltinFnLikeExpander::$kind, )*
+                 _ => return None,
+            };
+
+            Some(MacroDefId { krate, ast_id, kind: MacroDefKind::BuiltIn(kind) })
+        }
+    };
 }
 
-pub fn find_builtin_macro(
-    ident: &name::Name,
-    krate: CrateId,
-    ast_id: AstId<ast::MacroCall>,
-) -> Option<MacroDefId> {
-    // FIXME: Better registering method
-    if ident == &name::COLUMN_MACRO {
-        Some(MacroDefId { krate, ast_id, kind: MacroDefKind::BuiltIn(BuiltinExpander::Column) })
-    } else if ident == &name::FILE_MACRO {
-        Some(MacroDefId { krate, ast_id, kind: MacroDefKind::BuiltIn(BuiltinExpander::File) })
-    } else if ident == &name::LINE_MACRO {
-        Some(MacroDefId { krate, ast_id, kind: MacroDefKind::BuiltIn(BuiltinExpander::Line) })
-    } else if ident == &name::STRINGIFY_MACRO {
-        Some(MacroDefId { krate, ast_id, kind: MacroDefKind::BuiltIn(BuiltinExpander::Stringify) })
-    } else {
-        None
-    }
+register_builtin! {
+    (COLUMN_MACRO, Column) => column_expand,
+    (FILE_MACRO, File) => file_expand,
+    (LINE_MACRO, Line) => line_expand,
+    (STRINGIFY_MACRO, Stringify) => stringify_expand
 }
 
 fn to_line_number(db: &dyn AstDatabase, file: HirFileId, pos: TextUnit) -> usize {
@@ -171,3 +171,92 @@ fn file_expand(
 
     Ok(expanded)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{test_db::TestDB, MacroCallLoc};
+    use ra_db::{fixture::WithFixture, SourceDatabase};
+
+    fn expand_builtin_macro(s: &str, expander: BuiltinFnLikeExpander) -> String {
+        let (db, file_id) = TestDB::with_single_file(&s);
+        let parsed = db.parse(file_id);
+        let macro_calls: Vec<_> =
+            parsed.syntax_node().descendants().filter_map(|it| ast::MacroCall::cast(it)).collect();
+
+        let ast_id_map = db.ast_id_map(file_id.into());
+
+        // the first one should be a macro_rules
+        let def = MacroDefId {
+            krate: CrateId(0),
+            ast_id: AstId::new(file_id.into(), ast_id_map.ast_id(&macro_calls[0])),
+            kind: MacroDefKind::BuiltIn(expander),
+        };
+
+        let loc = MacroCallLoc {
+            def,
+            ast_id: AstId::new(file_id.into(), ast_id_map.ast_id(&macro_calls[1])),
+        };
+
+        let id = db.intern_macro(loc);
+        let parsed = db.parse_or_expand(id.as_file(MacroFileKind::Expr)).unwrap();
+
+        parsed.text().to_string()
+    }
+
+    #[test]
+    fn test_column_expand() {
+        let expanded = expand_builtin_macro(
+            r#"
+        #[rustc_builtin_macro]
+        macro_rules! column {() => {}}
+        column!()
+"#,
+            BuiltinFnLikeExpander::Column,
+        );
+
+        assert_eq!(expanded, "9");
+    }
+
+    #[test]
+    fn test_line_expand() {
+        let expanded = expand_builtin_macro(
+            r#"
+        #[rustc_builtin_macro]
+        macro_rules! line {() => {}}
+        line!()
+"#,
+            BuiltinFnLikeExpander::Line,
+        );
+
+        assert_eq!(expanded, "4");
+    }
+
+    #[test]
+    fn test_stringify_expand() {
+        let expanded = expand_builtin_macro(
+            r#"
+        #[rustc_builtin_macro]
+        macro_rules! stringify {() => {}}
+        stringify!(a b c)
+"#,
+            BuiltinFnLikeExpander::Stringify,
+        );
+
+        assert_eq!(expanded, "\"a b c\"");
+    }
+
+    #[test]
+    fn test_file_expand() {
+        let expanded = expand_builtin_macro(
+            r#"
+        #[rustc_builtin_macro]
+        macro_rules! file {() => {}}
+        file!()
+"#,
+            BuiltinFnLikeExpander::File,
+        );
+
+        assert_eq!(expanded, "\"\"");
+    }
+}
diff --git a/crates/ra_hir_expand/src/db.rs b/crates/ra_hir_expand/src/db.rs
index e1d93a8ef..8e46fa177 100644
--- a/crates/ra_hir_expand/src/db.rs
+++ b/crates/ra_hir_expand/src/db.rs
@@ -9,14 +9,14 @@ use ra_prof::profile;
 use ra_syntax::{AstNode, Parse, SyntaxNode};
 
 use crate::{
-    ast_id_map::AstIdMap, BuiltinExpander, HirFileId, HirFileIdRepr, MacroCallId, MacroCallLoc,
-    MacroDefId, MacroDefKind, MacroFile, MacroFileKind,
+    ast_id_map::AstIdMap, BuiltinFnLikeExpander, HirFileId, HirFileIdRepr, MacroCallId,
+    MacroCallLoc, MacroDefId, MacroDefKind, MacroFile, MacroFileKind,
 };
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum TokenExpander {
     MacroRules(mbe::MacroRules),
-    Builtin(BuiltinExpander),
+    Builtin(BuiltinFnLikeExpander),
 }
 
 impl TokenExpander {
diff --git a/crates/ra_hir_expand/src/lib.rs b/crates/ra_hir_expand/src/lib.rs
index 126d12fbb..4f3ccf1d0 100644
--- a/crates/ra_hir_expand/src/lib.rs
+++ b/crates/ra_hir_expand/src/lib.rs
@@ -24,7 +24,10 @@ use ra_syntax::{
 };
 
 use crate::ast_id_map::FileAstId;
-use crate::builtin_macro::BuiltinExpander;
+use crate::builtin_macro::BuiltinFnLikeExpander;
+
+#[cfg(test)]
+mod test_db;
 
 /// Input to the analyzer is a set of files, where each file is identified by
 /// `FileId` and contains source code. However, another source of source code in
@@ -135,7 +138,7 @@ pub struct MacroDefId {
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum MacroDefKind {
     Declarative,
-    BuiltIn(BuiltinExpander),
+    BuiltIn(BuiltinFnLikeExpander),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
diff --git a/crates/ra_hir_expand/src/test_db.rs b/crates/ra_hir_expand/src/test_db.rs
new file mode 100644
index 000000000..d23e75d9e
--- /dev/null
+++ b/crates/ra_hir_expand/src/test_db.rs
@@ -0,0 +1,50 @@
+//! Database used for testing `hir_expand`.
+
+use std::{
+    panic,
+    sync::{Arc, Mutex},
+};
+
+use ra_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, RelativePath};
+
+#[salsa::database(
+    ra_db::SourceDatabaseExtStorage,
+    ra_db::SourceDatabaseStorage,
+    crate::db::AstDatabaseStorage
+)]
+#[derive(Debug, Default)]
+pub struct TestDB {
+    runtime: salsa::Runtime<TestDB>,
+    events: Mutex<Option<Vec<salsa::Event<TestDB>>>>,
+}
+
+impl salsa::Database for TestDB {
+    fn salsa_runtime(&self) -> &salsa::Runtime<Self> {
+        &self.runtime
+    }
+
+    fn salsa_event(&self, event: impl Fn() -> salsa::Event<TestDB>) {
+        let mut events = self.events.lock().unwrap();
+        if let Some(events) = &mut *events {
+            events.push(event());
+        }
+    }
+}
+
+impl panic::RefUnwindSafe for TestDB {}
+
+impl FileLoader for TestDB {
+    fn file_text(&self, file_id: FileId) -> Arc<String> {
+        FileLoaderDelegate(self).file_text(file_id)
+    }
+    fn resolve_relative_path(
+        &self,
+        anchor: FileId,
+        relative_path: &RelativePath,
+    ) -> Option<FileId> {
+        FileLoaderDelegate(self).resolve_relative_path(anchor, relative_path)
+    }
+    fn relevant_crates(&self, file_id: FileId) -> Arc<Vec<CrateId>> {
+        FileLoaderDelegate(self).relevant_crates(file_id)
+    }
+}
diff --git a/crates/ra_ide_api/src/expand_macro.rs b/crates/ra_ide_api/src/expand_macro.rs
index 673301b10..0b540b8cd 100644
--- a/crates/ra_ide_api/src/expand_macro.rs
+++ b/crates/ra_ide_api/src/expand_macro.rs
@@ -47,15 +47,15 @@ fn expand_macro_recur(
 
     for child in children.into_iter() {
         let node = hir::Source::new(macro_file_id, &child);
-        let new_node = expand_macro_recur(db, source, node)?;
-
-        // Replace the whole node if it is root
-        // `replace_descendants` will not replace the parent node
-        // but `SyntaxNode::descendants include itself
-        if expanded == *child.syntax() {
-            expanded = new_node;
-        } else {
-            replaces.insert(child.syntax().clone().into(), new_node.into());
+        if let Some(new_node) = expand_macro_recur(db, source, node) {
+            // Replace the whole node if it is root
+            // `replace_descendants` will not replace the parent node
+            // but `SyntaxNode::descendants include itself
+            if expanded == *child.syntax() {
+                expanded = new_node;
+            } else {
+                replaces.insert(child.syntax().clone().into(), new_node.into());
+            }
         }
     }
 
@@ -247,4 +247,26 @@ fn some_thing() -> u32 {
         assert_eq!(res.name, "match_ast");
         assert_snapshot!(res.expansion, @r###"{}"###);
     }
+
+    #[test]
+    fn macro_expand_inner_macro_fail_to_expand() {
+        let res = check_expand_macro(
+            r#"
+        //- /lib.rs
+        macro_rules! bar {
+            (BAD) => {};
+        }
+        macro_rules! foo {
+            () => {bar!()};
+        }        
+
+        fn main() {        
+            let res = fo<|>o!();
+        }
+        "#,
+        );
+
+        assert_eq!(res.name, "foo");
+        assert_snapshot!(res.expansion, @r###"bar!()"###);
+    }
 }
diff --git a/crates/ra_syntax/src/ast/edit.rs b/crates/ra_syntax/src/ast/edit.rs
index 6f005a2d8..95bf9db14 100644
--- a/crates/ra_syntax/src/ast/edit.rs
+++ b/crates/ra_syntax/src/ast/edit.rs
@@ -13,11 +13,21 @@ use crate::{
         make::{self, tokens},
         AstNode, TypeBoundsOwner,
     },
-    AstToken, Direction, InsertPosition, SmolStr, SyntaxElement,
+    AstToken, Direction, InsertPosition, SmolStr, SyntaxElement, SyntaxKind,
     SyntaxKind::{ATTR, COMMENT, WHITESPACE},
     SyntaxNode, SyntaxToken, T,
 };
 
+impl ast::BinExpr {
+    #[must_use]
+    pub fn replace_op(&self, op: SyntaxKind) -> Option<ast::BinExpr> {
+        let op_node: SyntaxElement = self.op_details()?.0.into();
+        let to_insert: Option<SyntaxElement> = Some(tokens::op(op).into());
+        let replace_range = RangeInclusive::new(op_node.clone(), op_node);
+        Some(replace_children(self, replace_range, to_insert.into_iter()))
+    }
+}
+
 impl ast::FnDef {
     #[must_use]
     pub fn with_body(&self, body: ast::Block) -> ast::FnDef {
diff --git a/crates/ra_syntax/src/ast/expr_extensions.rs b/crates/ra_syntax/src/ast/expr_extensions.rs
index 7c53aa934..2fd039837 100644
--- a/crates/ra_syntax/src/ast/expr_extensions.rs
+++ b/crates/ra_syntax/src/ast/expr_extensions.rs
@@ -127,7 +127,7 @@ pub enum BinOp {
 }
 
 impl ast::BinExpr {
-    fn op_details(&self) -> Option<(SyntaxToken, BinOp)> {
+    pub fn op_details(&self) -> Option<(SyntaxToken, BinOp)> {
         self.syntax().children_with_tokens().filter_map(|it| it.into_token()).find_map(|c| {
             let bin_op = match c.kind() {
                 T![||] => BinOp::BooleanOr,
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index 9749327fa..40db570da 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -173,10 +173,21 @@ fn ast_from_text<N: AstNode>(text: &str) -> N {
 }
 
 pub mod tokens {
-    use crate::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
+    use crate::{AstNode, Parse, SourceFile, SyntaxKind, SyntaxKind::*, SyntaxToken, T};
     use once_cell::sync::Lazy;
 
-    static SOURCE_FILE: Lazy<Parse<SourceFile>> = Lazy::new(|| SourceFile::parse(",\n; ;"));
+    static SOURCE_FILE: Lazy<Parse<SourceFile>> =
+        Lazy::new(|| SourceFile::parse("const C: () = (1 != 1, 2 == 2)\n;"));
+
+    pub fn op(op: SyntaxKind) -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == op)
+            .unwrap()
+    }
 
     pub fn comma() -> SyntaxToken {
         SOURCE_FILE
diff --git a/docs/user/assists.md b/docs/user/assists.md
index 8da7578e2..6f4c30bee 100644
--- a/docs/user/assists.md
+++ b/docs/user/assists.md
@@ -329,6 +329,25 @@ fn main() {
 }
 ```
 
+## `invert_if`
+
+Apply invert_if
+This transforms if expressions of the form `if !x {A} else {B}` into `if x {B} else {A}`
+This also works with `!=`. This assist can only be applied with the cursor
+on `if`.
+
+```rust
+// BEFORE
+fn main() {
+    if┃ !y { A } else { B }
+}
+
+// AFTER
+fn main() {
+    if y { B } else { A }
+}
+```
+
 ## `make_raw_string`
 
 Adds `r#` to a plain string literal.