Commit cfae70ec8e736af3fcd465c78bd80e160968eea8 | zig

author	Robin Voetter <robin@voetter.nl> 2021-08-25 03:44:43+02:00
committer	Andrew Kelley <andrew@ziglang.org> 2021-08-27 18:53:03-04:00
log	cfae70ec8e736af3fcd465c78bd80e160968eea8
tree	04e5925f0ee0d8485644f58ff0f99f492065c232
parent	3aa533519da073695a56a56159b7ea3c487fb1b2

Make slice always return a reference

Previously this returned an rvalue, which leads to unexpected behaviour
when writing expressions such as `x[1..][1..].`

2 files changed, 24 insertions(+), 3 deletions(-)

src
- AstGen.zig
- Zir.zig

src/AstGen.zig+21-3

 @@ -698,7 +698,13 @@ fn expr(gz: *GenZir, scope: *Scope, rl: ResultLoc, node: ast.Node.Index) InnerEr
                 .lhs = lhs,
                 .start = start,
             });
-            return rvalue(gz, rl, result, node);
+            switch (rl) {
+                .ref, .none_or_ref => return result,
+                else => {
+                    const dereffed = try gz.addUnNode(.load, result, node);
+                    return rvalue(gz, rl, dereffed, node);
+                },
+            }
         },
         .slice => {
             const lhs = try expr(gz, scope, .ref, node_datas[node].lhs);
 @@ -710,7 +716,13 @@ fn expr(gz: *GenZir, scope: *Scope, rl: ResultLoc, node: ast.Node.Index) InnerEr
                 .start = start,
                 .end = end,
             });
-            return rvalue(gz, rl, result, node);
+            switch (rl) {
+                .ref, .none_or_ref => return result,
+                else => {
+                    const dereffed = try gz.addUnNode(.load, result, node);
+                    return rvalue(gz, rl, dereffed, node);
+                },
+            }
         },
         .slice_sentinel => {
             const lhs = try expr(gz, scope, .ref, node_datas[node].lhs);
 @@ -724,7 +736,13 @@ fn expr(gz: *GenZir, scope: *Scope, rl: ResultLoc, node: ast.Node.Index) InnerEr
                 .end = end,
                 .sentinel = sentinel,
             });
-            return rvalue(gz, rl, result, node);
+            switch (rl) {
+                .ref, .none_or_ref => return result,
+                else => {
+                    const dereffed = try gz.addUnNode(.load, result, node);
+                    return rvalue(gz, rl, dereffed, node);
+                },
+            }
         },
         .deref => {

src/Zir.zig+3

 @@ -495,12 +495,15 @@ pub const Inst = struct {
         /// Uses the `ptr_type` union field.
         ptr_type,
         /// Slice operation `lhs[rhs..]`. No sentinel and no end offset.
+        /// Returns a pointer to the subslice.
         /// Uses the `pl_node` field. AST node is the slice syntax. Payload is `SliceStart`.
         slice_start,
         /// Slice operation `array_ptr[start..end]`. No sentinel.
+        /// Returns a pointer to the subslice.
         /// Uses the `pl_node` field. AST node is the slice syntax. Payload is `SliceEnd`.
         slice_end,
         /// Slice operation `array_ptr[start..end:sentinel]`.
+        /// Returns a pointer to the subslice.
         /// Uses the `pl_node` field. AST node is the slice syntax. Payload is `SliceSentinel`.
         slice_sentinel,
         /// Write a value to a pointer. For loading, see `load`.