4 files changed, 609 insertions, 14 deletions

diff --git a/crates/ide_assists/src/handlers/add_turbo_fish.rs b/crates/ide_assists/src/handlers/add_turbo_fish.rs
index 3b6efbab4..ee879c151 100644
--- a/crates/ide_assists/src/handlers/add_turbo_fish.rs
+++ b/crates/ide_assists/src/handlers/add_turbo_fish.rs
@@ -56,13 +56,20 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext) -> Option<(
     if let Some(let_stmt) = ctx.find_node_at_offset::<ast::LetStmt>() {
         if let_stmt.colon_token().is_none() {
             let type_pos = let_stmt.pat()?.syntax().last_token()?.text_range().end();
+            let semi_pos = let_stmt.syntax().last_token()?.text_range().end();
+
             acc.add(
                 AssistId("add_type_ascription", AssistKind::RefactorRewrite),
                 "Add `: _` before assignment operator",
                 ident.text_range(),
-                |builder| match ctx.config.snippet_cap {
-                    Some(cap) => builder.insert_snippet(cap, type_pos, ": ${0:_}"),
-                    None => builder.insert(type_pos, ": _"),
+                |builder| {
+                    if let_stmt.semicolon_token().is_none() {
+                        builder.insert(semi_pos, ";");
+                    }
+                    match ctx.config.snippet_cap {
+                        Some(cap) => builder.insert_snippet(cap, type_pos, ": ${0:_}"),
+                        None => builder.insert(type_pos, ": _"),
+                    }
                 },
             )?
         } else {
@@ -265,4 +272,24 @@ fn main() {
 "#,
         );
     }
+
+    #[test]
+    fn add_type_ascription_append_semicolon() {
+        check_assist_by_label(
+            add_turbo_fish,
+            r#"
+fn make<T>() -> T {}
+fn main() {
+    let x = make$0()
+}
+"#,
+            r#"
+fn make<T>() -> T {}
+fn main() {
+    let x: ${0:_} = make();
+}
+"#,
+            "Add `: _` before assignment operator",
+        );
+    }
 }
diff --git a/crates/ide_assists/src/handlers/apply_demorgan.rs b/crates/ide_assists/src/handlers/apply_demorgan.rs
index a1c339603..5c936a510 100644
--- a/crates/ide_assists/src/handlers/apply_demorgan.rs
+++ b/crates/ide_assists/src/handlers/apply_demorgan.rs
@@ -1,3 +1,5 @@
+use std::collections::VecDeque;
+
 use syntax::ast::{self, AstNode};
 
 use crate::{utils::invert_boolean_expression, AssistContext, AssistId, AssistKind, Assists};
@@ -30,19 +32,52 @@ pub(crate) fn apply_demorgan(acc: &mut Assists, ctx: &AssistContext) -> Option<(
         return None;
     }
 
-    let lhs = expr.lhs()?;
-    let lhs_range = lhs.syntax().text_range();
-    let not_lhs = invert_boolean_expression(&ctx.sema, lhs);
+    let mut expr = expr;
+
+    // Walk up the tree while we have the same binary operator
+    while let Some(parent_expr) = expr.syntax().parent().and_then(ast::BinExpr::cast) {
+        if let Some(parent_op) = expr.op_kind() {
+            if parent_op == op {
+                expr = parent_expr
+            }
+        }
+    }
+
+    let mut expr_stack = vec![expr.clone()];
+    let mut terms = Vec::new();
+    let mut op_ranges = Vec::new();
+
+    // Find all the children with the same binary operator
+    while let Some(expr) = expr_stack.pop() {
+        let mut traverse_bin_expr_arm = |expr| {
+            if let ast::Expr::BinExpr(bin_expr) = expr {
+                if let Some(expr_op) = bin_expr.op_kind() {
+                    if expr_op == op {
+                        expr_stack.push(bin_expr);
+                    } else {
+                        terms.push(ast::Expr::BinExpr(bin_expr));
+                    }
+                } else {
+                    terms.push(ast::Expr::BinExpr(bin_expr));
+                }
+            } else {
+                terms.push(expr);
+            }
+        };
 
-    let rhs = expr.rhs()?;
-    let rhs_range = rhs.syntax().text_range();
-    let not_rhs = invert_boolean_expression(&ctx.sema, rhs);
+        op_ranges.extend(expr.op_token().map(|t| t.text_range()));
+        traverse_bin_expr_arm(expr.lhs()?);
+        traverse_bin_expr_arm(expr.rhs()?);
+    }
 
     acc.add(
         AssistId("apply_demorgan", AssistKind::RefactorRewrite),
         "Apply De Morgan's law",
         op_range,
         |edit| {
+            terms.sort_by_key(|t| t.syntax().text_range().start());
+            let mut terms = VecDeque::from(terms);
+
             let paren_expr = expr.syntax().parent().and_then(|parent| ast::ParenExpr::cast(parent));
 
             let neg_expr = paren_expr
@@ -57,11 +92,18 @@ pub(crate) fn apply_demorgan(acc: &mut Assists, ctx: &AssistContext) -> Option<(
                     }
                 });
 
-            edit.replace(op_range, opposite_op);
+            for op_range in op_ranges {
+                edit.replace(op_range, opposite_op);
+            }
 
             if let Some(paren_expr) = paren_expr {
-                edit.replace(lhs_range, not_lhs.syntax().text());
-                edit.replace(rhs_range, not_rhs.syntax().text());
+                for term in terms {
+                    let range = term.syntax().text_range();
+                    let not_term = invert_boolean_expression(&ctx.sema, term);
+
+                    edit.replace(range, not_term.syntax().text());
+                }
+
                 if let Some(neg_expr) = neg_expr {
                     cov_mark::hit!(demorgan_double_negation);
                     edit.replace(neg_expr.op_token().unwrap().text_range(), "");
@@ -70,8 +112,25 @@ pub(crate) fn apply_demorgan(acc: &mut Assists, ctx: &AssistContext) -> Option<(
                     edit.replace(paren_expr.l_paren_token().unwrap().text_range(), "!(");
                 }
             } else {
-                edit.replace(lhs_range, format!("!({}", not_lhs.syntax().text()));
-                edit.replace(rhs_range, format!("{})", not_rhs.syntax().text()));
+                if let Some(lhs) = terms.pop_front() {
+                    let lhs_range = lhs.syntax().text_range();
+                    let not_lhs = invert_boolean_expression(&ctx.sema, lhs);
+
+                    edit.replace(lhs_range, format!("!({}", not_lhs.syntax().text()));
+                }
+
+                if let Some(rhs) = terms.pop_back() {
+                    let rhs_range = rhs.syntax().text_range();
+                    let not_rhs = invert_boolean_expression(&ctx.sema, rhs);
+
+                    edit.replace(rhs_range, format!("{})", not_rhs.syntax().text()));
+                }
+
+                for term in terms {
+                    let term_range = term.syntax().text_range();
+                    let not_term = invert_boolean_expression(&ctx.sema, term);
+                    edit.replace(term_range, not_term.syntax().text());
+                }
             }
         },
     )
@@ -180,6 +239,12 @@ fn f() {
     }
 
     #[test]
+    fn demorgan_multiple_terms() {
+        check_assist(apply_demorgan, "fn f() { x ||$0 y || z }", "fn f() { !(!x && !y && !z) }");
+        check_assist(apply_demorgan, "fn f() { x || y ||$0 z }", "fn f() { !(!x && !y && !z) }");
+    }
+
+    #[test]
     fn demorgan_doesnt_apply_with_cursor_not_on_op() {
         check_assist_not_applicable(apply_demorgan, "fn f() { $0 !x || !x }")
     }
diff --git a/crates/ide_assists/src/handlers/convert_iter_for_each_to_for.rs b/crates/ide_assists/src/handlers/convert_iter_for_each_to_for.rs
new file mode 100644
index 000000000..4e75a7b14
--- /dev/null
+++ b/crates/ide_assists/src/handlers/convert_iter_for_each_to_for.rs
@@ -0,0 +1,248 @@
+use ide_db::helpers::FamousDefs;
+use syntax::{
+    ast::{self, edit::AstNodeEdit, make, ArgListOwner},
+    AstNode,
+};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: convert_iter_for_each_to_for
+//
+// Converts an Iterator::for_each function into a for loop.
+//
+// ```
+// # //- /lib.rs crate:core
+// # pub mod iter { pub mod traits { pub mod iterator { pub trait Iterator {} } } }
+// # pub struct SomeIter;
+// # impl self::iter::traits::iterator::Iterator for SomeIter {}
+// # //- /lib.rs crate:main deps:core
+// # use core::SomeIter;
+// fn main() {
+//     let iter = SomeIter;
+//     iter.for_each$0(|(x, y)| {
+//         println!("x: {}, y: {}", x, y);
+//     });
+// }
+// ```
+// ->
+// ```
+// # use core::SomeIter;
+// fn main() {
+//     let iter = SomeIter;
+//     for (x, y) in iter {
+//         println!("x: {}, y: {}", x, y);
+//     }
+// }
+// ```
+
+pub(crate) fn convert_iter_for_each_to_for(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let method = ctx.find_node_at_offset::<ast::MethodCallExpr>()?;
+
+    let closure = match method.arg_list()?.args().next()? {
+        ast::Expr::ClosureExpr(expr) => expr,
+        _ => return None,
+    };
+
+    let (method, receiver) = validate_method_call_expr(ctx, method)?;
+
+    let param_list = closure.param_list()?;
+    let param = param_list.params().next()?.pat()?;
+    let body = closure.body()?;
+
+    let stmt = method.syntax().parent().and_then(ast::ExprStmt::cast);
+    let syntax = stmt.as_ref().map_or(method.syntax(), |stmt| stmt.syntax());
+
+    acc.add(
+        AssistId("convert_iter_for_each_to_for", AssistKind::RefactorRewrite),
+        "Replace this `Iterator::for_each` with a for loop",
+        syntax.text_range(),
+        |builder| {
+            let indent = stmt.as_ref().map_or(method.indent_level(), |stmt| stmt.indent_level());
+
+            let block = match body {
+                ast::Expr::BlockExpr(block) => block,
+                _ => make::block_expr(Vec::new(), Some(body)),
+            }
+            .reset_indent()
+            .indent(indent);
+
+            let expr_for_loop = make::expr_for_loop(param, receiver, block);
+            builder.replace(syntax.text_range(), expr_for_loop.syntax().text())
+        },
+    )
+}
+
+fn validate_method_call_expr(
+    ctx: &AssistContext,
+    expr: ast::MethodCallExpr,
+) -> Option<(ast::Expr, ast::Expr)> {
+    let name_ref = expr.name_ref()?;
+    if name_ref.syntax().text_range().intersect(ctx.frange.range).is_none()
+        || name_ref.text() != "for_each"
+    {
+        return None;
+    }
+
+    let sema = &ctx.sema;
+
+    let receiver = expr.receiver()?;
+    let expr = ast::Expr::MethodCallExpr(expr);
+
+    let it_type = sema.type_of_expr(&receiver)?;
+    let module = sema.scope(receiver.syntax()).module()?;
+    let krate = module.krate();
+
+    let iter_trait = FamousDefs(sema, Some(krate)).core_iter_Iterator()?;
+    it_type.impls_trait(sema.db, iter_trait, &[]).then(|| (expr, receiver))
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{self, check_assist};
+
+    use super::*;
+
+    const EMPTY_ITER_FIXTURE: &'static str = r"
+//- /lib.rs deps:core crate:empty_iter
+pub struct EmptyIter;
+impl Iterator for EmptyIter {
+    type Item = usize;
+    fn next(&mut self) -> Option<Self::Item> { None }
+}
+pub struct Empty;
+impl Empty {
+    pub fn iter(&self) -> EmptyIter { EmptyIter }
+}
+";
+
+    fn check_assist_with_fixtures(before: &str, after: &str) {
+        let before = &format!(
+            "//- /main.rs crate:main deps:core,empty_iter{}{}{}",
+            before,
+            EMPTY_ITER_FIXTURE,
+            FamousDefs::FIXTURE,
+        );
+        check_assist(convert_iter_for_each_to_for, before, after);
+    }
+
+    fn check_assist_not_applicable(before: &str) {
+        let before = &format!(
+            "//- /main.rs crate:main deps:core,empty_iter{}{}{}",
+            before,
+            EMPTY_ITER_FIXTURE,
+            FamousDefs::FIXTURE,
+        );
+        tests::check_assist_not_applicable(convert_iter_for_each_to_for, before);
+    }
+
+    #[test]
+    fn test_for_each_in_method_stmt() {
+        check_assist_with_fixtures(
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty;
+    x.iter().$0for_each(|(x, y)| {
+        println!("x: {}, y: {}", x, y);
+    });
+}"#,
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty;
+    for (x, y) in x.iter() {
+        println!("x: {}, y: {}", x, y);
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn test_for_each_in_method() {
+        check_assist_with_fixtures(
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty;
+    x.iter().$0for_each(|(x, y)| {
+        println!("x: {}, y: {}", x, y);
+    })
+}"#,
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty;
+    for (x, y) in x.iter() {
+        println!("x: {}, y: {}", x, y);
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn test_for_each_in_iter_stmt() {
+        check_assist_with_fixtures(
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty.iter();
+    x.$0for_each(|(x, y)| {
+        println!("x: {}, y: {}", x, y);
+    });
+}"#,
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty.iter();
+    for (x, y) in x {
+        println!("x: {}, y: {}", x, y);
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn test_for_each_without_braces_stmt() {
+        check_assist_with_fixtures(
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty;
+    x.iter().$0for_each(|(x, y)| println!("x: {}, y: {}", x, y));
+}"#,
+            r#"
+use empty_iter::*;
+fn main() {
+    let x = Empty;
+    for (x, y) in x.iter() {
+        println!("x: {}, y: {}", x, y)
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn test_for_each_not_applicable() {
+        check_assist_not_applicable(
+            r#"
+fn main() {
+    ().$0for_each(|x| println!("{}", x));
+}"#,
+        )
+    }
+
+    #[test]
+    fn test_for_each_not_applicable_invalid_cursor_pos() {
+        check_assist_not_applicable(
+            r#"
+use empty_iter::*;
+fn main() {
+    Empty.iter().for_each(|(x, y)| $0println!("x: {}, y: {}", x, y));
+}"#,
+        )
+    }
+}
diff --git a/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs b/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
new file mode 100644
index 000000000..aa7072f25
--- /dev/null
+++ b/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
@@ -0,0 +1,255 @@
+use hir::{known, HasSource, Name};
+use syntax::{
+    ast::{self, NameOwner},
+    AstNode, TextRange,
+};
+
+use crate::{
+    assist_context::{AssistContext, Assists},
+    AssistId, AssistKind,
+};
+
+// Assist: generate_is_empty_from_len
+//
+// Generates is_empty implementation from the len method.
+//
+// ```
+// struct MyStruct { data: Vec<String> }
+//
+// impl MyStruct {
+//     p$0ub fn len(&self) -> usize {
+//         self.data.len()
+//     }
+// }
+// ```
+// ->
+// ```
+// struct MyStruct { data: Vec<String> }
+//
+// impl MyStruct {
+//     pub fn len(&self) -> usize {
+//         self.data.len()
+//     }
+//
+//     pub fn is_empty(&self) -> bool {
+//         self.len() == 0
+//     }
+// }
+// ```
+pub(crate) fn generate_is_empty_from_len(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let fn_node = ctx.find_node_at_offset::<ast::Fn>()?;
+    let fn_name = fn_node.name()?;
+
+    if fn_name.text() != "len" {
+        cov_mark::hit!(len_function_not_present);
+        return None;
+    }
+
+    if fn_node.param_list()?.params().next().is_some() {
+        cov_mark::hit!(len_function_with_parameters);
+        return None;
+    }
+
+    let impl_ = fn_node.syntax().ancestors().find_map(ast::Impl::cast)?;
+    if get_impl_method(ctx, &impl_, &known::is_empty).is_some() {
+        cov_mark::hit!(is_empty_already_implemented);
+        return None;
+    }
+
+    let range = get_text_range_of_len_function(ctx, &impl_)?;
+
+    acc.add(
+        AssistId("generate_is_empty_from_len", AssistKind::Generate),
+        "Generate a is_empty impl from a len function",
+        range,
+        |builder| {
+            let code = r#"
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }"#
+            .to_string();
+            builder.insert(range.end(), code)
+        },
+    )
+}
+
+fn get_impl_method(
+    ctx: &AssistContext,
+    impl_: &ast::Impl,
+    fn_name: &Name,
+) -> Option<hir::Function> {
+    let db = ctx.sema.db;
+    let impl_def: hir::Impl = ctx.sema.to_def(impl_)?;
+
+    let scope = ctx.sema.scope(impl_.syntax());
+    let krate = impl_def.module(db).krate();
+    let ty = impl_def.target_ty(db);
+    let traits_in_scope = scope.traits_in_scope();
+    ty.iterate_method_candidates(db, krate, &traits_in_scope, Some(fn_name), |_, func| Some(func))
+}
+
+fn get_text_range_of_len_function(ctx: &AssistContext, impl_: &ast::Impl) -> Option<TextRange> {
+    let db = ctx.sema.db;
+    let func = get_impl_method(ctx, impl_, &known::len)?;
+    let node = func.source(db)?;
+    Some(node.syntax().value.text_range())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn len_function_not_present() {
+        cov_mark::check!(len_function_not_present);
+        check_assist_not_applicable(
+            generate_is_empty_from_len,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    p$0ub fn test(&self) -> usize {
+            self.data.len()
+        }
+    }
+"#,
+        );
+    }
+
+    #[test]
+    fn len_function_with_parameters() {
+        cov_mark::check!(len_function_with_parameters);
+        check_assist_not_applicable(
+            generate_is_empty_from_len,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    p$0ub fn len(&self, _i: bool) -> usize {
+        self.data.len()
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn is_empty_already_implemented() {
+        cov_mark::check!(is_empty_already_implemented);
+        check_assist_not_applicable(
+            generate_is_empty_from_len,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    p$0ub fn len(&self) -> usize {
+        self.data.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn generate_is_empty() {
+        check_assist(
+            generate_is_empty_from_len,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    p$0ub fn len(&self) -> usize {
+        self.data.len()
+    }
+}
+"#,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    pub fn len(&self) -> usize {
+        self.data.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn multiple_functions_in_impl() {
+        check_assist(
+            generate_is_empty_from_len,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    pub fn new() -> Self {
+        Self { data: 0 }
+    }
+
+    p$0ub fn len(&self) -> usize {
+        self.data.len()
+    }
+
+    pub fn work(&self) -> Option<usize> {
+
+    }
+}
+"#,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    pub fn new() -> Self {
+        Self { data: 0 }
+    }
+
+    pub fn len(&self) -> usize {
+        self.data.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    pub fn work(&self) -> Option<usize> {
+
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn multiple_impls() {
+        check_assist_not_applicable(
+            generate_is_empty_from_len,
+            r#"
+struct MyStruct { data: Vec<String> }
+
+impl MyStruct {
+    p$0ub fn len(&self) -> usize {
+        self.data.len()
+    }
+}
+
+impl MyStruct {
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+}
+"#,
+        );
+    }
+}