From 86e6acb37b242a60917f5552999d918c24fdf791 Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Fri, 2 Dec 2022 15:39:40 +0200
Subject: [PATCH] AstGen: improve error message for missing parameter name

Closes #13393
---
 src/AstGen.zig                                | 23 +++++++++++++++++++
 .../compile_errors/missing_parameter_name.zig | 19 +++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 test/cases/compile_errors/missing_parameter_name.zig

diff --git a/src/AstGen.zig b/src/AstGen.zig
index 009d05e5ed..b18d550347 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -3696,6 +3696,29 @@ fn fnDecl(
                 if (param.anytype_ellipsis3) |tok| {
                     return astgen.failTok(tok, "missing parameter name", .{});
                 } else {
+                    ambiguous: {
+                        if (tree.nodes.items(.tag)[param.type_expr] != .identifier) break :ambiguous;
+                        const main_token = tree.nodes.items(.main_token)[param.type_expr];
+                        const identifier_str = tree.tokenSlice(main_token);
+                        if (isPrimitive(identifier_str)) break :ambiguous;
+                        return astgen.failNodeNotes(
+                            param.type_expr,
+                            "missing parameter name or type",
+                            .{},
+                            &[_]u32{
+                                try astgen.errNoteNode(
+                                    param.type_expr,
+                                    "if this is a name, annotate its type '{s}: T'",
+                                    .{identifier_str},
+                                ),
+                                try astgen.errNoteNode(
+                                    param.type_expr,
+                                    "if this is a type, give it a name '<name>: {s}'",
+                                    .{identifier_str},
+                                ),
+                            },
+                        );
+                    }
                     return astgen.failNode(param.type_expr, "missing parameter name", .{});
                 }
             } else 0;
diff --git a/test/cases/compile_errors/missing_parameter_name.zig b/test/cases/compile_errors/missing_parameter_name.zig
new file mode 100644
index 0000000000..3e576a1a6d
--- /dev/null
+++ b/test/cases/compile_errors/missing_parameter_name.zig
@@ -0,0 +1,19 @@
+fn f2(u64) u64 {
+    return x;
+}
+fn f3(*x) u64 {
+    return x;
+}
+fn f1(x) u64 {
+    return x;
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :1:7: error: missing parameter name
+// :4:7: error: missing parameter name
+// :7:7: error: missing parameter name or type
+// :7:7: note: if this is a name, annotate its type 'x: T'
+// :7:7: note: if this is a type, give it a name '<name>: x'