refactor(generators): Migrate Dart generators to TypeScript (#7646)

* refactor(generators): Migrate dart_generator.js to TypeScript

* refactor(generators): Simplify getAdjusted

  Slightly simplify the implementation of getAdjusted, in part to
  make it more readable.  Also improve its JSDoc comment.

* refactor(generators): Migrate generators/dart/* to TypeScript

  First pass doing very mechanistic migration, not attempting to fix
  all the resulting type errors.

* fix(generators): Fix type errors in generator functions

  This consists almost entirely of adding casts, so the code output
  by tsc should be as similar as possible to the pre-migration .js
  source files.

* fix(generators): Fix minor inconsistencies in JS and Python

  The migration of the JavaScript and Python generators
  inadvertently introduced some inconsistencies in the code,
  e.g.:

  - Incorrect import ordering.
  - Putting executable code before the initial comment line that
    most generator functions begin with, and/or deleting or
    replacing these comments.
    -  N.B. however that these inline comments should have been
       JSDocs; a task to convert them has been added to #7600.

* refactor(generators): Migrate generators/dart.js to TypeScript

  The way the generator functions are added to
  dartGenerator.forBlock has been modified so that incorrect
  generator function signatures will cause tsc to generate a type
  error.

* chore(generator): Format

  One block protected with // prettier-ignore to preserve careful
  comment formatting.

  Where there are repeated concatenations prettier has made a pretty
  mess of things, but the correct fix is probably to use template
  literals instead (rather than just locally disabling prettier).
  This is one of the items in the to-do list in #7600.

* fix(generators): Fix for PR #7646

generators/dart/procedures.ts

@@ -0,0 +1,129 @@
+/**
+ * @license
+ * Copyright 2014 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Generating Dart for procedure blocks.
+ */
+
+// Former goog.module ID: Blockly.Dart.procedures
+
+import type {Block} from '../../core/block.js';
+import type {IfReturnBlock} from '../../blocks/procedures.js';
+import type {DartGenerator} from './dart_generator.js';
+import {Order} from './dart_generator.js';
+
+export function procedures_defreturn(block: Block, generator: DartGenerator) {
+  // Define a procedure with a return value.
+  const funcName = generator.getProcedureName(block.getFieldValue('NAME'));
+  let xfix1 = '';
+  if (generator.STATEMENT_PREFIX) {
+    xfix1 += generator.injectId(generator.STATEMENT_PREFIX, block);
+  }
+  if (generator.STATEMENT_SUFFIX) {
+    xfix1 += generator.injectId(generator.STATEMENT_SUFFIX, block);
+  }
+  if (xfix1) {
+    xfix1 = generator.prefixLines(xfix1, generator.INDENT);
+  }
+  let loopTrap = '';
+  if (generator.INFINITE_LOOP_TRAP) {
+    loopTrap = generator.prefixLines(
+      generator.injectId(generator.INFINITE_LOOP_TRAP, block),
+      generator.INDENT,
+    );
+  }
+  const branch = generator.statementToCode(block, 'STACK');
+  let returnValue = generator.valueToCode(block, 'RETURN', Order.NONE) || '';
+  let xfix2 = '';
+  if (branch && returnValue) {
+    // After executing the function body, revisit this block for the return.
+    xfix2 = xfix1;
+  }
+  if (returnValue) {
+    returnValue = generator.INDENT + 'return ' + returnValue + ';\n';
+  }
+  const returnType = returnValue ? 'dynamic' : 'void';
+  const args = [];
+  const variables = block.getVars();
+  for (let i = 0; i < variables.length; i++) {
+    args[i] = generator.getVariableName(variables[i]);
+  }
+  let code =
+    returnType +
+    ' ' +
+    funcName +
+    '(' +
+    args.join(', ') +
+    ') {\n' +
+    xfix1 +
+    loopTrap +
+    branch +
+    xfix2 +
+    returnValue +
+    '}';
+  code = generator.scrub_(block, code);
+  // Add % so as not to collide with helper functions in definitions list.
+  // TODO(#7600): find better approach than casting to any to override
+  // CodeGenerator declaring .definitions protected.
+  (generator as AnyDuringMigration).definitions_['%' + funcName] = code;
+  return null;
+}
+
+// Defining a procedure without a return value uses the same generator as
+// a procedure with a return value.
+export const procedures_defnoreturn = procedures_defreturn;
+
+export function procedures_callreturn(
+  block: Block,
+  generator: DartGenerator,
+): [string, Order] {
+  // Call a procedure with a return value.
+  const funcName = generator.getProcedureName(block.getFieldValue('NAME'));
+  const args = [];
+  const variables = block.getVars();
+  for (let i = 0; i < variables.length; i++) {
+    args[i] = generator.valueToCode(block, 'ARG' + i, Order.NONE) || 'null';
+  }
+  let code = funcName + '(' + args.join(', ') + ')';
+  return [code, Order.UNARY_POSTFIX];
+}
+
+export function procedures_callnoreturn(
+  block: Block,
+  generator: DartGenerator,
+) {
+  // Call a procedure with no return value.
+  // Generated code is for a function call as a statement is the same as a
+  // function call as a value, with the addition of line ending.
+  const tuple = generator.forBlock['procedures_callreturn'](
+    block,
+    generator,
+  ) as [string, Order];
+  return tuple[0] + ';\n';
+}
+
+export function procedures_ifreturn(block: Block, generator: DartGenerator) {
+  // Conditionally return value from a procedure.
+  const condition =
+    generator.valueToCode(block, 'CONDITION', Order.NONE) || 'false';
+  let code = 'if (' + condition + ') {\n';
+  if (generator.STATEMENT_SUFFIX) {
+    // Inject any statement suffix here since the regular one at the end
+    // will not get executed if the return is triggered.
+    code += generator.prefixLines(
+      generator.injectId(generator.STATEMENT_SUFFIX, block),
+      generator.INDENT,
+    );
+  }
+  if ((block as IfReturnBlock).hasReturnValue_) {
+    const value = generator.valueToCode(block, 'VALUE', Order.NONE) || 'null';
+    code += generator.INDENT + 'return ' + value + ';\n';
+  } else {
+    code += generator.INDENT + 'return;\n';
+  }
+  code += '}\n';
+  return code;
+}