Semantic: resolve arguments' generics before type checking

src/semantic/instance.ts

@@ -147,6 +147,9 @@ export const checkMethodCall = (expr: UnaryExpr, mCall: MethodCallOp, ctx: Conte
 
     let genericMaps = makeMethodGenericMaps(operand, ref.def, mCall, ctx)
     const args = ref.def.fn.static ? mCall.call.args.map(a => a.expr) : [operand, ...mCall.call.args.map(a => a.expr)]
+    args.forEach(a => {
+        a.type = resolveType(a.type!, genericMaps, ctx)
+    })
     const paramTypes = fnType.paramTypes.map(pt => resolveType(pt, genericMaps, ctx))
     checkCallArgs(mCall, args, paramTypes, ctx)
     // recalculate generic maps since malleable args might've been updated
@@ -203,7 +206,8 @@ export const makeMethodGenericMaps = (
     implForGenericMap.delete(selfType.name)
     maps.push(implForGenericMap)
 
-    const fnGenericMap = makeFnGenericMap(fnType, [lOperand.type!, ...call.call.args.map(a => a.expr.type!)])
+    const args = [lOperand.type!, ...call.call.args.map(a => a.expr.type!)]
+    const fnGenericMap = makeFnGenericMap(fnType, args)
     maps.push(fnGenericMap)
 
     return maps

src/typecheck/generic.ts

@@ -1,7 +1,7 @@
 import { Context, InstanceScope } from '../scope'
 import { getInstanceForType } from '../scope/trait'
 import { merge } from '../util/map'
-import { assert, unreachable } from '../util/todo'
+import { assert } from '../util/todo'
 import { VirtualFnType, VirtualType } from './index'
 import { holeType, selfType } from './type'
 
@@ -54,7 +54,7 @@ export const makeGenericMapOverStructure = (arg: VirtualType, param: VirtualType
             const paramType = param.paramTypes[i]
             const argType = arg.paramTypes.at(i)
             if (!argType) break
-            makeGenericMapOverStructure(argType, paramType).forEach((v, k) => map.set(k, v))
+            makeGenericMapOverStructure(paramType, argType).forEach((v, k) => map.set(k, v))
         }
         makeGenericMapOverStructure(arg.returnType, param.returnType).forEach((v, k) => map.set(k, v))
     } else {
@@ -222,7 +222,7 @@ const resolveGenericMap = (
             }
         case 'hole-type':
         case 'unknown-type':
+        case 'malleable-type':
             return undefined
     }
-    return unreachable()
 }