import blocks are only allowed in the root module

internal/configs/config_build.go

@@ -4,6 +4,7 @@
 package configs
 
 import (
+	"fmt"
 	"sort"
 
 	version "github.com/hashicorp/go-version"
@@ -101,6 +102,15 @@ func buildChildModules(parent *Config, walker ModuleWalker) (map[string]*Config,
 			})
 		}
 
+		if len(mod.Import) > 0 {
+			diags = diags.Append(&hcl.Diagnostic{
+				Severity: hcl.DiagError,
+				Summary:  "Invalid import configuration",
+				Detail:   fmt.Sprintf("An import block was detected in %q. Import blocks are only allowed in the root module.", child.Path),
+				Subject:  mod.Import[0].DeclRange.Ptr(),
+			})
+		}
+
 		ret[call.Name] = child
 	}
 

internal/configs/testdata/config-diagnostics/import-in-child-module/child/main.tf

@@ -0,0 +1,6 @@
+resource "aws_instance" "web" {}
+
+import {
+  to = aws_instance.web
+  id = "test"
+}

internal/configs/testdata/config-diagnostics/import-in-child-module/errors

@@ -0,0 +1 @@
+import-in-child-module/child/main.tf:3,1-7: Invalid import configuration; An import block was detected in "module.child". Import blocks are only allowed in the root module.

internal/configs/testdata/config-diagnostics/import-in-child-module/root.tf

@@ -0,0 +1,10 @@
+resource "aws_instance" "web" {}
+
+import {
+  to = aws_instance.web
+  id = "test"
+}
+
+module "child" {
+  source = "./child"
+}