From 505e720421ce4f7ed11730fe68d32e3bba711f3c Mon Sep 17 00:00:00 2001
From: John Schmidt <john.schmidt.h@gmail.com>
Date: Wed, 8 Mar 2023 17:49:52 +0100
Subject: [PATCH] sema: add peer type resolution for vectors

This is consistent with how coercion for vectors work. So now you can do
this:

```
var a: @Vector(2, u16) = .{1, 2};
var b: @Vector(2, u8) = .{2, 1};
const c = @min(a, b);
```

where previously you had to cast explicitly:

```
var a: @Vector(2, u16) = .{1, 2};
var b: @Vector(2, u8) = .{2, 1};
var c: @Vector(2, u16) = b;
const c = @min(a, c);
```
---
 src/Sema.zig             | 25 +++++++++++++++++++++++++
 test/behavior/vector.zig | 19 +++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/src/Sema.zig b/src/Sema.zig
index 8c6e3cf05c..a33c9bee6d 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -29875,6 +29875,31 @@ fn resolvePeerTypes(
                 continue;
             },
             .Vector => switch (chosen_ty_tag) {
+                .Vector => {
+                    const chosen_len = chosen_ty.vectorLen();
+                    const candidate_len = candidate_ty.vectorLen();
+                    if (chosen_len != candidate_len)
+                        continue;
+
+                    const chosen_child_ty = chosen_ty.childType();
+                    const candidate_child_ty = candidate_ty.childType();
+                    if (chosen_child_ty.zigTypeTag() == .Int and candidate_child_ty.zigTypeTag() == .Int) {
+                        const chosen_info = chosen_child_ty.intInfo(target);
+                        const candidate_info = candidate_child_ty.intInfo(target);
+                        if (chosen_info.bits < candidate_info.bits) {
+                            chosen = candidate;
+                            chosen_i = candidate_i + 1;
+                        }
+                        continue;
+                    }
+                    if (chosen_child_ty.zigTypeTag() == .Float and candidate_child_ty.zigTypeTag() == .Float) {
+                        if (chosen_ty.floatBits(target) < candidate_ty.floatBits(target)) {
+                            chosen = candidate;
+                            chosen_i = candidate_i + 1;
+                        }
+                        continue;
+                    }
+                },
                 .Array => {
                     chosen = candidate;
                     chosen_i = candidate_i + 1;
diff --git a/test/behavior/vector.zig b/test/behavior/vector.zig
index 1d9d517a96..2c7be227c4 100644
--- a/test/behavior/vector.zig
+++ b/test/behavior/vector.zig
@@ -175,6 +175,25 @@ test "array to vector" {
     comptime try S.doTheTest();
 }
 
+test "peer type resolution with coercible element types" {
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
+
+    const S = struct {
+        fn doTheTest() !void {
+            var b: @Vector(2, u8) = .{ 1, 2 };
+            var a: @Vector(2, u16) = .{ 2, 1 };
+            var t: bool = true;
+            var c = if (t) a else b;
+            try std.testing.expect(@TypeOf(c) == @Vector(2, u16));
+        }
+    };
+    comptime try S.doTheTest();
+}
+
 test "tuple to vector" {
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO