Sema: implement peer type resolution of function pointers and function bodies

Closes  #13438

2 files changed, 22 insertions, 0 deletions

diff --git a/src/Sema.zig b/src/Sema.zig
index 3def393dfb..a127031808 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -28769,6 +28769,13 @@ fn resolvePeerTypes(
                             }
                         }
                     },
+                    .Fn => {
+                        if (!cand_info.mutable and cand_info.pointee_type.zigTypeTag() == .Fn and .ok == try sema.coerceInMemoryAllowedFns(block, chosen_ty, cand_info.pointee_type, target, src, src)) {
+                            chosen = candidate;
+                            chosen_i = candidate_i + 1;
+                            continue;
+                        }
+                    },
                     else => {},
                 }
             },
@@ -28799,6 +28806,11 @@ fn resolvePeerTypes(
                 .Vector => continue,
                 else => {},
             },
+            .Fn => if (chosen_ty.isSinglePointer() and chosen_ty.isConstPtr() and chosen_ty.childType().zigTypeTag() == .Fn) {
+                if (.ok == try sema.coerceInMemoryAllowedFns(block, chosen_ty.childType(), candidate_ty, target, src, src)) {
+                    continue;
+                }
+            },
             else => {},
         }
 
diff --git a/test/behavior/cast.zig b/test/behavior/cast.zig
index 07d45ad3dc..0de4b6d53e 100644
--- a/test/behavior/cast.zig
+++ b/test/behavior/cast.zig
@@ -1419,3 +1419,13 @@ test "floatToInt to zero-bit int" {
     var a: f32 = 0.0;
     comptime try std.testing.expect(@floatToInt(u0, a) == 0);
 }
+
+test "peer type resolution of function pointer and function body" {
+    if (builtin.zig_backend == .stage1) return error.SkipZigTest;
+
+    const T = fn () u32;
+    const a: T = undefined;
+    const b: *const T = undefined;
+    try expect(@TypeOf(a, b) == *const fn () u32);
+    try expect(@TypeOf(b, a) == *const fn () u32);
+}