Auto merge of #12130 - weirane:let-else-let-match, r=weirane

Turn let-else statements into let and match

Fixes #11906.

3 files changed, 519 insertions, 0 deletions

diff --git a/crates/ide-assists/src/handlers/convert_let_else_to_match.rs b/crates/ide-assists/src/handlers/convert_let_else_to_match.rs
new file mode 100644
index 00000000000..2363aa7cbd9
--- /dev/null
+++ b/crates/ide-assists/src/handlers/convert_let_else_to_match.rs
@@ -0,0 +1,497 @@
+use hir::Semantics;
+use ide_db::RootDatabase;
+use syntax::ast::{edit::AstNodeEdit, AstNode, HasName, LetStmt, Name, Pat};
+use syntax::T;
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+/// Gets a list of binders in a pattern, and whether they are mut.
+fn binders_in_pat(
+    acc: &mut Vec<(Name, bool)>,
+    pat: &Pat,
+    sem: &Semantics<RootDatabase>,
+) -> Option<()> {
+    use Pat::*;
+    match pat {
+        IdentPat(p) => {
+            let ident = p.name()?;
+            let ismut = p.ref_token().is_none() && p.mut_token().is_some();
+            // check for const reference
+            if sem.resolve_bind_pat_to_const(p).is_none() {
+                acc.push((ident, ismut));
+            }
+            if let Some(inner) = p.pat() {
+                binders_in_pat(acc, &inner, sem)?;
+            }
+            Some(())
+        }
+        BoxPat(p) => p.pat().and_then(|p| binders_in_pat(acc, &p, sem)),
+        RestPat(_) | LiteralPat(_) | PathPat(_) | WildcardPat(_) | ConstBlockPat(_) => Some(()),
+        OrPat(p) => {
+            for p in p.pats() {
+                binders_in_pat(acc, &p, sem)?;
+            }
+            Some(())
+        }
+        ParenPat(p) => p.pat().and_then(|p| binders_in_pat(acc, &p, sem)),
+        RangePat(p) => {
+            if let Some(st) = p.start() {
+                binders_in_pat(acc, &st, sem)?
+            }
+            if let Some(ed) = p.end() {
+                binders_in_pat(acc, &ed, sem)?
+            }
+            Some(())
+        }
+        RecordPat(p) => {
+            for f in p.record_pat_field_list()?.fields() {
+                let pat = f.pat()?;
+                binders_in_pat(acc, &pat, sem)?;
+            }
+            Some(())
+        }
+        RefPat(p) => p.pat().and_then(|p| binders_in_pat(acc, &p, sem)),
+        SlicePat(p) => {
+            for p in p.pats() {
+                binders_in_pat(acc, &p, sem)?;
+            }
+            Some(())
+        }
+        TuplePat(p) => {
+            for p in p.fields() {
+                binders_in_pat(acc, &p, sem)?;
+            }
+            Some(())
+        }
+        TupleStructPat(p) => {
+            for p in p.fields() {
+                binders_in_pat(acc, &p, sem)?;
+            }
+            Some(())
+        }
+        // don't support macro pat yet
+        MacroPat(_) => None,
+    }
+}
+
+fn binders_to_str(binders: &[(Name, bool)], addmut: bool) -> String {
+    let vars = binders
+        .iter()
+        .map(
+            |(ident, ismut)| {
+                if *ismut && addmut {
+                    format!("mut {}", ident)
+                } else {
+                    ident.to_string()
+                }
+            },
+        )
+        .collect::<Vec<_>>()
+        .join(", ");
+    if binders.is_empty() {
+        String::from("{}")
+    } else if binders.len() == 1 {
+        vars
+    } else {
+        format!("({})", vars)
+    }
+}
+
+// Assist: convert_let_else_to_match
+//
+// Converts let-else statement to let statement and match expression.
+//
+// ```
+// fn main() {
+//     let Ok(mut x) = f() else$0 { return };
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     let mut x = match f() {
+//         Ok(x) => x,
+//         _ => return,
+//     };
+// }
+// ```
+pub(crate) fn convert_let_else_to_match(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    // should focus on else token to trigger
+    let else_token = ctx.find_token_syntax_at_offset(T![else])?;
+    let let_stmt = LetStmt::cast(else_token.parent()?.parent()?)?;
+    let let_else_block = let_stmt.let_else()?.block_expr()?;
+    let let_init = let_stmt.initializer()?;
+    if let_stmt.ty().is_some() {
+        // don't support let with type annotation
+        return None;
+    }
+    let pat = let_stmt.pat()?;
+    let mut binders = Vec::new();
+    binders_in_pat(&mut binders, &pat, &ctx.sema)?;
+
+    let target = let_stmt.syntax().text_range();
+    acc.add(
+        AssistId("convert_let_else_to_match", AssistKind::RefactorRewrite),
+        "Convert let-else to let and match",
+        target,
+        |edit| {
+            let indent_level = let_stmt.indent_level().0 as usize;
+            let indent = "    ".repeat(indent_level);
+            let indent1 = "    ".repeat(indent_level + 1);
+
+            let binders_str = binders_to_str(&binders, false);
+            let binders_str_mut = binders_to_str(&binders, true);
+
+            let init_expr = let_init.syntax().text();
+            let mut pat_no_mut = pat.syntax().text().to_string();
+            // remove the mut from the pattern
+            for (b, ismut) in binders.iter() {
+                if *ismut {
+                    pat_no_mut = pat_no_mut.replace(&format!("mut {b}"), &b.to_string());
+                }
+            }
+
+            let only_expr = let_else_block.statements().next().is_none();
+            let branch2 = match &let_else_block.tail_expr() {
+                Some(tail) if only_expr => format!("{},", tail.syntax().text()),
+                _ => let_else_block.syntax().text().to_string(),
+            };
+            let replace = if binders.is_empty() {
+                format!(
+                    "match {init_expr} {{
+{indent1}{pat_no_mut} => {binders_str}
+{indent1}_ => {branch2}
+{indent}}}"
+                )
+            } else {
+                format!(
+                    "let {binders_str_mut} = match {init_expr} {{
+{indent1}{pat_no_mut} => {binders_str},
+{indent1}_ => {branch2}
+{indent}}};"
+                )
+            };
+            edit.replace(target, replace);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::tests::{check_assist, check_assist_not_applicable, check_assist_target};
+
+    #[test]
+    fn convert_let_else_to_match_no_type_let() {
+        check_assist_not_applicable(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let 1: u32 = v.iter().sum() else$0 { return };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_on_else() {
+        check_assist_not_applicable(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let Ok(x) = f() else {$0 return };
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_no_macropat() {
+        check_assist_not_applicable(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let m!() = g() else$0 { return };
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_target() {
+        check_assist_target(
+            convert_let_else_to_match,
+            r"
+fn main() {
+    let Ok(x) = f() else$0 { continue };
+}",
+            "let Ok(x) = f() else { continue };",
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_basic() {
+        check_assist(
+            convert_let_else_to_match,
+            r"
+fn main() {
+    let Ok(x) = f() else$0 { continue };
+}",
+            r"
+fn main() {
+    let x = match f() {
+        Ok(x) => x,
+        _ => continue,
+    };
+}",
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_const_ref() {
+        check_assist(
+            convert_let_else_to_match,
+            r"
+enum Option<T> {
+    Some(T),
+    None,
+}
+use Option::*;
+fn main() {
+    let None = f() el$0se { continue };
+}",
+            r"
+enum Option<T> {
+    Some(T),
+    None,
+}
+use Option::*;
+fn main() {
+    match f() {
+        None => {}
+        _ => continue,
+    }
+}",
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_const_ref_const() {
+        check_assist(
+            convert_let_else_to_match,
+            r"
+const NEG1: i32 = -1;
+fn main() {
+    let NEG1 = f() el$0se { continue };
+}",
+            r"
+const NEG1: i32 = -1;
+fn main() {
+    match f() {
+        NEG1 => {}
+        _ => continue,
+    }
+}",
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_mut() {
+        check_assist(
+            convert_let_else_to_match,
+            r"
+fn main() {
+    let Ok(mut x) = f() el$0se { continue };
+}",
+            r"
+fn main() {
+    let mut x = match f() {
+        Ok(x) => x,
+        _ => continue,
+    };
+}",
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_multi_binders() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let ControlFlow::Break((x, "tag", y, ..)) = f() else$0 { g(); return };
+}"#,
+            r#"
+fn main() {
+    let (x, y) = match f() {
+        ControlFlow::Break((x, "tag", y, ..)) => (x, y),
+        _ => { g(); return }
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_slice() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let [one, 1001, other] = f() else$0 { break };
+}"#,
+            r#"
+fn main() {
+    let (one, other) = match f() {
+        [one, 1001, other] => (one, other),
+        _ => break,
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_struct() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let [Struct { inner: Some(it) }, 1001, other] = f() else$0 { break };
+}"#,
+            r#"
+fn main() {
+    let (it, other) = match f() {
+        [Struct { inner: Some(it) }, 1001, other] => (it, other),
+        _ => break,
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_struct_ident_pat() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let [Struct { inner }, 1001, other] = f() else$0 { break };
+}"#,
+            r#"
+fn main() {
+    let (inner, other) = match f() {
+        [Struct { inner }, 1001, other] => (inner, other),
+        _ => break,
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_no_binder() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let (8 | 9) = f() else$0 { panic!() };
+}"#,
+            r#"
+fn main() {
+    match f() {
+        (8 | 9) => {}
+        _ => panic!(),
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_range() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let 1.. = f() e$0lse { return };
+}"#,
+            r#"
+fn main() {
+    match f() {
+        1.. => {}
+        _ => return,
+    }
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_refpat() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let Ok(&mut x) = f(&mut 0) else$0 { return };
+}"#,
+            r#"
+fn main() {
+    let x = match f(&mut 0) {
+        Ok(&mut x) => x,
+        _ => return,
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_refmut() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let Ok(ref mut x) = f() else$0 { return };
+}"#,
+            r#"
+fn main() {
+    let x = match f() {
+        Ok(ref mut x) => x,
+        _ => return,
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_atpat() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let out @ Ok(ins) = f() else$0 { return };
+}"#,
+            r#"
+fn main() {
+    let (out, ins) = match f() {
+        out @ Ok(ins) => (out, ins),
+        _ => return,
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn convert_let_else_to_match_complex_init() {
+        check_assist(
+            convert_let_else_to_match,
+            r#"
+fn main() {
+    let v = vec![1, 2, 3];
+    let &[mut x, y, ..] = &v.iter().collect::<Vec<_>>()[..] else$0 { return };
+}"#,
+            r#"
+fn main() {
+    let v = vec![1, 2, 3];
+    let (mut x, y) = match &v.iter().collect::<Vec<_>>()[..] {
+        &[x, y, ..] => (x, y),
+        _ => return,
+    };
+}"#,
+        );
+    }
+}
diff --git a/crates/ide-assists/src/lib.rs b/crates/ide-assists/src/lib.rs
index c1751e8b406..a5dfb5d2953 100644
--- a/crates/ide-assists/src/lib.rs
+++ b/crates/ide-assists/src/lib.rs
@@ -117,6 +117,7 @@ mod handlers {
     mod convert_integer_literal;
     mod convert_into_to_from;
     mod convert_iter_for_each_to_for;
+    mod convert_let_else_to_match;
     mod convert_tuple_struct_to_named_struct;
     mod convert_to_guarded_return;
     mod convert_while_to_loop;
@@ -206,6 +207,7 @@ mod handlers {
             convert_into_to_from::convert_into_to_from,
             convert_iter_for_each_to_for::convert_iter_for_each_to_for,
             convert_iter_for_each_to_for::convert_for_loop_with_for_each,
+            convert_let_else_to_match::convert_let_else_to_match,
             convert_to_guarded_return::convert_to_guarded_return,
             convert_tuple_struct_to_named_struct::convert_tuple_struct_to_named_struct,
             convert_while_to_loop::convert_while_to_loop,
diff --git a/crates/ide-assists/src/tests/generated.rs b/crates/ide-assists/src/tests/generated.rs
index d3917f6c97c..7772563b838 100644
--- a/crates/ide-assists/src/tests/generated.rs
+++ b/crates/ide-assists/src/tests/generated.rs
@@ -385,6 +385,26 @@ fn main() {
 }
 
 #[test]
+fn doctest_convert_let_else_to_match() {
+    check_doc_test(
+        "convert_let_else_to_match",
+        r#####"
+fn main() {
+    let Ok(mut x) = f() else$0 { return };
+}
+"#####,
+        r#####"
+fn main() {
+    let mut x = match f() {
+        Ok(x) => x,
+        _ => return,
+    };
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_convert_to_guarded_return() {
     check_doc_test(
         "convert_to_guarded_return",