simd: simplify isa.funcMap, find Zig compiler bug

src/simd/isa.zig

@@ -142,7 +142,6 @@ inline fn hasMask(input: u32, mask: u32) bool {
 /// will not be included on x86_64.
 pub fn funcMap(
     comptime Func: type,
-    comptime name: []const u8,
     v: ISA,
     comptime map: anytype,
 ) *const Func {
@@ -153,7 +152,12 @@ pub fn funcMap(
 
             // Find the entry for this tag and return the function.
             inline for (map) |entry| {
-                if (entry[0] == tag) return @field(entry[1], name);
+                if (entry[0] == tag) {
+                    // If we return &entry[1] directly the compiler crashes:
+                    // https://github.com/ziglang/zig/issues/18754
+                    const func = entry[1];
+                    return &func;
+                }
             } else unreachable;
         },
     }

src/simd/utf8_count.zig

@@ -9,10 +9,10 @@ pub const Count = fn ([]const u8) usize;
 
 /// Returns the count function for the given ISA.
 pub fn countFunc(v: isa.ISA) *const Count {
-    return isa.funcMap(Count, "count", v, .{
-        .{ .avx2, Scalar }, // todo
-        .{ .neon, Neon },
-        .{ .scalar, Scalar },
+    return isa.funcMap(Count, v, .{
+        .{ .avx2, Scalar.count }, // todo
+        .{ .neon, Neon.count },
+        .{ .scalar, Scalar.count },
     });
 }
 

src/simd/utf8_validate.zig

@@ -12,10 +12,10 @@ const Validate = fn ([]const u8) bool;
 // - https://simdutf.github.io/simdutf/ (MIT License)
 
 pub fn validateFunc(v: isa.ISA) *const Validate {
-    return isa.funcMap(Validate, "validate", v, .{
-        .{ .avx2, Scalar }, // todo
-        .{ .neon, Neon },
-        .{ .scalar, Scalar },
+    return isa.funcMap(Validate, v, .{
+        .{ .avx2, Scalar.validate }, // todo
+        .{ .neon, Neon.validate },
+        .{ .scalar, Scalar.validate },
     });
 }