Sema: rework peer type logic for pointers

Now it's centered around a switch on the chosen type tag which gives us
easy access to pointer data.

The logic is simplied and in some cases logic is removed when it is
sufficient to choose the type that is a better coercion target without
knowing whether such coercion will succeed ahead of time.

A bug is fixed at the bottom of the function; we were doing the opposite
of what we were supposed to with `seen_const`.

Also the bottom of the function has a more complete handling of the
possible combinations of `any_are_null`, `convert_to_slice`, and
`err_set_ty`.

In the behavior tests, not as many backends needed to be skipped.

1 files changed, 4 insertions, 16 deletions

diff --git a/test/behavior/pointers.zig b/test/behavior/pointers.zig
index 288be7f77e..dc46eeeca8 100644
--- a/test/behavior/pointers.zig
+++ b/test/behavior/pointers.zig
@@ -128,12 +128,6 @@ fn testDerefPtrOneVal() !void {
 }
 
 test "peer type resolution with C pointers" {
-    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
-    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
-
     var ptr_one: *u8 = undefined;
     var ptr_many: [*]u8 = undefined;
     var ptr_c: [*c]u8 = undefined;
@@ -163,11 +157,11 @@ test "implicit casting between C pointer and optional non-C pointer" {
 }
 
 test "implicit cast error unions with non-optional to optional pointer" {
-    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
 
     const S = struct {
         fn doTheTest() !void {
@@ -384,12 +378,6 @@ test "pointer arithmetic affects the alignment" {
 }
 
 test "@ptrToInt on null optional at comptime" {
-    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
-    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
-
     {
         const pointer = @intToPtr(?*u8, 0x000);
         const x = @ptrToInt(pointer);