use either::Either;
use hir::{CallableKind, ClosureStyle, HirDisplay, InFile, db::ExpandDatabase};
use ide_db::{
    famous_defs::FamousDefs,
    source_change::{SourceChange, SourceChangeBuilder},
    text_edit::TextEdit,
};
use syntax::{
    AstNode, AstPtr, TextSize,
    ast::{
        self, BlockExpr, Expr, ExprStmt, HasArgList,
        edit::{AstNodeEdit, IndentLevel},
        syntax_factory::SyntaxFactory,
    },
};

use crate::{Assist, Diagnostic, DiagnosticCode, DiagnosticsContext, adjusted_display_range, fix};

// Diagnostic: type-mismatch
//
// This diagnostic is triggered when the type of an expression or pattern does not match
// the expected type.
pub(crate) fn type_mismatch(ctx: &DiagnosticsContext<'_>, d: &hir::TypeMismatch<'_>) -> Diagnostic {
    let display_range = adjusted_display_range(ctx, d.expr_or_pat, &|node| {
        let Either::Left(expr) = node else { return None };
        let salient_token_range = match expr {
            ast::Expr::IfExpr(it) => it.if_token()?.text_range(),
            ast::Expr::LoopExpr(it) => it.loop_token()?.text_range(),
            ast::Expr::ForExpr(it) => it.for_token()?.text_range(),
            ast::Expr::WhileExpr(it) => it.while_token()?.text_range(),
            ast::Expr::BlockExpr(it) => it.stmt_list()?.r_curly_token()?.text_range(),
            ast::Expr::MatchExpr(it) => it.match_token()?.text_range(),
            ast::Expr::MethodCallExpr(it) => it.name_ref()?.ident_token()?.text_range(),
            ast::Expr::FieldExpr(it) => it.name_ref()?.ident_token()?.text_range(),
            ast::Expr::AwaitExpr(it) => it.await_token()?.text_range(),
            _ => return None,
        };

        cov_mark::hit!(type_mismatch_range_adjustment);
        Some(salient_token_range)
    });
    Diagnostic::new(
        DiagnosticCode::RustcHardError("E0308"),
        format!(
            "expected {}, found {}",
            d.expected
                .display(ctx.sema.db, ctx.display_target)
                .with_closure_style(ClosureStyle::ClosureWithId),
            d.actual
                .display(ctx.sema.db, ctx.display_target)
                .with_closure_style(ClosureStyle::ClosureWithId),
        ),
        display_range,
    )
    .stable()
    .with_fixes(fixes(ctx, d))
}

fn fixes(ctx: &DiagnosticsContext<'_>, d: &hir::TypeMismatch<'_>) -> Option<Vec<Assist>> {
    let mut fixes = Vec::new();

    if let Some(expr_ptr) = d.expr_or_pat.value.cast::<ast::Expr>() {
        let expr_ptr = &InFile { file_id: d.expr_or_pat.file_id, value: expr_ptr };
        add_reference(ctx, d, expr_ptr, &mut fixes);
        add_missing_ok_or_some(ctx, d, expr_ptr, &mut fixes);
        remove_unnecessary_wrapper(ctx, d, expr_ptr, &mut fixes);
        remove_semicolon(ctx, d, expr_ptr, &mut fixes);
        str_ref_to_owned(ctx, d, expr_ptr, &mut fixes);
    }

    if fixes.is_empty() { None } else { Some(fixes) }
}

fn add_reference(
    ctx: &DiagnosticsContext<'_>,
    d: &hir::TypeMismatch<'_>,
    expr_ptr: &InFile<AstPtr<ast::Expr>>,
    acc: &mut Vec<Assist>,
) -> Option<()> {
    let range = ctx.sema.diagnostics_display_range((*expr_ptr).map(|it| it.into()));

    let (_, mutability) = d.expected.as_reference()?;
    let actual_with_ref = d.actual.add_reference(mutability);
    if !actual_with_ref.could_coerce_to(ctx.sema.db, &d.expected) {
        return None;
    }

    let ampersands = format!("&{}", mutability.as_keyword_for_ref());

    let edit = TextEdit::insert(range.range.start(), ampersands);
    let source_change = SourceChange::from_text_edit(range.file_id, edit);
    acc.push(fix("add_reference_here", "Add reference here", source_change, range.range));
    Some(())
}

fn add_missing_ok_or_some(
    ctx: &DiagnosticsContext<'_>,
    d: &hir::TypeMismatch<'_>,
    expr_ptr: &InFile<AstPtr<ast::Expr>>,
    acc: &mut Vec<Assist>,
) -> Option<()> {
    let root = ctx.sema.db.parse_or_expand(expr_ptr.file_id);
    let expr = expr_ptr.value.to_node(&root);
    let expr_range = expr.syntax().text_range();
    let scope = ctx.sema.scope(expr.syntax())?;

    let expected_adt = d.expected.as_adt()?;
    let expected_enum = expected_adt.as_enum()?;

    let famous_defs = FamousDefs(&ctx.sema, scope.krate());
    let core_result = famous_defs.core_result_Result();
    let core_option = famous_defs.core_option_Option();

    if Some(expected_enum) != core_result && Some(expected_enum) != core_option {
        return None;
    }

    let variant_name = if Some(expected_enum) == core_result { "Ok" } else { "Some" };

    let wrapped_actual_ty =
        expected_adt.ty_with_args(ctx.sema.db, std::iter::once(d.actual.clone()));

    if !d.expected.could_unify_with(ctx.sema.db, &wrapped_actual_ty) {
        return None;
    }

    if d.actual.is_unit() {
        if let Expr::BlockExpr(block) = &expr {
            if block.tail_expr().is_none() {
                // Fix for forms like `fn foo() -> Result<(), String> {}`
                let mut builder = TextEdit::builder();
                let block_indent = block.indent_level();

                if block.statements().count() == 0 {
                    // Empty block
                    let indent = block_indent + 1;
                    builder.insert(
                        block.syntax().text_range().start() + TextSize::from(1),
                        format!("\n{indent}{variant_name}(())\n{block_indent}"),
                    );
                } else {
                    let indent = IndentLevel::from(1);
                    builder.insert(
                        block.syntax().text_range().end() - TextSize::from(1),
                        format!("{indent}{variant_name}(())\n{block_indent}"),
                    );
                }

                let source_change = SourceChange::from_text_edit(
                    expr_ptr.file_id.original_file(ctx.sema.db).file_id(ctx.sema.db),
                    builder.finish(),
                );
                let name = format!("Insert {variant_name}(()) as the tail of this block");
                acc.push(fix("insert_wrapped_unit", &name, source_change, expr_range));
            }
            return Some(());
        } else if let Expr::ReturnExpr(ret_expr) = &expr {
            // Fix for forms like `fn foo() -> Result<(), String> { return; }`
            if ret_expr.expr().is_none() {
                let mut builder = TextEdit::builder();
                builder
                    .insert(ret_expr.syntax().text_range().end(), format!(" {variant_name}(())"));
                let source_change = SourceChange::from_text_edit(
                    expr_ptr.file_id.original_file(ctx.sema.db).file_id(ctx.sema.db),
                    builder.finish(),
                );
                let name = format!("Insert {variant_name}(()) as the return value");
                acc.push(fix("insert_wrapped_unit", &name, source_change, expr_range));
            }
            return Some(());
        }
    }

    let mut builder = TextEdit::builder();
    builder.insert(expr.syntax().text_range().start(), format!("{variant_name}("));
    builder.insert(expr.syntax().text_range().end(), ")".to_owned());
    let source_change = SourceChange::from_text_edit(
        expr_ptr.file_id.original_file(ctx.sema.db).file_id(ctx.sema.db),
        builder.finish(),
    );
    let name = format!("Wrap in {variant_name}");
    acc.push(fix("wrap_in_constructor", &name, source_change, expr_range));
    Some(())
}

fn remove_unnecessary_wrapper(
    ctx: &DiagnosticsContext<'_>,
    d: &hir::TypeMismatch<'_>,
    expr_ptr: &InFile<AstPtr<ast::Expr>>,
    acc: &mut Vec<Assist>,
) -> Option<()> {
    let db = ctx.sema.db;
    let root = db.parse_or_expand(expr_ptr.file_id);
    let expr = expr_ptr.value.to_node(&root);
    let expr = ctx.sema.original_ast_node(expr)?;

    let Expr::CallExpr(call_expr) = expr else {
        return None;
    };

    let callable = ctx.sema.resolve_expr_as_callable(&call_expr.expr()?)?;
    let CallableKind::TupleEnumVariant(variant) = callable.kind() else {
        return None;
    };

    let actual_enum = d.actual.as_adt()?.as_enum()?;
    let famous_defs = FamousDefs(&ctx.sema, ctx.sema.scope(call_expr.syntax())?.krate());
    let core_option = famous_defs.core_option_Option();
    let core_result = famous_defs.core_result_Result();
    if Some(actual_enum) != core_option && Some(actual_enum) != core_result {
        return None;
    }

    let inner_type = variant.fields(db).first()?.ty_with_args(db, d.actual.type_arguments());
    if !d.expected.could_unify_with(db, &inner_type) {
        return None;
    }

    let inner_arg = call_expr.arg_list()?.args().next()?;

    let file_id = expr_ptr.file_id.original_file(db);
    let mut builder = SourceChangeBuilder::new(file_id.file_id(ctx.sema.db));
    let mut editor;
    match inner_arg {
        // We're returning `()`
        Expr::TupleExpr(tup) if tup.fields().next().is_none() => {
            let parent = call_expr
                .syntax()
                .parent()
                .and_then(Either::<ast::ReturnExpr, ast::StmtList>::cast)?;

            editor = builder.make_editor(parent.syntax());
            let make = SyntaxFactory::with_mappings();

            match parent {
                Either::Left(ret_expr) => {
                    editor.replace(ret_expr.syntax(), make.expr_return(None).syntax());
                }
                Either::Right(stmt_list) => {
                    let new_block = if stmt_list.statements().next().is_none() {
                        make.expr_empty_block()
                    } else {
                        make.block_expr(stmt_list.statements(), None)
                    };

                    editor.replace(stmt_list.syntax().parent()?, new_block.syntax());
                }
            }

            editor.add_mappings(make.finish_with_mappings());
        }
        _ => {
            editor = builder.make_editor(call_expr.syntax());
            editor.replace(call_expr.syntax(), inner_arg.syntax());
        }
    }

    builder.add_file_edits(file_id.file_id(ctx.sema.db), editor);
    let name = format!("Remove unnecessary {}() wrapper", variant.name(db).as_str());
    acc.push(fix(
        "remove_unnecessary_wrapper",
        &name,
        builder.finish(),
        call_expr.syntax().text_range(),
    ));
    Some(())
}

fn remove_semicolon(
    ctx: &DiagnosticsContext<'_>,
    d: &hir::TypeMismatch<'_>,
    expr_ptr: &InFile<AstPtr<ast::Expr>>,
    acc: &mut Vec<Assist>,
) -> Option<()> {
    let root = ctx.sema.db.parse_or_expand(expr_ptr.file_id);
    let expr = expr_ptr.value.to_node(&root);
    if !d.actual.is_unit() {
        return None;
    }
    let block = BlockExpr::cast(expr.syntax().clone())?;
    let expr_before_semi =
        block.statements().last().and_then(|s| ExprStmt::cast(s.syntax().clone()))?;
    let type_before_semi = ctx.sema.type_of_expr(&expr_before_semi.expr()?)?.original();
    if !type_before_semi.could_coerce_to(ctx.sema.db, &d.expected) {
        return None;
    }
    let semicolon_range = expr_before_semi.semicolon_token()?.text_range();

    let edit = TextEdit::delete(semicolon_range);
    let source_change = SourceChange::from_text_edit(
        expr_ptr.file_id.original_file(ctx.sema.db).file_id(ctx.sema.db),
        edit,
    );

    acc.push(fix("remove_semicolon", "Remove this semicolon", source_change, semicolon_range));
    Some(())
}

fn str_ref_to_owned(
    ctx: &DiagnosticsContext<'_>,
    d: &hir::TypeMismatch<'_>,
    expr_ptr: &InFile<AstPtr<ast::Expr>>,
    acc: &mut Vec<Assist>,
) -> Option<()> {
    let expected = d.expected.display(ctx.sema.db, ctx.display_target);
    // FIXME do this properly
    let is_applicable = d.actual.strip_reference().is_str() && expected.to_string() == "String";
    if !is_applicable {
        return None;
    }

    let root = ctx.sema.db.parse_or_expand(expr_ptr.file_id);
    let expr = expr_ptr.value.to_node(&root);
    let expr_range = expr.syntax().text_range();

    let to_owned = ".to_owned()".to_owned();

    let edit = TextEdit::insert(expr.syntax().text_range().end(), to_owned);
    let source_change = SourceChange::from_text_edit(
        expr_ptr.file_id.original_file(ctx.sema.db).file_id(ctx.sema.db),
        edit,
    );
    acc.push(fix("str_ref_to_owned", "Add .to_owned() here", source_change, expr_range));

    Some(())
}

#[cfg(test)]
mod tests {
    use crate::tests::{
        check_diagnostics, check_diagnostics_with_disabled, check_fix, check_has_fix, check_no_fix,
    };

    #[test]
    fn missing_reference() {
        check_diagnostics(
            r#"
fn main() {
    test(123);
       //^^^ 💡 error: expected &i32, found i32
}
fn test(_arg: &i32) {}
"#,
        );
    }

    #[test]
    fn add_reference_to_int() {
        check_fix(
            r#"
fn main() {
    test(123$0);
}
fn test(_arg: &i32) {}
            "#,
            r#"
fn main() {
    test(&123);
}
fn test(_arg: &i32) {}
            "#,
        );
    }

    #[test]
    fn add_mutable_reference_to_int() {
        check_fix(
            r#"
fn main() {
    test($0123);
}
fn test(_arg: &mut i32) {}
            "#,
            r#"
fn main() {
    test(&mut 123);
}
fn test(_arg: &mut i32) {}
            "#,
        );
    }

    #[test]
    fn add_reference_to_array() {
        check_fix(
            r#"
//- minicore: coerce_unsized
fn main() {
    test($0[1, 2, 3]);
}
fn test(_arg: &[i32]) {}
            "#,
            r#"
fn main() {
    test(&[1, 2, 3]);
}
fn test(_arg: &[i32]) {}
            "#,
        );
    }

    #[test]
    fn add_reference_with_autoderef() {
        check_fix(
            r#"
//- minicore: coerce_unsized, deref
struct Foo;
struct Bar;
impl core::ops::Deref for Foo {
    type Target = Bar;
    fn deref(&self) -> &Self::Target { loop {} }
}

fn main() {
    test($0Foo);
}
fn test(_arg: &Bar) {}
            "#,
            r#"
struct Foo;
struct Bar;
impl core::ops::Deref for Foo {
    type Target = Bar;
    fn deref(&self) -> &Self::Target { loop {} }
}

fn main() {
    test(&Foo);
}
fn test(_arg: &Bar) {}
            "#,
        );
    }

    #[test]
    fn add_reference_to_method_call() {
        check_fix(
            r#"
fn main() {
    Test.call_by_ref($0123);
}
struct Test;
impl Test {
    fn call_by_ref(&self, _arg: &i32) {}
}
            "#,
            r#"
fn main() {
    Test.call_by_ref(&123);
}
struct Test;
impl Test {
    fn call_by_ref(&self, _arg: &i32) {}
}
            "#,
        );
    }

    #[test]
    fn add_reference_to_let_stmt() {
        check_fix(
            r#"
fn main() {
    let test: &i32 = $0123;
}
            "#,
            r#"
fn main() {
    let test: &i32 = &123;
}
            "#,
        );
    }

    #[test]
    fn add_reference_to_macro_call() {
        check_fix(
            r#"
macro_rules! thousand {
    () => {
        1000_u64
    };
}
fn test(_foo: &u64) {}
fn main() {
    test($0thousand!());
}
            "#,
            r#"
macro_rules! thousand {
    () => {
        1000_u64
    };
}
fn test(_foo: &u64) {}
fn main() {
    test(&thousand!());
}
            "#,
        );
    }

    #[test]
    fn add_mutable_reference_to_let_stmt() {
        check_fix(
            r#"
fn main() {
    let _test: &mut i32 = $0123;
}
            "#,
            r#"
fn main() {
    let _test: &mut i32 = &mut 123;
}
            "#,
        );
    }

    #[test]
    fn const_generic_type_mismatch() {
        check_diagnostics(
            r#"
            pub struct Rate<const N: u32>;
            fn f<const N: u64>() -> Rate<N> { // FIXME: add some error
                loop {}
            }
            fn run(_t: Rate<5>) {
            }
            fn main() {
                run(f())
            }
"#,
        );
    }

    #[test]
    fn const_generic_unknown() {
        check_diagnostics(
            r#"
            pub struct Rate<T, const NOM: u32, const DENOM: u32>(T);
            fn run(_t: Rate<u32, 1, 1>) {
            }
            fn main() {
                run(Rate::<_, _, _>(5));
            }
"#,
        );
    }

    #[test]
    fn wrap_return_type() {
        check_fix(
            r#"
//- minicore: option, result
fn div(x: i32, y: i32) -> Result<i32, ()> {
    if y == 0 {
        return Err(());
    }
    x / y$0
}
"#,
            r#"
fn div(x: i32, y: i32) -> Result<i32, ()> {
    if y == 0 {
        return Err(());
    }
    Ok(x / y)
}
"#,
        );
    }

    #[test]
    fn wrap_return_type_option() {
        check_fix(
            r#"
//- minicore: option, result
fn div(x: i32, y: i32) -> Option<i32> {
    if y == 0 {
        return None;
    }
    x / y$0
}
"#,
            r#"
fn div(x: i32, y: i32) -> Option<i32> {
    if y == 0 {
        return None;
    }
    Some(x / y)
}
"#,
        );
    }

    #[test]
    fn wrap_return_type_option_tails() {
        check_fix(
            r#"
//- minicore: option, result
fn div(x: i32, y: i32) -> Option<i32> {
    if y == 0 {
        Some(0)
    } else if true {
        100$0
    } else {
        None
    }
}
"#,
            r#"
fn div(x: i32, y: i32) -> Option<i32> {
    if y == 0 {
        Some(0)
    } else if true {
        Some(100)
    } else {
        None
    }
}
"#,
        );
    }

    #[test]
    fn wrap_return_type_handles_generic_functions() {
        check_fix(
            r#"
//- minicore: option, result
fn div<T>(x: T) -> Result<T, i32> {
    if x == 0 {
        return Err(7);
    }
    $0x
}
"#,
            r#"
fn div<T>(x: T) -> Result<T, i32> {
    if x == 0 {
        return Err(7);
    }
    Ok(x)
}
"#,
        );
    }

    #[test]
    fn wrap_return_type_handles_type_aliases() {
        check_fix(
            r#"
//- minicore: option, result
type MyResult<T> = Result<T, ()>;

fn div(x: i32, y: i32) -> MyResult<i32> {
    if y == 0 {
        return Err(());
    }
    x $0/ y
}
"#,
            r#"
type MyResult<T> = Result<T, ()>;

fn div(x: i32, y: i32) -> MyResult<i32> {
    if y == 0 {
        return Err(());
    }
    Ok(x / y)
}
"#,
        );
    }

    #[test]
    fn wrapped_unit_as_block_tail_expr() {
        check_fix(
            r#"
//- minicore: result
fn foo() -> Result<(), ()> {
    foo();
}$0
            "#,
            r#"
fn foo() -> Result<(), ()> {
    foo();
    Ok(())
}
            "#,
        );

        check_fix(
            r#"
//- minicore: result
fn foo() -> Result<(), ()> {}$0
            "#,
            r#"
fn foo() -> Result<(), ()> {
    Ok(())
}
            "#,
        );
    }

    #[test]
    fn wrapped_unit_as_return_expr() {
        check_fix(
            r#"
//- minicore: result
fn foo(b: bool) -> Result<(), String> {
    if b {
        return$0;
    }

    Err("oh dear".to_owned())
}"#,
            r#"
fn foo(b: bool) -> Result<(), String> {
    if b {
        return Ok(());
    }

    Err("oh dear".to_owned())
}"#,
        );
    }

    #[test]
    fn wrap_in_const_and_static() {
        check_fix(
            r#"
//- minicore: option, result
static A: Option<()> = {($0)};
            "#,
            r#"
static A: Option<()> = {Some(())};
            "#,
        );
        check_fix(
            r#"
//- minicore: option, result
const _: Option<()> = {($0)};
            "#,
            r#"
const _: Option<()> = {Some(())};
            "#,
        );
    }

    #[test]
    fn wrap_return_type_not_applicable_when_expr_type_does_not_match_ok_type() {
        check_no_fix(
            r#"
//- minicore: option, result
fn foo() -> Result<(), i32> { 0$0 }
"#,
        );
    }

    #[test]
    fn wrap_return_type_not_applicable_when_return_type_is_not_result_or_option() {
        check_no_fix(
            r#"
//- minicore: option, result
enum SomeOtherEnum { Ok(i32), Err(String) }

fn foo() -> SomeOtherEnum { 0$0 }
"#,
        );
    }

    #[test]
    fn unwrap_return_type() {
        check_fix(
            r#"
//- minicore: option, result
fn div(x: i32, y: i32) -> i32 {
    if y == 0 {
        panic!();
    }
    Ok(x / y)$0
}
"#,
            r#"
fn div(x: i32, y: i32) -> i32 {
    if y == 0 {
        panic!();
    }
    x / y
}
"#,
        );
    }

    #[test]
    fn unwrap_return_type_option() {
        check_fix(
            r#"
//- minicore: option, result
fn div(x: i32, y: i32) -> i32 {
    if y == 0 {
        panic!();
    }
    Some(x / y)$0
}
"#,
            r#"
fn div(x: i32, y: i32) -> i32 {
    if y == 0 {
        panic!();
    }
    x / y
}
"#,
        );
    }

    #[test]
    fn unwrap_return_type_option_tails() {
        check_fix(
            r#"
//- minicore: option, result
fn div(x: i32, y: i32) -> i32 {
    if y == 0 {
        42
    } else if true {
        Some(100)$0
    } else {
        0
    }
}
"#,
            r#"
fn div(x: i32, y: i32) -> i32 {
    if y == 0 {
        42
    } else if true {
        100
    } else {
        0
    }
}
"#,
        );
    }

    #[test]
    fn unwrap_return_type_option_tail_unit() {
        check_fix(
            r#"
//- minicore: option, result
fn div(x: i32, y: i32) {
    if y == 0 {
        panic!();
    }

    Ok(())$0
}
"#,
            r#"
fn div(x: i32, y: i32) {
    if y == 0 {
        panic!();
    }
}
"#,
        );
    }

    #[test]
    fn unwrap_return_type_handles_generic_functions() {
        check_fix(
            r#"
//- minicore: option, result
fn div<T>(x: T) -> T {
    if x == 0 {
        panic!();
    }
    $0Ok(x)
}
"#,
            r#"
fn div<T>(x: T) -> T {
    if x == 0 {
        panic!();
    }
    x
}
"#,
        );
    }

    #[test]
    fn unwrap_return_type_handles_type_aliases() {
        check_fix(
            r#"
//- minicore: option, result
type MyResult<T> = T;

fn div(x: i32, y: i32) -> MyResult<i32> {
    if y == 0 {
        panic!();
    }
    Ok(x $0/ y)
}
"#,
            r#"
type MyResult<T> = T;

fn div(x: i32, y: i32) -> MyResult<i32> {
    if y == 0 {
        panic!();
    }
    x / y
}
"#,
        );
    }

    #[test]
    fn unwrap_tail_expr() {
        check_fix(
            r#"
//- minicore: result
fn foo() -> () {
    println!("Hello, world!");
    Ok(())$0
}
            "#,
            r#"
fn foo() -> () {
    println!("Hello, world!");
}
            "#,
        );
    }

    #[test]
    fn unwrap_to_empty_block() {
        check_fix(
            r#"
//- minicore: result
fn foo() -> () {
    Ok(())$0
}
            "#,
            r#"
fn foo() -> () {}
            "#,
        );
    }

    #[test]
    fn unwrap_to_return_expr() {
        check_has_fix(
            r#"
//- minicore: result
fn foo(b: bool) -> () {
    if b {
        return $0Ok(());
    }

    panic!("oh dear");
}"#,
            r#"
fn foo(b: bool) -> () {
    if b {
        return;
    }

    panic!("oh dear");
}"#,
        );
    }

    #[test]
    fn unwrap_in_const_and_static() {
        check_fix(
            r#"
//- minicore: option, result
static A: () = {Some(($0))};
            "#,
            r#"
static A: () = {};
            "#,
        );
        check_fix(
            r#"
//- minicore: option, result
const _: () = {Some(($0))};
            "#,
            r#"
const _: () = {};
            "#,
        );
    }

    #[test]
    fn unwrap_return_type_not_applicable_when_inner_type_does_not_match_return_type() {
        check_no_fix(
            r#"
//- minicore: result
fn foo() -> i32 { $0Ok(()) }
"#,
        );
    }

    #[test]
    fn unwrap_return_type_not_applicable_when_wrapper_type_is_not_result_or_option() {
        check_no_fix(
            r#"
//- minicore: option, result
enum SomeOtherEnum { Ok(i32), Err(String) }

fn foo() -> i32 { SomeOtherEnum::Ok($042) }
"#,
        );
    }

    #[test]
    fn remove_semicolon() {
        check_fix(r#"fn f() -> i32 { 92$0; }"#, r#"fn f() -> i32 { 92 }"#);
    }

    #[test]
    fn str_ref_to_owned() {
        check_fix(
            r#"
struct String;

fn test() -> String {
    "a"$0
}
            "#,
            r#"
struct String;

fn test() -> String {
    "a".to_owned()
}
            "#,
        );
    }

    #[test]
    fn type_mismatch_range_adjustment() {
        cov_mark::check!(type_mismatch_range_adjustment);
        check_diagnostics(
            r#"
fn f() -> i32 {
    let x = 1;
    let y = 2;
    let _ = x + y;
  }
//^ error: expected i32, found ()

fn g() -> i32 {
    while true {}
} //^^^^^ error: expected i32, found ()

struct S;
impl S { fn foo(&self) -> &S { self } }
fn h() {
    let _: i32 = S.foo().foo().foo();
}                            //^^^ error: expected i32, found &S
"#,
        );
    }

    #[test]
    fn unknown_type_in_function_signature() {
        check_diagnostics(
            r#"
struct X<T>(T);

fn foo(_x: X<Unknown>) {}
fn test1() {
    // Unknown might be `i32`, so we should not emit type mismatch here.
    foo(X(42));
}
fn test2() {
    foo(42);
      //^^ error: expected X<{unknown}>, found i32
}
"#,
        );
    }

    #[test]
    fn evaluate_const_generics_in_types() {
        check_diagnostics(
            r#"
pub const ONE: usize = 1;

pub struct Inner<const P: usize>();

pub struct Outer {
    pub inner: Inner<ONE>,
}

fn main() {
    _ = Outer {
        inner: Inner::<2>(),
             //^^^^^^^^^^^^ error: expected Inner<1>, found Inner<2>
    };
}
"#,
        );
    }

    #[test]
    fn type_mismatch_pat_smoke_test() {
        check_diagnostics(
            r#"
fn f() {
    let &() = &mut ();
      //^^^ error: expected &mut (), found &()
    match &() {
        // FIXME: we should only show the deep one.
        &9 => ()
      //^^ error: expected &(), found &i32
       //^ error: expected (), found i32
    }
}
"#,
        );
    }

    #[test]
    fn regression_14768() {
        check_diagnostics(
            r#"
//- minicore: derive, fmt, slice, coerce_unsized, builtin_impls
use core::fmt::Debug;

#[derive(Debug)]
struct Foo(u8, u16, [u8]);

#[derive(Debug)]
struct Bar {
    f1: u8,
    f2: &[u16],
    f3: dyn Debug,
}
"#,
        );
    }

    #[test]
    fn trait_upcast_ok() {
        check_diagnostics(
            r#"
//- minicore: coerce_unsized
trait A: B {}
trait B {}

fn test(a: &dyn A) -> &dyn B {
    a
}
"#,
        );
    }

    #[test]
    fn trait_upcast_err() {
        check_diagnostics(
            r#"
//- minicore: coerce_unsized
trait A {} // `A` does not have `B` as a supertrait, so no upcast :c
trait B {}

fn test(a: &dyn A) -> &dyn B {
    a
  //^ error: expected &(dyn B + 'static), found &(dyn A + 'static)
}
"#,
        );
    }

    #[test]
    fn return_no_value() {
        check_diagnostics_with_disabled(
            r#"
fn f() -> i32 {
    return;
 // ^^^^^^ error: expected i32, found ()
    0
}
fn g() { return; }
"#,
            &["needless_return"],
        );
    }

    #[test]
    fn smoke_test_inner_items() {
        check_diagnostics(
            r#"
fn f() {
    fn inner() -> i32 {
        return;
     // ^^^^^^ error: expected i32, found ()
        0
    }
}
"#,
        );
    }

    #[test]
    fn regression_17585() {
        check_diagnostics(
            r#"
fn f() {
    let (_, _, _, ..) = (true, 42);
     // ^^^^^^^^^^^^^ error: expected (bool, i32), found (bool, i32, {unknown})
}
"#,
        );
    }

    #[test]
    fn complex_enum_variant_non_ref_pat() {
        check_diagnostics(
            r#"
enum Enum { Variant }

trait Trait {
    type Assoc;
}
impl Trait for () {
    type Assoc = Enum;
}

fn foo(v: &Enum) {
    let <Enum>::Variant = v;
    let <() as Trait>::Assoc::Variant = v;
}
    "#,
        );
    }

    #[test]
    fn regression_19844() {
        check_diagnostics(
            r#"
fn main() {
    struct S {}
    enum E { V() }
    let E::V() = &S {};
     // ^^^^^^ error: expected S, found E
}
"#,
        );
    }
}