1 files changed, 313 insertions, 0 deletions

diff --git a/crates/assists/src/utils.rs b/crates/assists/src/utils.rs
new file mode 100644
index 000000000..84ccacafe
--- /dev/null
+++ b/crates/assists/src/utils.rs
@@ -0,0 +1,313 @@
+//! Assorted functions shared by several assists.
+pub(crate) mod insert_use;
+
+use std::{iter, ops};
+
+use hir::{Adt, Crate, Enum, ScopeDef, Semantics, Trait, Type};
+use ide_db::RootDatabase;
+use itertools::Itertools;
+use rustc_hash::FxHashSet;
+use syntax::{
+    ast::{self, make, NameOwner},
+    AstNode,
+    SyntaxKind::*,
+    SyntaxNode, TextSize, T,
+};
+
+use crate::assist_config::SnippetCap;
+
+pub(crate) use insert_use::{find_insert_use_container, insert_use_statement};
+
+pub(crate) fn unwrap_trivial_block(block: ast::BlockExpr) -> ast::Expr {
+    extract_trivial_expression(&block)
+        .filter(|expr| !expr.syntax().text().contains_char('\n'))
+        .unwrap_or_else(|| block.into())
+}
+
+pub fn extract_trivial_expression(block: &ast::BlockExpr) -> Option<ast::Expr> {
+    let has_anything_else = |thing: &SyntaxNode| -> bool {
+        let mut non_trivial_children =
+            block.syntax().children_with_tokens().filter(|it| match it.kind() {
+                WHITESPACE | T!['{'] | T!['}'] => false,
+                _ => it.as_node() != Some(thing),
+            });
+        non_trivial_children.next().is_some()
+    };
+
+    if let Some(expr) = block.expr() {
+        if has_anything_else(expr.syntax()) {
+            return None;
+        }
+        return Some(expr);
+    }
+    // Unwrap `{ continue; }`
+    let (stmt,) = block.statements().next_tuple()?;
+    if let ast::Stmt::ExprStmt(expr_stmt) = stmt {
+        if has_anything_else(expr_stmt.syntax()) {
+            return None;
+        }
+        let expr = expr_stmt.expr()?;
+        match expr.syntax().kind() {
+            CONTINUE_EXPR | BREAK_EXPR | RETURN_EXPR => return Some(expr),
+            _ => (),
+        }
+    }
+    None
+}
+
+#[derive(Clone, Copy, Debug)]
+pub(crate) enum Cursor<'a> {
+    Replace(&'a SyntaxNode),
+    Before(&'a SyntaxNode),
+}
+
+impl<'a> Cursor<'a> {
+    fn node(self) -> &'a SyntaxNode {
+        match self {
+            Cursor::Replace(node) | Cursor::Before(node) => node,
+        }
+    }
+}
+
+pub(crate) fn render_snippet(_cap: SnippetCap, node: &SyntaxNode, cursor: Cursor) -> String {
+    assert!(cursor.node().ancestors().any(|it| it == *node));
+    let range = cursor.node().text_range() - node.text_range().start();
+    let range: ops::Range<usize> = range.into();
+
+    let mut placeholder = cursor.node().to_string();
+    escape(&mut placeholder);
+    let tab_stop = match cursor {
+        Cursor::Replace(placeholder) => format!("${{0:{}}}", placeholder),
+        Cursor::Before(placeholder) => format!("$0{}", placeholder),
+    };
+
+    let mut buf = node.to_string();
+    buf.replace_range(range, &tab_stop);
+    return buf;
+
+    fn escape(buf: &mut String) {
+        stdx::replace(buf, '{', r"\{");
+        stdx::replace(buf, '}', r"\}");
+        stdx::replace(buf, '$', r"\$");
+    }
+}
+
+pub fn get_missing_assoc_items(
+    sema: &Semantics<RootDatabase>,
+    impl_def: &ast::Impl,
+) -> Vec<hir::AssocItem> {
+    // Names must be unique between constants and functions. However, type aliases
+    // may share the same name as a function or constant.
+    let mut impl_fns_consts = FxHashSet::default();
+    let mut impl_type = FxHashSet::default();
+
+    if let Some(item_list) = impl_def.assoc_item_list() {
+        for item in item_list.assoc_items() {
+            match item {
+                ast::AssocItem::Fn(f) => {
+                    if let Some(n) = f.name() {
+                        impl_fns_consts.insert(n.syntax().to_string());
+                    }
+                }
+
+                ast::AssocItem::TypeAlias(t) => {
+                    if let Some(n) = t.name() {
+                        impl_type.insert(n.syntax().to_string());
+                    }
+                }
+
+                ast::AssocItem::Const(c) => {
+                    if let Some(n) = c.name() {
+                        impl_fns_consts.insert(n.syntax().to_string());
+                    }
+                }
+                ast::AssocItem::MacroCall(_) => (),
+            }
+        }
+    }
+
+    resolve_target_trait(sema, impl_def).map_or(vec![], |target_trait| {
+        target_trait
+            .items(sema.db)
+            .iter()
+            .filter(|i| match i {
+                hir::AssocItem::Function(f) => {
+                    !impl_fns_consts.contains(&f.name(sema.db).to_string())
+                }
+                hir::AssocItem::TypeAlias(t) => !impl_type.contains(&t.name(sema.db).to_string()),
+                hir::AssocItem::Const(c) => c
+                    .name(sema.db)
+                    .map(|n| !impl_fns_consts.contains(&n.to_string()))
+                    .unwrap_or_default(),
+            })
+            .cloned()
+            .collect()
+    })
+}
+
+pub(crate) fn resolve_target_trait(
+    sema: &Semantics<RootDatabase>,
+    impl_def: &ast::Impl,
+) -> Option<hir::Trait> {
+    let ast_path =
+        impl_def.trait_().map(|it| it.syntax().clone()).and_then(ast::PathType::cast)?.path()?;
+
+    match sema.resolve_path(&ast_path) {
+        Some(hir::PathResolution::Def(hir::ModuleDef::Trait(def))) => Some(def),
+        _ => None,
+    }
+}
+
+pub(crate) fn vis_offset(node: &SyntaxNode) -> TextSize {
+    node.children_with_tokens()
+        .find(|it| !matches!(it.kind(), WHITESPACE | COMMENT | ATTR))
+        .map(|it| it.text_range().start())
+        .unwrap_or_else(|| node.text_range().start())
+}
+
+pub(crate) fn invert_boolean_expression(expr: ast::Expr) -> ast::Expr {
+    if let Some(expr) = invert_special_case(&expr) {
+        return expr;
+    }
+    make::expr_prefix(T![!], expr)
+}
+
+fn invert_special_case(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()),
+            ast::BinOp::EqualityTest => bin.replace_op(T![!=]).map(|it| it.into()),
+            _ => None,
+        },
+        ast::Expr::PrefixExpr(pe) if pe.op_kind()? == ast::PrefixOp::Not => pe.expr(),
+        // FIXME:
+        // ast::Expr::Literal(true | false )
+        _ => None,
+    }
+}
+
+#[derive(Clone, Copy)]
+pub enum TryEnum {
+    Result,
+    Option,
+}
+
+impl TryEnum {
+    const ALL: [TryEnum; 2] = [TryEnum::Option, TryEnum::Result];
+
+    pub fn from_ty(sema: &Semantics<RootDatabase>, ty: &Type) -> Option<TryEnum> {
+        let enum_ = match ty.as_adt() {
+            Some(Adt::Enum(it)) => it,
+            _ => return None,
+        };
+        TryEnum::ALL.iter().find_map(|&var| {
+            if &enum_.name(sema.db).to_string() == var.type_name() {
+                return Some(var);
+            }
+            None
+        })
+    }
+
+    pub(crate) fn happy_case(self) -> &'static str {
+        match self {
+            TryEnum::Result => "Ok",
+            TryEnum::Option => "Some",
+        }
+    }
+
+    pub(crate) fn sad_pattern(self) -> ast::Pat {
+        match self {
+            TryEnum::Result => make::tuple_struct_pat(
+                make::path_unqualified(make::path_segment(make::name_ref("Err"))),
+                iter::once(make::wildcard_pat().into()),
+            )
+            .into(),
+            TryEnum::Option => make::ident_pat(make::name("None")).into(),
+        }
+    }
+
+    fn type_name(self) -> &'static str {
+        match self {
+            TryEnum::Result => "Result",
+            TryEnum::Option => "Option",
+        }
+    }
+}
+
+/// Helps with finding well-know things inside the standard library. This is
+/// somewhat similar to the known paths infra inside hir, but it different; We
+/// want to make sure that IDE specific paths don't become interesting inside
+/// the compiler itself as well.
+pub(crate) struct FamousDefs<'a, 'b>(pub(crate) &'a Semantics<'b, RootDatabase>, pub(crate) Crate);
+
+#[allow(non_snake_case)]
+impl FamousDefs<'_, '_> {
+    #[cfg(test)]
+    pub(crate) const FIXTURE: &'static str = r#"//- /libcore.rs crate:core
+pub mod convert {
+    pub trait From<T> {
+        fn from(T) -> Self;
+    }
+}
+
+pub mod option {
+    pub enum Option<T> { None, Some(T)}
+}
+
+pub mod prelude {
+    pub use crate::{convert::From, option::Option::{self, *}};
+}
+#[prelude_import]
+pub use prelude::*;
+"#;
+
+    pub(crate) fn core_convert_From(&self) -> Option<Trait> {
+        self.find_trait("core:convert:From")
+    }
+
+    pub(crate) fn core_option_Option(&self) -> Option<Enum> {
+        self.find_enum("core:option:Option")
+    }
+
+    fn find_trait(&self, path: &str) -> Option<Trait> {
+        match self.find_def(path)? {
+            hir::ScopeDef::ModuleDef(hir::ModuleDef::Trait(it)) => Some(it),
+            _ => None,
+        }
+    }
+
+    fn find_enum(&self, path: &str) -> Option<Enum> {
+        match self.find_def(path)? {
+            hir::ScopeDef::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Enum(it))) => Some(it),
+            _ => None,
+        }
+    }
+
+    fn find_def(&self, path: &str) -> Option<ScopeDef> {
+        let db = self.0.db;
+        let mut path = path.split(':');
+        let trait_ = path.next_back()?;
+        let std_crate = path.next()?;
+        let std_crate = self
+            .1
+            .dependencies(db)
+            .into_iter()
+            .find(|dep| &dep.name.to_string() == std_crate)?
+            .krate;
+
+        let mut module = std_crate.root_module(db);
+        for segment in path {
+            module = module.children(db).find_map(|child| {
+                let name = child.name(db)?;
+                if &name.to_string() == segment {
+                    Some(child)
+                } else {
+                    None
+                }
+            })?;
+        }
+        let def =
+            module.scope(db, None).into_iter().find(|(name, _def)| &name.to_string() == trait_)?.1;
+        Some(def)
+    }
+}