ptrCast gives compile error for increasing alignment

See #37

3 files changed, 22 insertions, 2 deletions

diff --git a/test/cases/align.zig b/test/cases/align.zig
index 383d0389b5..ee68408226 100644
--- a/test/cases/align.zig
+++ b/test/cases/align.zig
@@ -53,3 +53,12 @@ test "implicitly decreasing slice alignment" {
     assert(addUnalignedSlice((&a)[0..1], (&b)[0..1]) == 7);
 }
 fn addUnalignedSlice(a: []align 1 const u32, b: []align 1 const u32) -> u32 { a[0] + b[0] }
+
+test "specifying alignment allows pointer cast" {
+    testBytesAlign(0x33);
+}
+fn testBytesAlign(b: u8) {
+    var bytes align 4 = []u8{b, b, b, b};
+    const ptr = @ptrCast(&u32, &bytes[0]);
+    assert(*ptr == 0x33333333);
+}
diff --git a/test/compare_output.zig b/test/compare_output.zig
index bf2255881b..39318c31a0 100644
--- a/test/compare_output.zig
+++ b/test/compare_output.zig
@@ -262,8 +262,8 @@ pub fn addCases(cases: &tests.CompareOutputContext) {
         \\const c = @cImport(@cInclude("stdlib.h"));
         \\
         \\export fn compare_fn(a: ?&const c_void, b: ?&const c_void) -> c_int {
-        \\    const a_int = @ptrCast(&i32, a ?? unreachable);
-        \\    const b_int = @ptrCast(&i32, b ?? unreachable);
+        \\    const a_int = @ptrCast(&align 1 i32, a ?? unreachable);
+        \\    const b_int = @ptrCast(&align 1 i32, b ?? unreachable);
         \\    if (*a_int < *b_int) {
         \\        -1
         \\    } else if (*a_int > *b_int) {
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index 03110f98e7..96898d1744 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -2011,4 +2011,15 @@ pub fn addCases(cases: &tests.CompileErrorContext) {
         \\}
     ,
         ".tmp_source.zig:9:17: error: expected type '[]u32', found '[]align 1 u32'");
+
+    cases.add("increase pointer alignment in @ptrCast",
+        \\export fn entry() -> u32 {
+        \\    var bytes: [4]u8 align 4 = []u8{0x01, 0x02, 0x03, 0x04};
+        \\    const ptr = @ptrCast(&u32, &bytes[0]);
+        \\    return *ptr;
+        \\}
+    ,
+        ".tmp_source.zig:3:17: error: cast increases pointer alignment",
+        ".tmp_source.zig:3:38: note: '&u8' has alignment 1",
+        ".tmp_source.zig:3:27: note: '&u32' has alignment 4");
 }