[vala/staging] vala: SliceExpression need to return heap-allocated or unowned references

[Rico Tzschichholz <ricotz src gnome org>]

commit 462fdc23f804fe7c5d355c3c593ace7303eb15a4
Author: Ulrich Küttler <kuettler gmail com>
Date:   Tue Dec 22 08:59:16 2020 +0100

    vala: SliceExpression need to return heap-allocated or unowned references
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/1120

 tests/Makefile.am                    |  1 +
 tests/arrays/slice-fixed-length.vala | 75 ++++++++++++++++++++++++++++++++++++
 vala/valasliceexpression.vala        |  7 ++++
 3 files changed, 83 insertions(+)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index ddac20684..e4a305f21 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -128,6 +128,7 @@ TESTS = \
        arrays/resize-unowned-invalid.test \
        arrays/resize-unowned-invalid-2.test \
        arrays/resize-unowned-invalid-3.test \
+       arrays/slice-fixed-length.vala \
        arrays/slice-invalid-start.test \
        arrays/slice-invalid-stop.test \
        arrays/slice-no-array.test \
diff --git a/tests/arrays/slice-fixed-length.vala b/tests/arrays/slice-fixed-length.vala
new file mode 100644
index 000000000..7b81f615a
--- /dev/null
+++ b/tests/arrays/slice-fixed-length.vala
@@ -0,0 +1,75 @@
+void manam (string[] foo) {
+       assert (foo.length == 2);
+       assert (foo[0] == "bar");
+       assert (foo[1] == "baz");
+}
+
+void minim (owned string[] foo) {
+       assert (foo.length == 2);
+       assert (foo[0] == "bar");
+       assert (foo[1] == "baz");
+}
+
+void main () {
+       string bar[4] = { "foo", "bar", "baz", "buzz" };
+       {
+               var foo = bar[1:3];
+               assert (foo.length == 2);
+               assert (foo[0] == "bar");
+               assert (foo[1] == "baz");
+       }
+       {
+               unowned var foo = bar[1:3];
+               assert (foo.length == 2);
+               assert (foo[0] == "bar");
+               assert (foo[1] == "baz");
+       }
+       {
+               int begin = 1;
+               var foo = bar[begin:3];
+               assert (foo.length == 2);
+               assert (foo[0] == "bar");
+               assert (foo[1] == "baz");
+       }
+       {
+               string[] foo = bar[1:3];
+               assert (foo.length == 2);
+               assert (foo[0] == "bar");
+               assert (foo[1] == "baz");
+       }
+       {
+               unowned string[] foo = bar[1:3];
+               assert (foo.length == 2);
+               assert (foo[0] == "bar");
+               assert (foo[1] == "baz");
+       }
+       {
+               int end = 3;
+               string[] foo = bar[1:end];
+               assert (foo.length == 2);
+               assert (foo[0] == "bar");
+               assert (foo[1] == "baz");
+       }
+       {
+               manam (bar[1:3]);
+       }
+       {
+               int begin = 1;
+               manam (bar[begin:3]);
+       }
+       {
+               int end = 3;
+               manam (bar[1:end]);
+       }
+       {
+               minim (bar[1:3]);
+       }
+       {
+               int begin = 1;
+               minim (bar[begin:3]);
+       }
+       {
+               int end = 3;
+               minim (bar[1:end]);
+       }
+}
diff --git a/vala/valasliceexpression.vala b/vala/valasliceexpression.vala
index 8eca80998..a9502b3e8 100644
--- a/vala/valasliceexpression.vala
+++ b/vala/valasliceexpression.vala
@@ -147,6 +147,13 @@ public class Vala.SliceExpression : Expression {
                if (container.value_type is ArrayType) {
                        value_type = container.value_type.copy ();
                        value_type.value_owned = false;
+
+                       // inline allocated results are not compatible with non-constant start/stop 
expressions
+                       unowned ArrayType array_type = (ArrayType) value_type;
+                       array_type.fixed_length = false;
+                       array_type.inline_allocated = false;
+                       array_type.length = null;
+
                        value_type.check (context);
 
                        /* check if the index is of type integer */