add Str.contains to builtins

crates/compiler/builtins/roc/Str.roc

@@ -135,6 +135,7 @@ interface Str
         withCapacity,
         withPrefix,
         graphemes,
+        contains,
     ]
     imports [
         Bool.{ Bool, Eq },
@@ -995,3 +996,15 @@ strToNumHelp = \string ->
 ## ```
 withPrefix : Str, Str -> Str
 withPrefix = \str, prefix -> Str.concat prefix str
+
+## Determines whether or not the first Str contains the second.
+## ```
+## expect Str.contains "foobarbaz" "bar"
+## expect !(Str.contains "apple" "orange")
+## expect Str.contains "anything" ""
+## ```
+contains : Str, Str -> Bool
+contains = \haystack, needle ->
+    when firstMatch haystack needle is
+        Some _index -> Bool.true
+        None -> Bool.false

crates/compiler/module/src/symbol.rs

@@ -1346,6 +1346,7 @@ define_builtins! {
         56 STR_IS_VALID_SCALAR: "isValidScalar"
         57 STR_RELEASE_EXCESS_CAPACITY: "releaseExcessCapacity"
         58 STR_WALK_UTF8: "walkUtf8"
+        59 STR_CONTAINS: "contains"
     }
     6 LIST: "List" => {
         0 LIST_LIST: "List" exposed_apply_type=true // the List.List type alias

crates/compiler/test_gen/src/gen_str.rs

@@ -2144,3 +2144,63 @@ fn release_excess_capacity_empty() {
         |value: RocStr| (value.capacity(), value)
     );
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+fn str_contains_positive() {
+    assert_evals_to!(
+        r#"
+        Str.contains "foobarbaz" "bar"
+        "#,
+        true,
+        bool
+    );
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+fn str_contains_negative() {
+    assert_evals_to!(
+        r#"
+        Str.contains "apple" "orange"
+        "#,
+        false,
+        bool
+    );
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+fn str_contains_empty_positive() {
+    assert_evals_to!(
+        r#"
+        Str.contains "anything" ""
+        "#,
+        true,
+        bool
+    );
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+fn str_contains_empty_negative() {
+    assert_evals_to!(
+        r#"
+        Str.contains "" "anything"
+        "#,
+        false,
+        bool
+    );
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+fn str_contains_self() {
+    assert_evals_to!(
+        r#"
+        Str.contains "self" "self"
+        "#,
+        true,
+        bool
+    );
+}