Use "target()" to parse "when" block

`target()` as used in parsing "let" and "if let" implements parsing
nested tuples and structs. But it does not implement parsing literals.

The functions `match_variant()` and `with_parameters()` as used in
parsing "when" blocks do not implement parsing nested structs, but it
implements parsing literals.

This PR combines `match_variant()` and `with_parameters()` into
`target()`, so that all `{%when%}` support nested structs, too.

5 files changed, 78 insertions, 0 deletions

diff --git a/testing/templates/match-option-result-option.html b/testing/templates/match-option-result-option.html
new file mode 100644
index 0000000..25396b6
--- /dev/null
+++ b/testing/templates/match-option-result-option.html
@@ -0,0 +1,10 @@
+{%- match foo -%}
+    {%- when None -%}
+        nothing
+    {%- when Some(Err(err)) -%}
+        err={{err}}
+    {%- when Some(Ok(None)) -%}
+        num=absent
+    {%- when Some(Ok(Some(num))) -%}
+        num={{num}}
+{%- endmatch -%}
diff --git a/testing/tests/matches.rs b/testing/tests/matches.rs
index 380a69c..c328e39 100644
--- a/testing/tests/matches.rs
+++ b/testing/tests/matches.rs
@@ -130,3 +130,27 @@ fn test_match_without_with_keyword() {
     let s = MatchWithoutWithKeyword { foo: None };
     assert_eq!(s.render().unwrap(), "");
 }
+
+#[derive(Template)]
+#[template(path = "match-option-result-option.html")]
+struct MatchOptionResultOption {
+    foo: Option<Result<Option<usize>, &'static str>>,
+}
+
+#[test]
+fn test_match_option_result_option() {
+    let s = MatchOptionResultOption { foo: None };
+    assert_eq!(s.render().unwrap(), "nothing");
+    let s = MatchOptionResultOption {
+        foo: Some(Err("fail")),
+    };
+    assert_eq!(s.render().unwrap(), "err=fail");
+    let s = MatchOptionResultOption {
+        foo: Some(Ok(None)),
+    };
+    assert_eq!(s.render().unwrap(), "num=absent");
+    let s = MatchOptionResultOption {
+        foo: Some(Ok(Some(4711))),
+    };
+    assert_eq!(s.render().unwrap(), "num=4711");
+}
diff --git a/testing/tests/ui/lit_on_assignment_lhs.rs b/testing/tests/ui/lit_on_assignment_lhs.rs
new file mode 100644
index 0000000..1793770
--- /dev/null
+++ b/testing/tests/ui/lit_on_assignment_lhs.rs
@@ -0,0 +1,11 @@
+use askama::Template;
+
+#[derive(Template)]
+#[template(
+    source = "{%let 7=x%}",
+    ext = "txt"
+)]
+struct MyTemplate;
+
+fn main() {
+}
diff --git a/testing/tests/ui/lit_on_assignment_lhs.stderr b/testing/tests/ui/lit_on_assignment_lhs.stderr
new file mode 100644
index 0000000..fa488cb
--- /dev/null
+++ b/testing/tests/ui/lit_on_assignment_lhs.stderr
@@ -0,0 +1,7 @@
+error: proc-macro derive panicked
+ --> $DIR/lit_on_assignment_lhs.rs:3:10
+  |
+3 | #[derive(Template)]
+  |          ^^^^^^^^
+  |
+  = help: message: Cannot have literals on the left-hand-side of an assignment.
diff --git a/testing/tests/vars.rs b/testing/tests/vars.rs
index 75d10e5..5447351 100644
--- a/testing/tests/vars.rs
+++ b/testing/tests/vars.rs
@@ -105,3 +105,29 @@ fn test_destruct_tuple() {
     };
     assert_eq!(t.render().unwrap(), "wxyz\nwz\nw");
 }
+
+#[derive(Template)]
+#[template(
+    source = "{% let x = 1 %}{% for x in x..=x %}{{ x }}{% endfor %}",
+    ext = "txt"
+)]
+struct DeclRange;
+
+#[test]
+fn test_decl_range() {
+    let t = DeclRange;
+    assert_eq!(t.render().unwrap(), "1");
+}
+
+#[derive(Template)]
+#[template(
+    source = "{% let x %}{% let x = 1 %}{% for x in x..=x %}{{ x }}{% endfor %}",
+    ext = "txt"
+)]
+struct DeclAssignRange;
+
+#[test]
+fn test_decl_assign_range() {
+    let t = DeclAssignRange;
+    assert_eq!(t.render().unwrap(), "1");
+}