Fix the type of props.theme for StyledComponent without AdditionalP…

…rops (#1708)

* Fix Theme type

* Add unit test for theme type

* Extract the Theme test in a separate test

* Add changeset

* Better changeset

Co-Authored-By: Mateusz Burzyński <mateuszburzynski@gmail.com>

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

.changeset/tasty-goats-crash.md

@@ -0,0 +1,5 @@
+---
+'@emotion/styled': patch
+---
+
+Fix `props.theme` type in styled component interpolation being optional (`Theme | undefined`) for components without `AdditionalProps` being specified.

packages/styled/types/base.d.ts

@@ -68,7 +68,9 @@ export interface CreateStyledComponent<
 
   (
     template: TemplateStringsArray,
-    ...styles: Array<Interpolation<ComponentProps & SpecificComponentProps>>
+    ...styles: Array<
+      Interpolation<ComponentProps & SpecificComponentProps & { theme: Theme }>
+    >
   ): StyledComponent<ComponentProps, SpecificComponentProps>
 
   /**

packages/styled/types/tests.tsx

@@ -112,6 +112,9 @@ const Input4 = styled.input<AdditionalTest>`
   marginLeft: props.left
 })}
 `
+const Input5 = styled.input`
+  color: ${props => props.theme.primary};
+`
 ;<Input
   onChange={(evt: React.ChangeEvent<HTMLInputElement>) =>
     console.log(evt.target.value)