Add error for global methods inside function scope

Author: c42f

src/scope_analysis.jl

@@ -539,6 +539,19 @@ function _resolve_scopes(ctx, ex::SyntaxTree)
             throw(LoweringError(ex, "Unknown syntax assertion"))
         end
         makeleaf(ctx, ex, K"TOMBSTONE")
+    elseif k == K"function_decl"
+        resolved = mapchildren(e->_resolve_scopes(ctx, e), ctx, ex)
+        name = resolved[1]
+        if kind(name) == K"BindingId"
+            bk = lookup_binding(ctx, name).kind
+            if bk == :argument
+                throw(LoweringError(name, "Cannot add method to a function argument"))
+            elseif bk == :global && !ctx.scope_stack[end].in_toplevel_thunk
+                throw(LoweringError(name, 
+                    "Global method definition needs to be placed at the top level, or use `eval()`"))
+            end
+        end
+        resolved
     elseif k == K"const_if_global"
         id = _resolve_scopes(ctx, ex[1])
         if lookup_binding(ctx, id).kind == :global
@@ -630,9 +643,6 @@ function analyze_variables!(ctx, ex)
         analyze_variables!(ctx, ex[2])
     elseif k == K"function_decl"
         name = ex[1]
-        if kind(name) == K"BindingId" && lookup_binding(ctx, name).kind == :argument
-            throw(LoweringError(name, "Cannot add method to a function argument"))
-        end
         if lookup_binding(ctx, name.var_id).kind === :local
             init_closure_bindings!(ctx, name)
         end

test/closures_ir.jl

@@ -422,20 +422,6 @@ end
 18  (call core.kwcall %₅ %₁ %₁₆ %₁₇)
 19  (return %₁₈)
 
-########################################
-# Error: Attempt to add methods to a function argument
-function f(g)
-    function g()
-    end
-end
-#---------------------
-LoweringError:
-function f(g)
-    function g()
-#            ╙ ── Cannot add method to a function argument
-    end
-end
-
 ########################################
 # Error: Static parameter clashing with closure name
 function f(::g) where {g}

test/scopes_ir.jl

@@ -379,6 +379,36 @@ function f(::T) where T
     end
 end
 
+########################################
+# Error: Attempt to add methods to a function argument
+function f(g)
+    function g()
+    end
+end
+#---------------------
+LoweringError:
+function f(g)
+    function g()
+#            ╙ ── Cannot add method to a function argument
+    end
+end
+
+########################################
+# Error: Global method definition inside function scope
+function f()
+    global global_method
+    function global_method()
+    end
+end
+#---------------------
+LoweringError:
+function f()
+    global global_method
+    function global_method()
+#            └───────────┘ ── Global method definition needs to be placed at the top level, or use `eval()`
+    end
+end
+
 ########################################
 # @isdefined with defined variables
 let x = 1