diff --git a/src/semantic/index.ts b/src/semantic/index.ts
index 27923a53..bb5637a2 100644
--- a/src/semantic/index.ts
+++ b/src/semantic/index.ts
@@ -357,12 +357,16 @@ const checkFnDef = (fnDef: FnDef, ctx: Context): void => {
                 upcast(rs, rs.type!, returnTypeResolved, ctx)
             })
         } else {
-            if (!module.compiled && instScope?.rel.instanceDef.kind !== 'trait-def') {
+            if (!instScope) {
                 addWarning(ctx, noBodyFnError(ctx, fnDef))
+            } else {
+                if (instScope?.rel.instanceDef.kind !== 'trait-def') {
+                    addError(ctx, noBodyFnError(ctx, fnDef))
+                }
             }
-            if (instScope?.rel.instanceDef.kind === 'trait-def' && fnDef.pub) {
-                addWarning(ctx, unnecessaryPubMethodError(ctx, fnDef))
-            }
+        }
+        if (instScope?.rel.instanceDef.kind === 'trait-def' && fnDef.pub) {
+            addWarning(ctx, unnecessaryPubMethodError(ctx, fnDef))
         }
     }
 
diff --git a/src/semantic/semantic.spec.ts b/src/semantic/semantic.spec.ts
index 22c3389f..51a4f961 100644
--- a/src/semantic/semantic.spec.ts
+++ b/src/semantic/semantic.spec.ts
@@ -701,4 +701,28 @@ fn main() {
             expect(ctx.errors.map(e => e.message)).toEqual(['missing variable initialization'])
         })
     })
+
+    describe('fn def', () => {
+        it('fn no body', () => {
+            const code = `\
+type Node<T> {
+    Node(node: Node<T>),
+    Leaf(t: T)
+}
+
+impl <T> Node<T> {
+    fn child()
+}
+
+fn main() {
+    let n = Node(Node(Leaf(5)))
+    n.child().child()
+}`
+            const ctx = check(code)
+            expect(ctx.errors.map(e => e.message)).toEqual([
+                'fn `child` has no body',
+                'method `std::unit::Unit::child` not found'
+            ])
+        })
+    })
 })
diff --git a/src/typecheck/generic.ts b/src/typecheck/generic.ts
index a742f7c0..9d316955 100644
--- a/src/typecheck/generic.ts
+++ b/src/typecheck/generic.ts
@@ -6,7 +6,7 @@ import { VirtualFnType, VirtualType } from './index'
 import { holeType, selfType } from './type'
 
 export const makeFnGenericMap = (fnType: VirtualFnType, argTypes: VirtualType[]): Map<string, VirtualType> => {
-    assert(argTypes.length <= fnType.paramTypes.length, 'fn args > params')
+    if (argTypes.length > fnType.paramTypes.length) return new Map()
     return argTypes
         .map((argType, i) => {
             const param = fnType.paramTypes[i]