diff --git a/addrs/provider.go b/addrs/provider.go
index 0514ed6c6..01284300f 100644
--- a/addrs/provider.go
+++ b/addrs/provider.go
@@ -126,6 +126,25 @@ func (pt Provider) LessThan(other Provider) bool {
 	}
 }
 
+// IsLegacy returns true if the provider is a legacy-style provider
+func (pt Provider) IsLegacy() bool {
+	if pt.IsZero() {
+		panic("called IsLegacy() on zero-value addrs.Provider")
+	}
+
+	return pt.Hostname == DefaultRegistryHost && pt.Namespace == LegacyProviderNamespace
+
+}
+
+// IsDefault returns true if the provider is a default hashicorp provider
+func (pt Provider) IsDefault() bool {
+	if pt.IsZero() {
+		panic("called IsDefault() on zero-value addrs.Provider")
+	}
+
+	return pt.Hostname == DefaultRegistryHost && pt.Namespace == "hashicorp"
+}
+
 // Equals returns true if the receiver and other provider have the same attributes.
 func (pt Provider) Equals(other Provider) bool {
 	return pt == other
diff --git a/addrs/provider_test.go b/addrs/provider_test.go
index cf97bb0c3..fe5344a18 100644
--- a/addrs/provider_test.go
+++ b/addrs/provider_test.go
@@ -7,6 +7,84 @@ import (
 	svchost "github.com/hashicorp/terraform-svchost"
 )
 
+func TestProviderIsDefault(t *testing.T) {
+	tests := []struct {
+		Input Provider
+		Want  bool
+	}{
+		{
+			Provider{
+				Type:      "test",
+				Hostname:  DefaultRegistryHost,
+				Namespace: "hashicorp",
+			},
+			true,
+		},
+		{
+			Provider{
+				Type:      "test",
+				Hostname:  "registry.terraform.com",
+				Namespace: "hashicorp",
+			},
+			false,
+		},
+		{
+			Provider{
+				Type:      "test",
+				Hostname:  DefaultRegistryHost,
+				Namespace: "othercorp",
+			},
+			false,
+		},
+	}
+
+	for _, test := range tests {
+		got := test.Input.IsDefault()
+		if got != test.Want {
+			t.Errorf("wrong result for %s\n", test.Input.String())
+		}
+	}
+}
+
+func TestProviderIsLegacy(t *testing.T) {
+	tests := []struct {
+		Input Provider
+		Want  bool
+	}{
+		{
+			Provider{
+				Type:      "test",
+				Hostname:  DefaultRegistryHost,
+				Namespace: LegacyProviderNamespace,
+			},
+			true,
+		},
+		{
+			Provider{
+				Type:      "test",
+				Hostname:  "registry.terraform.com",
+				Namespace: LegacyProviderNamespace,
+			},
+			false,
+		},
+		{
+			Provider{
+				Type:      "test",
+				Hostname:  DefaultRegistryHost,
+				Namespace: "hashicorp",
+			},
+			false,
+		},
+	}
+
+	for _, test := range tests {
+		got := test.Input.IsLegacy()
+		if got != test.Want {
+			t.Errorf("wrong result for %s\n", test.Input.String())
+		}
+	}
+}
+
 func TestParseProviderSourceStr(t *testing.T) {
 	tests := map[string]struct {
 		Want Provider
diff --git a/configs/config_test.go b/configs/config_test.go
index ec85208cd..61149920f 100644
--- a/configs/config_test.go
+++ b/configs/config_test.go
@@ -9,12 +9,18 @@ import (
 )
 
 func TestConfigProviderTypes(t *testing.T) {
+	// nil cfg should return an empty map
+	got := NewEmptyConfig().ProviderTypes()
+	if len(got) != 0 {
+		t.Fatal("expected empty result from empty config")
+	}
+
 	cfg, diags := testModuleConfigFromFile("testdata/valid-files/providers-explicit-implied.tf")
 	if diags.HasErrors() {
 		t.Fatal(diags.Error())
 	}
 
-	got := cfg.ProviderTypes()
+	got = cfg.ProviderTypes()
 	want := []addrs.Provider{
 		addrs.NewLegacyProvider("aws"),
 		addrs.NewLegacyProvider("null"),
diff --git a/configs/module_merge_test.go b/configs/module_merge_test.go
index d4cb3f5a7..991bb9fad 100644
--- a/configs/module_merge_test.go
+++ b/configs/module_merge_test.go
@@ -297,6 +297,27 @@ func TestMergeProviderVersionConstraints(t *testing.T) {
 				},
 			},
 		},
+		"merge with source constraint": {
+			map[string]ProviderRequirements{
+				"random": ProviderRequirements{
+					Type:               addrs.Provider{Type: "random"},
+					VersionConstraints: []VersionConstraint{vc1},
+				},
+			},
+			[]*RequiredProvider{
+				&RequiredProvider{
+					Name:        "random",
+					Source:      Source{SourceStr: "hashicorp/random"},
+					Requirement: vc2,
+				},
+			},
+			map[string]ProviderRequirements{
+				"random": ProviderRequirements{
+					Type:               addrs.NewDefaultProvider("random"),
+					VersionConstraints: []VersionConstraint{vc2},
+				},
+			},
+		},
 	}
 
 	for name, test := range tests {
diff --git a/configs/module_test.go b/configs/module_test.go
index aab08a4a2..81d05ea35 100644
--- a/configs/module_test.go
+++ b/configs/module_test.go
@@ -27,6 +27,12 @@ func TestNewModule_provider_local_name(t *testing.T) {
 	if localName != "foo-test" {
 		t.Fatal("provider local name not found")
 	}
+
+	// if there is not a local name for a provider, it should return the type name
+	localName = mod.LocalNameForProvider(addrs.NewLegacyProvider("nonexist"))
+	if localName != "nonexist" {
+		t.Error("wrong local name returned for a non-local provider")
+	}
 }
 
 // This test validates the provider FQNs set in each Resource