5 files changed, 17 insertions(+), 0 deletions(-)

M pkg/semantic/analysis_pass.go
M pkg/semantic/testdata/static/fn_generic_interface.snow.err
M pkg/semantic/testdata/static/fn_invalid_main.snow.err
M pkg/semantic/testdata/static/fn_nested_block.snow.err
M pkg/semantic/testdata/static/interface_satisfied.snow.err

@@ 42,6 42,16 @@ func (a *analysisVisitor) Visit(n Node) Visitor {
 
 	// ************** DECLARATIONS *****************
 
+	case *Fn:
+		// if the function has a body and does not return void, make sure
+		// every branch of the function has a return or does not fallthrough
+		// without returning.
+		if st := AsSignatureType(n.Type()); n.Body != nil && st != nil && !IsBasicOfKind(st.Return, Void) {
+			if FallsThrough(n.Body) {
+				a.errh(n.Pos(), "not all branches of the function body return a value")
+			}
+		}
+
 	case *Var:
 		if n.Value != nil {
 			aa := a.cloneRHS()

@@ 1,1 1,3 @@
+testdata/fn_generic_interface.snow:6:6: not all branches of the function body return a value
+testdata/fn_generic_interface.snow:10:6: not all branches of the function body return a value
 testdata/fn_generic_interface.snow:23:14: cannot assign type struct G[bool] to variable of type interface I[int]

@@ 1,1 1,2 @@
 testdata/fn_invalid_main.snow:1:4: main function must not have any parameter and return value, is (int) -> string
+testdata/fn_invalid_main.snow:1:4: not all branches of the function body return a value

@@ 1,1 1,2 @@
 main function missing
+testdata/fn_nested_block.snow:1:4: not all branches of the function body return a value

@@ 1,3 1,6 @@
+testdata/interface_satisfied.snow:9:6: not all branches of the function body return a value
+testdata/interface_satisfied.snow:19:6: not all branches of the function body return a value
+testdata/interface_satisfied.snow:23:10: not all branches of the function body return a value
 testdata/interface_satisfied.snow:39:11: cannot assign type int to variable of type interface Empty
 testdata/interface_satisfied.snow:42:7: cannot assign type struct S2 to variable of type interface Foo
 testdata/interface_satisfied.snow:43:7: cannot assign type struct S3 to variable of type interface Foo