Function infer_types 

pub fn infer_types(
    interner: &mut Interner,
    ast_map: &IndexMap<SourceId, Root>,
    symbol_table: &SymbolTable,
    dependency_analysis: &DependencyAnalysis,
    diag: &mut Diagnostics,
) -> TypeContext

Run type inference on all definitions.

Processes definitions in dependency order (leaves first) to handle recursive definitions correctly.