2 files changed, 300 insertions, 0 deletions

diff --git a/crates/ra_assists/src/inline_local_variable.rs b/crates/ra_assists/src/inline_local_variable.rs
new file mode 100644
index 000000000..bd3cdb970
--- /dev/null
+++ b/crates/ra_assists/src/inline_local_variable.rs
@@ -0,0 +1,298 @@
+use hir::db::HirDatabase;
+use hir::source_binder::function_from_child_node;
+use ra_syntax::{ast::{self, AstNode}, TextRange};
+use ra_syntax::ast::{PatKind, ExprKind};
+
+use crate::{Assist, AssistCtx, AssistId};
+use crate::assist_ctx::AssistBuilder;
+
+pub(crate) fn inline_local_varialbe(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+    let let_stmt = ctx.node_at_offset::<ast::LetStmt>()?;
+    let bind_pat = match let_stmt.pat()?.kind() {
+        PatKind::BindPat(pat) => pat,
+        _ => return None,
+    };
+    if bind_pat.is_mutable() {
+        return None;
+    }
+    let initializer = let_stmt.initializer()?;
+    let wrap_in_parens = match initializer.kind() {
+        ExprKind::LambdaExpr(_)
+        | ExprKind::IfExpr(_)
+        | ExprKind::LoopExpr(_)
+        | ExprKind::ForExpr(_)
+        | ExprKind::WhileExpr(_)
+        | ExprKind::ContinueExpr(_)
+        | ExprKind::BreakExpr(_)
+        | ExprKind::Label(_)
+        | ExprKind::ReturnExpr(_)
+        | ExprKind::MatchExpr(_)
+        | ExprKind::StructLit(_)
+        | ExprKind::CastExpr(_)
+        | ExprKind::PrefixExpr(_)
+        | ExprKind::RangeExpr(_)
+        | ExprKind::BinExpr(_) => true,
+        ExprKind::CallExpr(_)
+        | ExprKind::IndexExpr(_)
+        | ExprKind::MethodCallExpr(_)
+        | ExprKind::FieldExpr(_)
+        | ExprKind::TryExpr(_)
+        | ExprKind::RefExpr(_)
+        | ExprKind::Literal(_)
+        | ExprKind::TupleExpr(_)
+        | ExprKind::ArrayExpr(_)
+        | ExprKind::ParenExpr(_)
+        | ExprKind::PathExpr(_)
+        | ExprKind::BlockExpr(_) => false,
+    };
+
+    let delete_range = if let Some(whitespace) =
+        let_stmt.syntax().next_sibling().and_then(ast::Whitespace::cast)
+    {
+        TextRange::from_to(let_stmt.syntax().range().start(), whitespace.syntax().range().end())
+    } else {
+        let_stmt.syntax().range()
+    };
+
+    let init_str = if wrap_in_parens {
+        format!("({})", initializer.syntax().text().to_string())
+    } else {
+        initializer.syntax().text().to_string()
+    };
+    let function = function_from_child_node(ctx.db, ctx.frange.file_id, bind_pat.syntax())?;
+    let scope = function.scopes(ctx.db);
+    let refs = scope.find_all_refs(bind_pat);
+
+    ctx.add_action(
+        AssistId("inline_local_variable"),
+        "inline local variable",
+        move |edit: &mut AssistBuilder| {
+            edit.delete(delete_range);
+            for desc in refs {
+                edit.replace(desc.range, init_str.clone())
+            }
+            edit.set_cursor(delete_range.start())
+        },
+    );
+
+    ctx.build()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn test_inline_let_bind_literal_expr() {
+        check_assist(
+            inline_local_varialbe,
+            "
+fn bar(a: usize) {}
+fn foo() {
+    let a<|> = 1;
+    a + 1;
+    if a > 10 {
+    }
+
+    while a > 10 {
+
+    }
+    let b = a * 10;
+    bar(a);
+}",
+            "
+fn bar(a: usize) {}
+fn foo() {
+    <|>1 + 1;
+    if 1 > 10 {
+    }
+
+    while 1 > 10 {
+
+    }
+    let b = 1 * 10;
+    bar(1);
+}",
+        );
+    }
+
+    #[test]
+    fn test_inline_let_bind_bin_expr() {
+        check_assist(
+            inline_local_varialbe,
+            "
+fn bar(a: usize) {}
+fn foo() {
+    let a<|> = 1 + 1;
+    a + 1;
+    if a > 10 {
+    }
+
+    while a > 10 {
+
+    }
+    let b = a * 10;
+    bar(a);
+}",
+            "
+fn bar(a: usize) {}
+fn foo() {
+    <|>(1 + 1) + 1;
+    if (1 + 1) > 10 {
+    }
+
+    while (1 + 1) > 10 {
+
+    }
+    let b = (1 + 1) * 10;
+    bar((1 + 1));
+}",
+        );
+    }
+
+    #[test]
+    fn test_inline_let_bind_function_call_expr() {
+        check_assist(
+            inline_local_varialbe,
+            "
+fn bar(a: usize) {}
+fn foo() {
+    let a<|> = bar(1);
+    a + 1;
+    if a > 10 {
+    }
+
+    while a > 10 {
+
+    }
+    let b = a * 10;
+    bar(a);
+}",
+            "
+fn bar(a: usize) {}
+fn foo() {
+    <|>bar(1) + 1;
+    if bar(1) > 10 {
+    }
+
+    while bar(1) > 10 {
+
+    }
+    let b = bar(1) * 10;
+    bar(bar(1));
+}",
+        );
+    }
+
+    #[test]
+    fn test_inline_let_bind_cast_expr() {
+        check_assist(
+            inline_local_varialbe,
+            "
+fn bar(a: usize): usize { a }
+fn foo() {
+    let a<|> = bar(1) as u64;
+    a + 1;
+    if a > 10 {
+    }
+
+    while a > 10 {
+
+    }
+    let b = a * 10;
+    bar(a);
+}",
+            "
+fn bar(a: usize): usize { a }
+fn foo() {
+    <|>(bar(1) as u64) + 1;
+    if (bar(1) as u64) > 10 {
+    }
+
+    while (bar(1) as u64) > 10 {
+
+    }
+    let b = (bar(1) as u64) * 10;
+    bar((bar(1) as u64));
+}",
+        );
+    }
+
+    #[test]
+    fn test_inline_let_bind_block_expr() {
+        check_assist(
+            inline_local_varialbe,
+            "
+fn foo() {
+    let a<|> = { 10 + 1 };
+    a + 1;
+    if a > 10 {
+    }
+
+    while a > 10 {
+
+    }
+    let b = a * 10;
+    bar(a);
+}",
+            "
+fn foo() {
+    <|>{ 10 + 1 } + 1;
+    if { 10 + 1 } > 10 {
+    }
+
+    while { 10 + 1 } > 10 {
+
+    }
+    let b = { 10 + 1 } * 10;
+    bar({ 10 + 1 });
+}",
+        );
+    }
+
+    #[test]
+    fn test_inline_let_bind_paren_expr() {
+        check_assist(
+            inline_local_varialbe,
+            "
+fn foo() {
+    let a<|> = ( 10 + 1 );
+    a + 1;
+    if a > 10 {
+    }
+
+    while a > 10 {
+
+    }
+    let b = a * 10;
+    bar(a);
+}",
+            "
+fn foo() {
+    <|>( 10 + 1 ) + 1;
+    if ( 10 + 1 ) > 10 {
+    }
+
+    while ( 10 + 1 ) > 10 {
+
+    }
+    let b = ( 10 + 1 ) * 10;
+    bar(( 10 + 1 ));
+}",
+        );
+    }
+
+    #[test]
+    fn test_not_inline_mut_variable() {
+        check_assist_not_applicable(
+            inline_local_varialbe,
+            "
+fn foo() {
+    let mut a<|> = 1 + 1;
+    a + 1;
+}",
+        );
+    }
+}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index 8900fbc4b..2e47b5215 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -93,6 +93,7 @@ mod change_visibility;
 mod fill_match_arms;
 mod fill_struct_fields;
 mod introduce_variable;
+mod inline_local_variable;
 mod replace_if_let_with_match;
 mod split_import;
 mod remove_dbg;
@@ -115,6 +116,7 @@ fn all_assists<DB: HirDatabase>() -> &'static [fn(AssistCtx<DB>) -> Option<Assis
         auto_import::auto_import,
         add_missing_impl_members::add_missing_impl_members,
         add_missing_impl_members::add_missing_default_members,
+        inline_local_variable::inline_local_varialbe,
     ]
 }