Teach `stubgen` to work with `complex` and unary expressions (#15661)

mypy/stubgen.py

diff --git a/mypy/stubgen.py b/mypy/stubgen.py
index e7fa65d..9084da2 100755
--- a/mypy/stubgen.py
+++ b/mypy/stubgen.py
@@ -80,6 +80,7 @@
     CallExpr,
     ClassDef,
     ComparisonExpr,
+    ComplexExpr,
     Decorator,
     DictExpr,
     EllipsisExpr,
@@ -1396,6 +1397,8 @@
     def get_str_type_of_node(
         self, rvalue: Expression, can_infer_optional: bool = False, can_be_any: bool = True
     ) -> str:
+        rvalue = self.maybe_unwrap_unary_expr(rvalue)
+
         if isinstance(rvalue, IntExpr):
             return "int"
         if isinstance(rvalue, StrExpr):
@@ -1404,8 +1407,13 @@
             return "bytes"
         if isinstance(rvalue, FloatExpr):
             return "float"
-        if isinstance(rvalue, UnaryExpr) and isinstance(rvalue.expr, IntExpr):
-            return "int"
+        if isinstance(rvalue, ComplexExpr):  # 1j
+            return "complex"
+        if isinstance(rvalue, OpExpr) and rvalue.op in ("-", "+"):  # -1j + 1
+            if isinstance(self.maybe_unwrap_unary_expr(rvalue.left), ComplexExpr) or isinstance(
+                self.maybe_unwrap_unary_expr(rvalue.right), ComplexExpr
+            ):
+                return "complex"
         if isinstance(rvalue, NameExpr) and rvalue.name in ("True", "False"):
             return "bool"
         if can_infer_optional and isinstance(rvalue, NameExpr) and rvalue.name == "None":
@@ -1417,6 +1425,40 @@
         else:
             return ""
 
+    def maybe_unwrap_unary_expr(self, expr: Expression) -> Expression:
+        """Unwrap (possibly nested) unary expressions.
+
+        But, some unary expressions can change the type of expression.
+        While we want to preserve it. For example, `~True` is `int`.
+        So, we only allow a subset of unary expressions to be unwrapped.
+        """
+        if not isinstance(expr, UnaryExpr):
+            return expr
+
+        # First, try to unwrap `[+-]+ (int|float|complex)` expr:
+        math_ops = ("+", "-")
+        if expr.op in math_ops:
+            while isinstance(expr, UnaryExpr):
+                if expr.op not in math_ops or not isinstance(
+                    expr.expr, (IntExpr, FloatExpr, ComplexExpr, UnaryExpr)
+                ):
+                    break
+                expr = expr.expr
+            return expr
+
+        # Next, try `not bool` expr:
+        if expr.op == "not":
+            while isinstance(expr, UnaryExpr):
+                if expr.op != "not" or not isinstance(expr.expr, (NameExpr, UnaryExpr)):
+                    break
+                if isinstance(expr.expr, NameExpr) and expr.expr.name not in ("True", "False"):
+                    break
+                expr = expr.expr
+            return expr
+
+        # This is some other unary expr, we cannot do anything with it (yet?).
+        return expr
+
     def print_annotation(self, t: Type) -> str:
         printer = AnnotationPrinter(self)
         return t.accept(printer)

test-data/unit/stubgen.test

diff --git a/test-data/unit/stubgen.test b/test-data/unit/stubgen.test
index 9c7221e..b387aa8 100644
--- a/test-data/unit/stubgen.test
+++ b/test-data/unit/stubgen.test
@@ -127,10 +127,52 @@
 
 def g() -> None: ...
 
-[case testVariable]
-x = 1
+[case testVariables]
+i = 1
+s = 'a'
+f = 1.5
+c1 = 1j
+c2 = 0j + 1
+bl1 = True
+bl2 = False
+bts = b''
 [out]
-x: int
+i: int
+s: str
+f: float
+c1: complex
+c2: complex
+bl1: bool
+bl2: bool
+bts: bytes
+
+[case testVariablesWithUnary]
+i = +-1
+f = -1.5
+c1 = -1j
+c2 = -1j + 1
+bl1 = not True
+bl2 = not not False
+[out]
+i: int
+f: float
+c1: complex
+c2: complex
+bl1: bool
+bl2: bool
+
+[case testVariablesWithUnaryWrong]
+i = not +1
+bl1 = -True
+bl2 = not -False
+bl3 = -(not False)
+[out]
+from _typeshed import Incomplete
+
+i: Incomplete
+bl1: Incomplete
+bl2: Incomplete
+bl3: Incomplete
 
 [case testAnnotatedVariable]
 x: int = 1