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|
use hir::HirDisplay;
use syntax::{ast, AstNode, TextSize};
use test_utils::mark;
use crate::{AssistContext, AssistId, AssistKind, Assists};
// Assist: infer_function_return_type
//
// Adds the return type to a function inferred from its tail expression if it doesn't have a return
// type specified.
//
// ```
// fn foo() { 4<|>2i32 }
// ```
// ->
// ```
// fn foo() -> i32 { 42i32 }
// ```
pub(crate) fn infer_function_return_type(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
let expr = ctx.find_node_at_offset::<ast::Expr>()?;
let func = expr.syntax().ancestors().find_map(ast::Fn::cast)?;
if func.ret_type().is_some() {
mark::hit!(existing_ret_type);
return None;
}
let body = func.body()?;
let tail_expr = body.expr()?;
// check whether the expr we were at is indeed the tail expression
if !tail_expr.syntax().text_range().contains_range(expr.syntax().text_range()) {
mark::hit!(not_tail_expr);
return None;
}
let module = ctx.sema.scope(func.syntax()).module()?;
let ty = ctx.sema.type_of_expr(&tail_expr)?;
let ty = ty.display_source_code(ctx.db(), module.into()).ok()?;
let rparen = func.param_list()?.r_paren_token()?;
acc.add(
AssistId("change_return_type_to_result", AssistKind::RefactorRewrite),
"Wrap return type in Result",
tail_expr.syntax().text_range(),
|builder| {
let insert_pos = rparen.text_range().end() + TextSize::from(1);
builder.insert(insert_pos, &format!("-> {} ", ty));
},
)
}
#[cfg(test)]
mod tests {
use crate::tests::{check_assist, check_assist_not_applicable};
use super::*;
#[test]
fn infer_return_type() {
check_assist(
infer_function_return_type,
r#"fn foo() {
45<|>
}"#,
r#"fn foo() -> i32 {
45
}"#,
);
}
#[test]
fn infer_return_type_nested() {
check_assist(
infer_function_return_type,
r#"fn foo() {
if true {
3<|>
} else {
5
}
}"#,
r#"fn foo() -> i32 {
if true {
3
} else {
5
}
}"#,
);
}
#[test]
fn not_applicable_ret_type_specified() {
mark::check!(existing_ret_type);
check_assist_not_applicable(
infer_function_return_type,
r#"fn foo() -> i32 {
( 45<|> + 32 ) * 123
}"#,
);
}
#[test]
fn not_applicable_non_tail_expr() {
mark::check!(not_tail_expr);
check_assist_not_applicable(
infer_function_return_type,
r#"fn foo() {
let x = <|>3;
( 45 + 32 ) * 123
}"#,
);
}
}
|
