From ea356eccd49d01c76d96c70b470c9be7e943ebf6 Mon Sep 17 00:00:00 2001
From: odow <o.dowson@gmail.com>
Date: Sat, 13 Jul 2024 16:26:00 +1200
Subject: [PATCH] Improve error message for common incorrect syntax in
 constraint macro

---
 src/macros/@constraint.jl | 19 +++++++++++++++++++
 test/test_macros.jl       | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/src/macros/@constraint.jl b/src/macros/@constraint.jl
index 87d1e47726b..9789971cbe6 100644
--- a/src/macros/@constraint.jl
+++ b/src/macros/@constraint.jl
@@ -417,6 +417,25 @@ function parse_constraint_head(error_fn::Function, ::Val{T}, args...) where {T}
     )
 end
 
+function parse_constraint_head(
+    error_fn::Function,
+    ::Union{Val{:vect},Val{:vcat}},
+    args...,
+)
+    return error_fn(
+        """
+        Unsupported constraint expression: we don't know how to parse a
+        `[ ]` block as a constraint. Have you written:
+        ```julia
+        @constraint(model, name, [...], ...)
+        ```
+        instead of:
+        ```julia
+        @constraint(model, name[...], ...)
+        ```""",
+    )
+end
+
 function parse_constraint_head(
     error_fn::Function,
     ::Val{:call},
diff --git a/test/test_macros.jl b/test/test_macros.jl
index 6b559667f22..bb80c711579 100644
--- a/test/test_macros.jl
+++ b/test/test_macros.jl
@@ -2407,4 +2407,40 @@ function test_unsupported_name_syntax_multiple_ref()
     return
 end
 
+function test_constraint_vect_vcat()
+    model = Model()
+    @variable(model, x)
+    @test_throws_parsetime(
+        ErrorException(
+            """
+            In `@constraint(model, c, [k in 1:2], x <= k)`: Unsupported constraint expression: we don't know how to parse a
+            `[ ]` block as a constraint. Have you written:
+            ```julia
+            @constraint(model, name, [...], ...)
+            ```
+            instead of:
+            ```julia
+            @constraint(model, name[...], ...)
+            ```""",
+        ),
+        @constraint(model, c, [k in 1:2], x <= k),
+    )
+    @test_throws_parsetime(
+        ErrorException(
+            """
+            In `@constraint(model, c, [k in 1:2; isodd(k)], x <= k)`: Unsupported constraint expression: we don't know how to parse a
+            `[ ]` block as a constraint. Have you written:
+            ```julia
+            @constraint(model, name, [...], ...)
+            ```
+            instead of:
+            ```julia
+            @constraint(model, name[...], ...)
+            ```""",
+        ),
+        @constraint(model, c, [k in 1:2; isodd(k)], x <= k),
+    )
+    return
+end
+
 end  # module