check for duplicate defaults from resource names

internal/configs/config_test.go

@@ -160,7 +160,7 @@ func TestConfigProviderRequirements(t *testing.T) {
 
 func TestConfigProviderRequirementsDuplicate(t *testing.T) {
 	_, diags := testNestedModuleConfigFromDir(t, "testdata/duplicate-local-name")
-	assertDiagnosticCount(t, diags, 2)
+	assertDiagnosticCount(t, diags, 3)
 	assertDiagnosticSummary(t, diags, "Duplicate required provider")
 }
 

internal/configs/provider_validation.go

@@ -118,7 +118,7 @@ func validateProviderConfigs(parentCall *ModuleCall, cfg *Config, noProviderConf
 							Severity: hcl.DiagWarning,
 							Summary:  "Duplicate required provider",
 							Detail: fmt.Sprintf(
-								"Provider %s with the local name %q was implicitly required via a configuration block as %q. Make sure the provider configuration block name matches the name used in required_providers.",
+								"Provider %s with the local name %q was implicitly required via a configuration block as %q. The provider configuration block name must match the name used in required_providers.",
 								req.Type.ForDisplay(), req.Name, req.Type.Type,
 							),
 							Subject: &req.DeclRange,
@@ -142,6 +142,44 @@ func validateProviderConfigs(parentCall *ModuleCall, cfg *Config, noProviderConf
 		}
 	}
 
+	checkImpliedProviderNames := func(resourceConfigs map[string]*Resource) {
+		// Now that we have all the provider configs and requirements validated,
+		// check for any resources which use an implied localname which doesn't
+		// match that of required_providers
+		for _, r := range resourceConfigs {
+			// We're looking for resources with no specific provider reference
+			if r.ProviderConfigRef != nil {
+				continue
+			}
+
+			localName := r.Addr().ImpliedProvider()
+			if _, ok := localNames[localName]; ok {
+				// OK, this was listed directly in the required_providers
+				continue
+			}
+
+			defAddr := addrs.ImpliedProviderForUnqualifiedType(localName)
+
+			// Now make sure we don't have the same provider required under a
+			// different name.
+			for prevLocalName, addr := range localNames {
+				if addr.Equals(defAddr) {
+					diags = append(diags, &hcl.Diagnostic{
+						Severity: hcl.DiagWarning,
+						Summary:  "Duplicate required provider",
+						Detail: fmt.Sprintf(
+							"Provider %q was implicitly required via resource %q, but listed in required_providers as %q. Either the local name in required_providers must match the resource name, or the %q provider must be assigned within the resource block.",
+							defAddr, r.Addr(), prevLocalName, prevLocalName,
+						),
+						Subject: &r.DeclRange,
+					})
+				}
+			}
+		}
+	}
+	checkImpliedProviderNames(mod.ManagedResources)
+	checkImpliedProviderNames(mod.DataResources)
+
 	// collect providers passed from the parent
 	if parentCall != nil {
 		for _, passed := range parentCall.Providers {

internal/configs/testdata/duplicate-local-name/main.tf

@@ -9,8 +9,15 @@ terraform {
     other = {
       source = "hashicorp/default"
     }
+
+    wrong-name = {
+      source = "hashicorp/foo"
+    }
   }
 }
 
 provider "default" {
 }
+
+resource "foo_resource" {
+}