[vala/0.40] vala: SliceExpression need to return heap-allocated or unowned references

[Rico Tzschichholz <ricotz src gnome org>]

commit c47dead3444bbd1327aa6eda78eda8687c0eeb56
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 | 69 ++++++++++++++++++++++++++++++++++++
 vala/valasliceexpression.vala        |  6 ++++
 3 files changed, 76 insertions(+)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index bd8f62d7e..669dccecb 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -101,6 +101,7 @@ 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..21e9c6d28
--- /dev/null
+++ b/tests/arrays/slice-fixed-length.vala
@@ -0,0 +1,69 @@
+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 string[] 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");
+       }
+       {
+               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 bc399c8fc..0a4110e17 100644
--- a/vala/valasliceexpression.vala
+++ b/vala/valasliceexpression.vala
@@ -147,6 +147,12 @@ public class Vala.SliceExpression : Expression {
                        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;
+
                        /* check if the index is of type integer */
                        if (!(start.value_type is IntegerType || start.value_type is EnumValueType)) {
                                error = true;