Fix reporting location in aliased types.

Author: oxidase

mypy/types.py

@@ -2920,16 +2920,23 @@ def visit_type_var(self, typ: TypeVarType) -> Type:
         return typ
 
 
+def replace_alias_location(tp: Type, newline: int, newcolumn: int) -> Type:
+    """Set line and column attributes in a generic type and arguments recursively.
+    """
+    tp.line = newline
+    tp.column = newcolumn
+    for ta in getattr(tp, 'args', []):
+        replace_alias_location(ta, newline, newcolumn)
+    return tp
+
+
 def replace_alias_tvars(tp: Type, vars: List[str], subs: List[Type],
                         newline: int, newcolumn: int) -> Type:
     """Replace type variables in a generic type alias tp with substitutions subs
     resetting context. Length of subs should be already checked.
     """
     replacer = InstantiateAliasVisitor(vars, subs)
-    new_tp = tp.accept(replacer)
-    new_tp.line = newline
-    new_tp.column = newcolumn
-    return new_tp
+    return replace_alias_location(tp.accept(replacer), newline, newcolumn)
 
 
 class HasTypeVars(TypeQuery[bool]):

test-data/unit/check-generics.test

@@ -648,6 +648,30 @@ reveal_type(f3()) # N: Revealed type is "Union[builtins.int, __main__.Node[built
 
 [builtins fixtures/list.pyi]
 
+[case testGenericTypeAliasesWithNestedArgs]
+# flags: --pretty --show-error-codes
+import other
+a: other.Array[float]
+reveal_type(a) # N: Revealed type is "other.array[Any, other.dtype[builtins.float]]"
+
+[out]
+main:3: error: Type argument "float" of "dtype" must be a subtype of "generic"  [type-var]
+    a: other.Array[float]
+       ^
+[file other.py]
+from typing import Any, Generic, TypeVar
+
+DT = TypeVar("DT", covariant=True, bound=dtype[Any])
+DTS = TypeVar("DTS", covariant=True, bound=generic)
+S = TypeVar("S", bound=Any)
+ST = TypeVar("ST", bound=generic, covariant=True)
+
+class common: pass
+class generic(common): pass
+class dtype(Generic[DTS]): pass
+class array(common, Generic[S, DT]): pass
+Array = array[Any, dtype[ST]]
+
 [case testGenericTypeAliasesAny]
 from typing import TypeVar, Generic
 T = TypeVar('T')