TypeScriptToLua · Perryvw · Mar 19, 2023 · Mar 18, 2023
diff --git a/src/transformation/visitors/binary-expression/compound.ts b/src/transformation/visitors/binary-expression/compound.ts
@@ -1,12 +1,13 @@
 import * as ts from "typescript";
 import * as lua from "../../../LuaAST";
-import { cast, assertNever } from "../../../utils";
+import { assertNever } from "../../../utils";
 import { TransformationContext } from "../../context";
 import { transformInPrecedingStatementScope, WithPrecedingStatements } from "../../utils/preceding-statements";
 import { transformBinaryOperation } from "./index";
 import { transformAssignmentWithRightPrecedingStatements } from "./assignments";
 import { isArrayLength } from "./destructuring-assignments";
 import { LuaLibFeature, transformLuaLibFunction } from "../../utils/lualib";
+import { cannotAssignToNodeOfKind } from "../../utils/diagnostics";
 
 function isLuaExpressionWithSideEffect(expression: lua.Expression) {
     return !(lua.isLiteral(expression) || lua.isIdentifier(expression));
@@ -85,7 +86,12 @@ function transformCompoundAssignment(
         return { precedingStatements, result: lengthSetterStatement.expression };
     }
 
-    const left = cast(context.transformExpression(lhs), lua.isAssignmentLeftHandSideExpression);
+    const left = context.transformExpression(lhs);
+    if (!lua.isAssignmentLeftHandSideExpression(left)) {
+        context.diagnostics.push(cannotAssignToNodeOfKind(expression, left.kind));
+        return { precedingStatements: [], result: left };
+    }
+
     const { precedingStatements: rightPrecedingStatements, result: right } = transformInPrecedingStatementScope(
         context,
         () => context.transformExpression(rhs)
@@ -250,7 +256,12 @@ export function transformCompoundAssignmentStatement(
         return [...precedingStatements, lengthSetterStatement];
     }
 
-    const left = cast(context.transformExpression(lhs), lua.isAssignmentLeftHandSideExpression);
+    const left = context.transformExpression(lhs);
+    if (!lua.isAssignmentLeftHandSideExpression(left)) {
+        context.diagnostics.push(cannotAssignToNodeOfKind(node, left.kind));
+        return [];
+    }
+
     const { precedingStatements: rightPrecedingStatements, result: right } = transformInPrecedingStatementScope(
         context,
         () => context.transformExpression(rhs)

diff --git a/test/unit/assignments.spec.ts b/test/unit/assignments.spec.ts
@@ -506,3 +506,13 @@ test.each([
         return [obj, objGot];
     `.expectToMatchJsResult();
 });
+
+// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1412
+test("invalid assignment to call expression (#1412)", () => {
+    util.testFunction`
+        function foo(): number {
+            return 3;
+        }
+        foo() += 4;
+    `.expectNoTranspileException();
+});
diff --git a/test/util.ts b/test/util.ts
@@ -313,12 +313,23 @@ export abstract class TestBuilder {
     // Actions
 
     public debug(includeLualib = false): this {
-        const transpiledFiles = this.getLuaResult().transpiledFiles;
+        const { transpiledFiles, diagnostics } = this.getLuaResult();
         const luaCode = transpiledFiles
             .filter(f => includeLualib || f.outPath !== "lualib_bundle.lua")
             .map(f => `[${f.outPath}]:\n${f.lua?.replace(/^/gm, "  ")}`);
         const value = prettyFormat.format(this.getLuaExecutionResult()).replace(/^/gm, "  ");
         console.log(`Lua Code:\n${luaCode.join("\n")}\n\nValue:\n${value}`);
+
+        if (diagnostics.length > 0) {
+            console.log(
+                ts.formatDiagnostics(diagnostics.map(tstl.prepareDiagnosticForFormatting), {
+                    getCurrentDirectory: () => "",
+                    getCanonicalFileName: fileName => fileName,
+                    getNewLine: () => "\n",
+                })
+            );
+        }
+
         return this;
     }