Allow C pointers as valid self parameters in method detection

This change updates firstParamIs to accept
`[*c]T` pointers as equivalent to `*T` pointers
when checking if a function's first parameter
matches the container type, enabling proper method
completion for functions with C pointer receivers.

Author: fomgleb

src/analysis.zig

@@ -461,16 +461,16 @@ pub fn firstParamIs(
 
     const deref_type = switch (resolved_type.data) {
         .pointer => |info| switch (info.size) {
-            .one => info.elem_ty.*,
-            .many, .slice, .c => return false,
+            .one, .c => info.elem_ty.*,
+            .many, .slice => return false,
         },
         else => resolved_type,
     };
 
     const deref_expected_type = switch (expected_type.data) {
         .pointer => |info| switch (info.size) {
-            .one => info.elem_ty.*,
-            .many, .slice, .c => return false,
+            .one, .c => info.elem_ty.*,
+            .many, .slice => return false,
         },
         else => expected_type,
     };

tests/lsp_features/completion.zig

@@ -1337,18 +1337,21 @@ test "struct" {
         \\fn fooImpl(_: Foo) void {}
         \\fn barImpl(_: *const Foo) void {}
         \\fn bazImpl(_: u32) void {}
+        \\fn quxImpl(_: [*c]const Foo) void {}
         \\const Foo = struct {
         \\    alpha: u32,
         \\    pub const foo = fooImpl;
         \\    pub const bar = barImpl;
         \\    pub const baz = bazImpl;
+        \\    pub const qux = quxImpl;
         \\};
         \\const foo = Foo{};
         \\const baz = foo.<cursor>;
     , &.{
         .{ .label = "alpha", .kind = .Field, .detail = "u32" },
         .{ .label = "foo", .kind = .Method, .detail = "fn (_: Foo) void" },
         .{ .label = "bar", .kind = .Method, .detail = "fn (_: *const Foo) void" },
+        .{ .label = "qux", .kind = .Method, .detail = "fn (_: [*c]const Foo) void" },
     });
     try testCompletion(
         \\alpha: u32,