name resolution for guard patterns

2 files changed, 214 insertions, 0 deletions

diff --git a/tests/ui/pattern/rfc-3637-guard-patterns/name-resolution.rs b/tests/ui/pattern/rfc-3637-guard-patterns/name-resolution.rs
new file mode 100644
index 00000000000..83ad8c76bb1
--- /dev/null
+++ b/tests/ui/pattern/rfc-3637-guard-patterns/name-resolution.rs
@@ -0,0 +1,81 @@
+//! Test that guard patterns can see bindings already in scope and bindings introduced in their
+//! subpattern, but no other bindings from the containing pattern. Also make sure bindings
+//! introduced in guard patterns are visible in fn/arm/loop/etc bodies.
+
+#![feature(guard_patterns)]
+#![expect(incomplete_features)]
+
+fn good_fn_item(((x if x) | x): bool) -> bool { x }
+
+fn bad_fn_item_1(x: bool, ((y if x) | y): bool) {}
+//~^ ERROR cannot find value `x` in this scope
+fn bad_fn_item_2(((x if y) | x): bool, y: bool) {}
+//~^ ERROR cannot find value `y` in this scope
+
+fn main() {
+    let ((local if local) if local) = false;
+
+    match (true, true) {
+        (x if local, y if good_fn_item(y)) => x && y,
+        (x, y if x) => x && y,
+        //~^ ERROR cannot find value `x` in this scope
+        (x if y, y) => x && y,
+        //~^ ERROR cannot find value `y` in this scope
+    };
+
+    match (true,) {
+        (x @ y if x && y,) => x && y,
+        (x @ (y if y),) => x && y,
+        (x @ (y if x),) => x && y,
+        //~^ ERROR cannot find value `x` in this scope
+    };
+
+    match (Ok(true),) {
+        ((Ok(x) | Err(x)) if good_fn_item(x),) => x,
+        ((Ok(x) if local) | (Err(x) if good_fn_item(x)),) => x,
+        ((Ok(x if x) if x) | (Err(x if x) if x) if x,) if x => x,
+        ((Ok(x) if y) | (Err(y) if x),) => x && y,
+        //~^ ERROR variable `x` is not bound in all patterns
+        //~| ERROR variable `y` is not bound in all patterns
+        //~| ERROR cannot find value `x` in this scope
+        //~| ERROR cannot find value `y` in this scope
+    };
+
+    let (_ if nonexistent) = true;
+    //~^ ERROR cannot find value `nonexistent` in this scope
+    if let ((x, y if x) | (x if y, y)) = (true, true) { x && y; }
+    //~^ ERROR cannot find value `x` in this scope
+    //~| ERROR cannot find value `y` in this scope
+    while let ((x, y if x) | (x if y, y)) = (true, true) { x && y; }
+    //~^ ERROR cannot find value `x` in this scope
+    //~| ERROR cannot find value `y` in this scope
+    for ((x, y if x) | (x if y, y)) in [(true, true)] { x && y; }
+    //~^ ERROR cannot find value `x` in this scope
+    //~| ERROR cannot find value `y` in this scope
+
+    (|(x if x), (y if y)| x && y)(true, true);
+    (|(x if y), (y if x)| x && y)(true, true);
+    //~^ ERROR cannot find value `x` in this scope
+    //~| ERROR cannot find value `y` in this scope
+
+    // FIXME(guard_patterns): mismatched bindings are not yet allowed
+    match Some(0) {
+        Some(x if x > 0) | None => {}
+        //~^ ERROR variable `x` is not bound in all patterns
+    }
+}
+
+/// Make sure shadowing is handled properly. In particular, if a pattern shadows an identifier,
+/// a guard pattern's guard should still see the original binding if the shadowing binding isn't in
+/// its subpattern.
+fn test_shadowing(local: bool) -> u8 {
+    match (0, 0) {
+        // The `local` binding here shadows the `bool` definition, so we get a type error.
+        //~v ERROR mismatched types
+        local if local => 0,
+        // The guards here should see the `bool` definition of `local`, not the new `u8` binding.
+        // The body should see the new binding.
+        (local, _ if local) => local,
+        (_ if local, local) => local,
+    }
+}
diff --git a/tests/ui/pattern/rfc-3637-guard-patterns/name-resolution.stderr b/tests/ui/pattern/rfc-3637-guard-patterns/name-resolution.stderr
new file mode 100644
index 00000000000..d76e60478a1
--- /dev/null
+++ b/tests/ui/pattern/rfc-3637-guard-patterns/name-resolution.stderr
@@ -0,0 +1,133 @@
+error[E0408]: variable `y` is not bound in all patterns
+  --> $DIR/name-resolution.rs:37:10
+   |
+LL |         ((Ok(x) if y) | (Err(y) if x),) => x && y,
+   |          ^^^^^^^^^^^^        - variable not in all patterns
+   |          |
+   |          pattern doesn't bind `y`
+
+error[E0408]: variable `x` is not bound in all patterns
+  --> $DIR/name-resolution.rs:37:25
+   |
+LL |         ((Ok(x) if y) | (Err(y) if x),) => x && y,
+   |              -          ^^^^^^^^^^^^^ pattern doesn't bind `x`
+   |              |
+   |              variable not in all patterns
+
+error[E0408]: variable `x` is not bound in all patterns
+  --> $DIR/name-resolution.rs:63:28
+   |
+LL |         Some(x if x > 0) | None => {}
+   |              -             ^^^^ pattern doesn't bind `x`
+   |              |
+   |              variable not in all patterns
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:10:34
+   |
+LL | fn bad_fn_item_1(x: bool, ((y if x) | y): bool) {}
+   |                                  ^ help: a local variable with a similar name exists: `y`
+
+error[E0425]: cannot find value `y` in this scope
+  --> $DIR/name-resolution.rs:12:25
+   |
+LL | fn bad_fn_item_2(((x if y) | x): bool, y: bool) {}
+   |                         ^ help: a local variable with a similar name exists: `x`
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:20:18
+   |
+LL |         (x, y if x) => x && y,
+   |                  ^ help: a local variable with a similar name exists: `y`
+
+error[E0425]: cannot find value `y` in this scope
+  --> $DIR/name-resolution.rs:22:15
+   |
+LL |         (x if y, y) => x && y,
+   |               ^ help: a local variable with a similar name exists: `x`
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:29:20
+   |
+LL |         (x @ (y if x),) => x && y,
+   |                    ^ help: a local variable with a similar name exists: `y`
+
+error[E0425]: cannot find value `y` in this scope
+  --> $DIR/name-resolution.rs:37:20
+   |
+LL |         ((Ok(x) if y) | (Err(y) if x),) => x && y,
+   |                    ^ help: a local variable with a similar name exists: `x`
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:37:36
+   |
+LL |         ((Ok(x) if y) | (Err(y) if x),) => x && y,
+   |                                    ^ help: a local variable with a similar name exists: `y`
+
+error[E0425]: cannot find value `nonexistent` in this scope
+  --> $DIR/name-resolution.rs:44:15
+   |
+LL |     let (_ if nonexistent) = true;
+   |               ^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:46:22
+   |
+LL |     if let ((x, y if x) | (x if y, y)) = (true, true) { x && y; }
+   |                      ^ help: a local variable with a similar name exists: `y`
+
+error[E0425]: cannot find value `y` in this scope
+  --> $DIR/name-resolution.rs:46:33
+   |
+LL |     if let ((x, y if x) | (x if y, y)) = (true, true) { x && y; }
+   |                                 ^ help: a local variable with a similar name exists: `x`
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:49:25
+   |
+LL |     while let ((x, y if x) | (x if y, y)) = (true, true) { x && y; }
+   |                         ^ help: a local variable with a similar name exists: `y`
+
+error[E0425]: cannot find value `y` in this scope
+  --> $DIR/name-resolution.rs:49:36
+   |
+LL |     while let ((x, y if x) | (x if y, y)) = (true, true) { x && y; }
+   |                                    ^ help: a local variable with a similar name exists: `x`
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:52:19
+   |
+LL |     for ((x, y if x) | (x if y, y)) in [(true, true)] { x && y; }
+   |                   ^ help: a local variable with a similar name exists: `y`
+
+error[E0425]: cannot find value `y` in this scope
+  --> $DIR/name-resolution.rs:52:30
+   |
+LL |     for ((x, y if x) | (x if y, y)) in [(true, true)] { x && y; }
+   |                              ^ help: a local variable with a similar name exists: `x`
+
+error[E0425]: cannot find value `y` in this scope
+  --> $DIR/name-resolution.rs:57:13
+   |
+LL |     (|(x if y), (y if x)| x && y)(true, true);
+   |             ^ help: a local variable with a similar name exists: `x`
+
+error[E0425]: cannot find value `x` in this scope
+  --> $DIR/name-resolution.rs:57:23
+   |
+LL |     (|(x if y), (y if x)| x && y)(true, true);
+   |                       ^ help: a local variable with a similar name exists: `y`
+
+error[E0308]: mismatched types
+  --> $DIR/name-resolution.rs:75:18
+   |
+LL |         local if local => 0,
+   |                  ^^^^^ expected `bool`, found `({integer}, {integer})`
+   |
+   = note: expected type `bool`
+             found tuple `({integer}, {integer})`
+
+error: aborting due to 20 previous errors
+
+Some errors have detailed explanations: E0308, E0408, E0425.
+For more information about an error, try `rustc --explain E0308`.