add back multi-function call check

Signed-off-by: Achille Roussel <[email protected]>

compiler/coroutine_test.go

@@ -105,11 +105,13 @@ func TestCoroutineYield(t *testing.T) {
 			yields: []int{0, 2, 4, 6, 8, 10, 12, 14, 16, 18},
 		},
 
-		{
-			name:   "range over anonymous function",
-			coro:   func() { RangeTriple(4) },
-			yields: []int{0, 3, 6, 9},
-		},
+		// TODO: desugar function call expressions to enable this test.
+		//
+		// {
+		// 	name:   "range over anonymous function",
+		// 	coro:   func() { RangeTriple(4) },
+		// 	yields: []int{0, 3, 6, 9},
+		// },
 
 		{
 			name:   "range over anonymous function value",

compiler/testdata/coroutine.go

@@ -266,11 +266,11 @@ func Double(n int) {
 	coroutine.Yield[int, any](2 * n)
 }
 
-func RangeTriple(n int) {
-	Range(n, func(i int) {
-		coroutine.Yield[int, any](3 * i)
-	})
-}
+// func RangeTriple(n int) {
+// 	Range(n, func(i int) {
+// 		coroutine.Yield[int, any](3 * i)
+// 	})
+// }
 
 func RangeTripleFuncValue(n int) {
 	f := func(i int) {

compiler/unsupported.go

@@ -11,6 +11,14 @@ import (
 func unsupported(decl ast.Node, info *types.Info) (err error) {
 	ast.Inspect(decl, func(node ast.Node) bool {
 		switch nn := node.(type) {
+		case ast.Expr:
+			switch nn.(type) {
+			case *ast.FuncLit:
+			default:
+				if countFunctionCalls(nn, info) > 1 {
+					err = fmt.Errorf("not implemented: multiple function calls in an expression")
+				}
+			}
 		case ast.Stmt:
 			switch n := nn.(type) {
 			// Not yet supported:
@@ -74,3 +82,35 @@ func unsupported(decl ast.Node, info *types.Info) (err error) {
 	})
 	return
 }
+
+func countFunctionCalls(expr ast.Expr, info *types.Info) (count int) {
+	ast.Inspect(expr, func(node ast.Node) bool {
+		c, ok := node.(*ast.CallExpr)
+		if !ok {
+			return true
+		}
+		switch f := c.Fun.(type) {
+		case *ast.Ident:
+			if obj := info.ObjectOf(f); types.Universe.Lookup(f.Name) == obj {
+				return true // skip builtins
+			} else if _, ok := obj.(*types.TypeName); ok {
+				return true // skip type casts
+			}
+		case *ast.SelectorExpr:
+			if x, ok := f.X.(*ast.Ident); ok {
+				if obj := info.ObjectOf(x); obj != nil {
+					if pkg, ok := obj.(*types.PkgName); ok {
+						pkgPath := pkg.Imported().Path()
+						switch {
+						case pkgPath == "unsafe":
+							return true // skip unsafe intrinsics
+						}
+					}
+				}
+			}
+		}
+		count++
+		return true
+	})
+	return
+}