[red-knot] Statically known branches

Author: sharkdp

crates/red_knot_python_semantic/resources/mdtest/boolean/short_circuit.md

@@ -38,7 +38,7 @@ if (x := 1) and bool_instance():
 if True or (x := 1):
     # TODO: infer that the second arm is never executed, and raise `unresolved-reference`.
     # error: [possibly-unresolved-reference]
-    reveal_type(x)  # revealed: Literal[1]
+    reveal_type(x)  # revealed: Never
 
 if True and (x := 1):
     # TODO: infer that the second arm is always executed, do not raise a diagnostic

crates/red_knot_python_semantic/resources/mdtest/statically-known-branches.md

@@ -0,0 +1,294 @@
+# Statically-known branches
+
+## Always false
+
+### If
+
+```py
+x = 1
+
+if False:
+    x = 2
+
+reveal_type(x)  # revealed: Literal[1]
+```
+
+### Else
+
+```py
+x = 1
+
+if True:
+    pass
+else:
+    x = 2
+
+reveal_type(x)  # revealed: Literal[1]
+```
+
+## Always true
+
+### If
+
+```py
+x = 1
+
+if True:
+    x = 2
+
+reveal_type(x)  # revealed: Literal[2]
+```
+
+### Else
+
+```py
+x = 1
+
+if False:
+    pass
+else:
+    x = 2
+
+reveal_type(x)  # revealed: Literal[2]
+```
+
+## Combination
+
+```py
+x = 1
+
+if True:
+    x = 2
+else:
+    x = 3
+
+reveal_type(x)  # revealed: Literal[2]
+```
+
+## Nested
+
+```py path=nested_if_true_if_true.py
+x = 1
+
+if True:
+    if True:
+        x = 2
+    else:
+        x = 3
+else:
+    x = 4
+
+reveal_type(x)  # revealed: Literal[2]
+```
+
+```py path=nested_if_true_if_false.py
+x = 1
+
+if True:
+    if False:
+        x = 2
+    else:
+        x = 3
+else:
+    x = 4
+
+reveal_type(x)  # revealed: Literal[3]
+```
+
+```py path=nested_if_true_if_bool.py
+def flag() -> bool: ...
+
+x = 1
+
+if True:
+    if flag():
+        x = 2
+    else:
+        x = 3
+else:
+    x = 4
+
+reveal_type(x)  # revealed: Literal[2, 3]
+```
+
+```py path=nested_if_bool_if_true.py
+def flag() -> bool: ...
+
+x = 1
+
+if flag():
+    if True:
+        x = 2
+    else:
+        x = 3
+else:
+    x = 4
+
+reveal_type(x)  # revealed: Literal[2, 4]
+```
+
+```py path=nested_else_if_true.py
+x = 1
+
+if False:
+    x = 2
+else:
+    if True:
+        x = 3
+    else:
+        x = 4
+
+reveal_type(x)  # revealed: Literal[3]
+```
+
+```py path=nested_else_if_false.py
+x = 1
+
+if False:
+    x = 2
+else:
+    if False:
+        x = 3
+    else:
+        x = 4
+
+reveal_type(x)  # revealed: Literal[4]
+```
+
+```py path=nested_else_if_bool.py
+def flag() -> bool: ...
+
+x = 1
+
+if False:
+    x = 2
+else:
+    if flag():
+        x = 3
+    else:
+        x = 4
+
+reveal_type(x)  # revealed: Literal[3, 4]
+```
+
+## If-expressions
+
+### Always true
+
+```py
+x = 1 if True else 2
+
+reveal_type(x)  # revealed: Literal[1]
+```
+
+### Always false
+
+```py
+x = 1 if False else 2
+
+reveal_type(x)  # revealed: Literal[2]
+```
+
+## Boolean expressions
+
+### Always true
+
+```py
+(x := 1) == 1 or (x := 2)
+
+reveal_type(x)  # revealed: Literal[1]
+```
+
+### Always false
+
+```py
+(x := 1) == 0 or (x := 2)
+
+reveal_type(x)  # revealed: Literal[2]
+```
+
+## Conditional declarations
+
+```py path=if_false.py
+x: str
+
+if False:
+    x: int
+
+def f() -> None:
+    reveal_type(x)  # revealed: str
+```
+
+```py path=if_true_else.py
+x: str
+
+if True:
+    pass
+else:
+    x: int
+
+def f() -> None:
+    reveal_type(x)  # revealed: str
+```
+
+```py path=if_true.py
+x: str
+
+if True:
+    x: int
+
+def f() -> None:
+    reveal_type(x)  # revealed: int
+```
+
+```py path=if_false_else.py
+x: str
+
+if False:
+    pass
+else:
+    x: int
+
+def f() -> None:
+    reveal_type(x)  # revealed: int
+```
+
+```py path=if_bool.py
+def flag() -> bool: ...
+
+x: str
+
+if flag():
+    x: int
+
+def f() -> None:
+    reveal_type(x)  # revealed: str | int
+```
+
+## Conditionally defined functions
+
+```py
+def f() -> int: ...
+def g() -> int: ...
+
+if True:
+    def f() -> str: ...
+
+else:
+    def g() -> str: ...
+
+reveal_type(f())  # revealed: str
+reveal_type(g())  # revealed: int
+```
+
+## Conditionally defined class attributes
+
+```py
+class C:
+    if True:
+        x: int = 1
+    else:
+        x: str = "a"
+
+reveal_type(C.x)  # revealed: int
+```

crates/red_knot_python_semantic/resources/mdtest/sys_version_info.md

@@ -49,14 +49,14 @@ sometimes not:
 ```py
 import sys
 
-reveal_type(sys.version_info >= (3, 9, 1))  # revealed: bool
-reveal_type(sys.version_info >= (3, 9, 1, "final", 0))  # revealed: bool
+reveal_type(sys.version_info >= (3, 9, 1))  # revealed: Literal[True]
+reveal_type(sys.version_info >= (3, 9, 1, "final", 0))  # revealed: Literal[True]
 
 # TODO: While this won't fail at runtime, the user has probably made a mistake
 # if they're comparing a tuple of length >5 with `sys.version_info`
 # (`sys.version_info` is a tuple of length 5). It might be worth
 # emitting a lint diagnostic of some kind warning them about the probable error?
-reveal_type(sys.version_info >= (3, 9, 1, "final", 0, 5))  # revealed: bool
+reveal_type(sys.version_info >= (3, 9, 1, "final", 0, 5))  # revealed: Literal[True]
 
 reveal_type(sys.version_info == (3, 8, 1, "finallllll", 0))  # revealed: Literal[False]
 ```
@@ -102,8 +102,8 @@ The fields of `sys.version_info` can be accessed by name:
 import sys
 
 reveal_type(sys.version_info.major >= 3)  # revealed: Literal[True]
-reveal_type(sys.version_info.minor >= 9)  # revealed: Literal[True]
-reveal_type(sys.version_info.minor >= 10)  # revealed: Literal[False]
+reveal_type(sys.version_info.minor >= 12)  # revealed: Literal[True]
+reveal_type(sys.version_info.minor >= 13)  # revealed: Literal[False]
 ```
 
 But the `micro`, `releaselevel` and `serial` fields are inferred as `@Todo` until we support
@@ -125,14 +125,14 @@ The fields of `sys.version_info` can be accessed by index or by slice:
 import sys
 
 reveal_type(sys.version_info[0] < 3)  # revealed: Literal[False]
-reveal_type(sys.version_info[1] > 9)  # revealed: Literal[False]
+reveal_type(sys.version_info[1] > 13)  # revealed: Literal[False]
 
-# revealed: tuple[Literal[3], Literal[9], int, Literal["alpha", "beta", "candidate", "final"], int]
+# revealed: tuple[Literal[3], Literal[12], int, Literal["alpha", "beta", "candidate", "final"], int]
 reveal_type(sys.version_info[:5])
 
-reveal_type(sys.version_info[:2] >= (3, 9))  # revealed: Literal[True]
-reveal_type(sys.version_info[0:2] >= (3, 10))  # revealed: Literal[False]
-reveal_type(sys.version_info[:3] >= (3, 10, 1))  # revealed: Literal[False]
+reveal_type(sys.version_info[:2] >= (3, 12))  # revealed: Literal[True]
+reveal_type(sys.version_info[0:2] >= (3, 13))  # revealed: Literal[False]
+reveal_type(sys.version_info[:3] >= (3, 13, 1))  # revealed: Literal[False]
 reveal_type(sys.version_info[3] == "final")  # revealed: bool
 reveal_type(sys.version_info[3] == "finalllllll")  # revealed: Literal[False]
 ```

crates/red_knot_python_semantic/src/semantic_index.rs

@@ -1229,4 +1229,32 @@ match 1:
 
         assert!(matches!(binding.kind(&db), DefinitionKind::For(_)));
     }
+
+    #[test]
+    #[ignore]
+    fn if_statement() {
+        let TestCase { db, file } = test_case(
+            "
+x = False
+
+if True:
+    x: bool
+",
+        );
+
+        let index = semantic_index(&db, file);
+        // let global_table = index.symbol_table(FileScopeId::global());
+
+        let use_def = index.use_def_map(FileScopeId::global());
+
+        // use_def
+
+        use_def.print(&db);
+
+        panic!();
+        // let binding = use_def
+        //     .first_public_binding(global_table.symbol_id_by_name(name).expect("symbol exists"))
+        //     .expect("Expected with item definition for {name}");
+        // assert!(matches!(binding.kind(&db), DefinitionKind::WithItem(_)));
+    }
 }