AOT (Ahead Of Time) Compiler

Compiling Steps

Code analysis	Code generation	Template type checking
Creates a source sample but does not start compiling. Only records the syntax errors of the metadata	Keeps analyzing the syntax errors of the metadata and shows the errors	Checks the syntax of the binding in templates (Optional phase)

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To turn on the template type-checking option, add the following code in the angularCompilerOptions of the 'tsconfig.json'

"strictInjectionParameters": true

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    // ...
  },
  "angularCompilerOptions": {
    "enableI18nLegacyMessageIdFormat": false,
    "strictInjectionParameters": true, // Turns on the option
    // ...
  }
}

Source Code: https://angular.io/guide/angular-compiler-options

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How does it work

Code analysis

In this stage, the TypeScript compiler will analyze the code and creates '.d.ts' that stores the type information (the AOT compiler uses this to create an application code). AOT compiler creates '.d.ts' for each '.metadata.json' file using the data inside the decorators

Code generation

In this stage, the compiler checks any syntax error in the metadata. The collector accepts only those functions and static methods with one return value

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References

Angular