Merge pull request #16042 from mlugg/fix/slice-len-comptime-mutation

Fix comptime mutation of slice len

Author: andrewrk

src/Sema.zig

@@ -10069,7 +10069,7 @@ fn zirSliceSentinel(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileErr
     const extra = sema.code.extraData(Zir.Inst.SliceSentinel, inst_data.payload_index).data;
     const array_ptr = try sema.resolveInst(extra.lhs);
     const start = try sema.resolveInst(extra.start);
-    const end = try sema.resolveInst(extra.end);
+    const end: Air.Inst.Ref = if (extra.end == .none) .none else try sema.resolveInst(extra.end);
     const sentinel = try sema.resolveInst(extra.sentinel);
     const ptr_src: LazySrcLoc = .{ .node_offset_slice_ptr = inst_data.src_node };
     const start_src: LazySrcLoc = .{ .node_offset_slice_start = inst_data.src_node };
@@ -29280,7 +29280,7 @@ fn beginComptimePtrLoad(
                         },
                         Value.slice_len_index => TypedValue{
                             .ty = Type.usize,
-                            .val = mod.intern_pool.indexToKey(tv.val.toIntern()).ptr.len.toValue(),
+                            .val = mod.intern_pool.indexToKey(try tv.val.intern(tv.ty, mod)).ptr.len.toValue(),
                         },
                         else => unreachable,
                     };

test/behavior/slice.zig

@@ -378,12 +378,16 @@ test "slice syntax resulting in pointer-to-array" {
             try testPointer0();
             try testPointerAlign();
             try testSlice();
+            try testSliceZ();
             try testSliceOpt();
             try testSliceAlign();
+            try testConcatStrLiterals();
             try testSliceLength();
             try testSliceLengthZ();
             try testArrayLength();
             try testArrayLengthZ();
+            try testMultiPointer();
+            try testMultiPointerLengthZ();
         }
 
         fn testArray() !void {
@@ -469,8 +473,12 @@ test "slice syntax resulting in pointer-to-array" {
             var array = [5:0]u8{ 1, 2, 3, 4, 5 };
             var slice: [:0]u8 = &array;
             try comptime expect(@TypeOf(slice[1..3]) == *[2]u8);
-            try comptime expect(@TypeOf(slice[1..]) == [:0]u8);
             try comptime expect(@TypeOf(slice[1..3 :4]) == *[2:4]u8);
+            if (@inComptime()) {
+                try comptime expect(@TypeOf(slice[1..]) == *[4:0]u8);
+            } else {
+                try comptime expect(@TypeOf(slice[1..]) == [:0]u8);
+            }
         }
 
         fn testSliceOpt() !void {
@@ -491,8 +499,8 @@ test "slice syntax resulting in pointer-to-array" {
         }
 
         fn testConcatStrLiterals() !void {
-            try expectEqualSlices("a"[0..] ++ "b"[0..], "ab");
-            try expectEqualSlices("a"[0.. :0] ++ "b"[0.. :0], "ab");
+            try expectEqualSlices(u8, "ab", "a"[0..] ++ "b"[0..]);
+            try expectEqualSlices(u8, "ab", "a"[0.. :0] ++ "b"[0.. :0]);
         }
 
         fn testSliceLength() !void {
@@ -541,18 +549,18 @@ test "slice syntax resulting in pointer-to-array" {
             var array = [5:0]u8{ 1, 2, 3, 4, 5 };
             var ptr: [*]u8 = &array;
             try comptime expect(@TypeOf(ptr[1..][0..2]) == *[2]u8);
-            try comptime expect(@TypeOf(ptr[1..][0..4]) == *[4:0]u8);
+            try comptime expect(@TypeOf(ptr[1..][0..4]) == *[4]u8);
             try comptime expect(@TypeOf(ptr[1..][0..2 :4]) == *[2:4]u8);
             try comptime expect(@TypeOf(ptr[1.. :0][0..2]) == *[2]u8);
-            try comptime expect(@TypeOf(ptr[1.. :0][0..4]) == *[4:0]u8);
+            try comptime expect(@TypeOf(ptr[1.. :0][0..4]) == *[4]u8);
             try comptime expect(@TypeOf(ptr[1.. :0][0..2 :4]) == *[2:4]u8);
 
             var ptr_z: [*:0]u8 = &array;
             try comptime expect(@TypeOf(ptr_z[1..][0..2]) == *[2]u8);
-            try comptime expect(@TypeOf(ptr_z[1..][0..4]) == *[4:0]u8);
+            try comptime expect(@TypeOf(ptr_z[1..][0..4]) == *[4]u8);
             try comptime expect(@TypeOf(ptr_z[1..][0..2 :4]) == *[2:4]u8);
             try comptime expect(@TypeOf(ptr_z[1.. :0][0..2]) == *[2]u8);
-            try comptime expect(@TypeOf(ptr_z[1.. :0][0..4]) == *[4:0]u8);
+            try comptime expect(@TypeOf(ptr_z[1.. :0][0..4]) == *[4]u8);
             try comptime expect(@TypeOf(ptr_z[1.. :0][0..2 :4]) == *[2:4]u8);
         }
     };
@@ -869,3 +877,20 @@ test "write through pointer to optional slice arg" {
     try S.bar(&foo);
     try expectEqualStrings(foo.?, "ok");
 }
+
+test "modify slice length at comptime" {
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
+
+    const arr: [2]u8 = .{ 10, 20 };
+    comptime var s: []const u8 = arr[0..0];
+    s.len += 1;
+    const a = s;
+    s.len += 1;
+    const b = s;
+
+    try expectEqualSlices(u8, &.{10}, a);
+    try expectEqualSlices(u8, &.{ 10, 20 }, b);
+}